FI105199B - Process for producing a binder resin which can be used in an electrophotographic toner - Google Patents

Description

x 105199

A method of producing electrospun color in powder for use as a binder resin

BACKGROUND OF THE INVENTION The present invention relates to a process for preparing a binder resin useful for dry toner powder used in the dry development of a latent electrostatic image for electric photography. In particular, the present invention relates to a process for the preparation of a resin which is partially crosslinked and which has a low crosslinking frequency and a high gel content.

Background of the Invention

Most photocopiers that are useful for office work use the electric photocopy system (15). A typical mechanism of such an electro photography system may be illustrated as follows: The light-conductive layer is sensitized to light by charging it with surface potential; exposing it to light produces a latent electrostatic image of the original image on the light-conducting layer; then charging the toner with a potential having a charge equal to the charge of the latent image; the charged toner is transferred onto the latent image and then again applied to the paper alone by electrostatic force, whereby the toner image is adhered to the paper to produce the desired printed image.

In electric photography, the hot rolled • t · V · 'fixing method has generally been used to attach a toner image to paper alone. The hot roll attachment method 30 comprises transferring a toner image from a surface of a photoconductive photocopier onto a paper only and the image powder is permanently fixed to the paper using a hot roller 120 · · · At a temperature of 180 ° C.

> · •. · Ψ * 1 I · 2 105199 Toner cartridges suitable for use in hot roll bonding are required to soften at relatively low temperatures and to adhere easily to paper (to meet adhesion requirement 5), but do not adhere to hot rolls, even when hot rolls the temperature is relatively high (to have a non-offset feature). The binder resins used in the manufacture of toner powders mainly dictate the aforementioned properties of the toner powders.

Generally, if the melt viscosity of the binder resin used in the toner powder decreases, the adhesion of the toner powder after heat bonding is improved, while the non-offset property of the toner powder is impaired and vice versa. Therefore, many attempts have been made to develop a binder resin capable of satisfying the above requirements satisfactorily for both adhesion and non-offset properties.

U.S. Patent No. 4,486,524 discloses a process comprising the steps of separately producing both a low molecular weight polymer which produces a toner adherence and a high molecular weight polymer which gives the toner a non-offset property, and mixing the polymers so produced. This method improves the adhesion of the toner, but has the wood; * · * · that the toner has a poor non-of f set property and • ·. · **. moreover, it takes a lot of time to produce a high molecular weight ♦ · · polymer and the production costs are high. U.S. Patent No. 4,652,511 discloses a process for producing a resin · · * 30 composition comprising suspension polymerization of at least one vinyl monomer in an aqueous medium in the presence of a dispersant and a high molecular weight vinyl polymer obtained by emulsion polymerization. This method requires a short period of time for the III • · I · «· ·

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3 105199 for resin production, but the non-offset feature remains poor.

JP 134 248/1985, which is disclosed, proposes a biphasic polymerization which produces a polymer having a partially crosslinked structure, i. it has both a crosslinked structure and a pie-molecular weight linear structure. However, in this process, the non-offset property and the bonding ability also tend to deceive each other depending on the crosslinking frequency of the polymer. That is, when the crosslinking frequency of the polymer is low, a suitable gel content cannot be maintained and the non-offset property of the toner powder is poor, even though the adhesion capacity is sufficient. On the other hand, when the crosslinking frequency of the polymer is high, the non-offset propensity becomes acceptable while the bonding ability becomes poor.

Further, EP 412 712 discloses a process comprising the steps of: mixing a low molecular weight resin containing an epoxy group and a virtual crosslinked resin made by adding an unsaturated carboxylic acid to a low molecular weight resin and attaching a multivalent metal; and crosslinking the carboxylic acid with the epoxy group during the doping process to produce a toner powder, to improve the non-25 offset property. However, the apparent crosslinked resin in complex form with a polyvalent metal has poor heat resistance to the doping process.

Mf during the process and in addition, it is difficult to maintain the apparent * ···. the high viscosity of the crosslinked resin, which determines the ability to · · · 30 improve the non-offset property and furthermore the power of the non-offset • • property enhancement tends to be non-uniform due to the non-uniform complexation reaction • during the doping process.

• · · • · «· 1 • · • · 1 v · 1» · · »4 105199

Summary of the Invention

Thus, it is an object of the present invention to provide a process for producing a toner powder resin having both excellent non-offset property and adhesion, method 5 comprising the steps of: producing a polymer having a partially crosslinked structure having both a low crosslinking crosslinked structure and a linear, low molecular weight structure. ; and crosslinking the latex particles to produce a high molecular weight gel 10. The crosslinking of the particles is accomplished during the coagulation process by adding a water-soluble amine to the polymer latex to ion-crosslink the amine to the unsaturated carboxylic acid or to crosslink the amine to a covalently unsaturated monomer containing an epoxy group added to the polymer during the crosslinking. The color powder of the resin of this invention has both excellent adhesion and non-offset properties.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a process for preparing a binder resin useful for producing an electrophotographic toner powder having a partially crosslinked structure comprising both a crosslinked structure and a linear structure, said process comprising the following steps: (1) of crosslinked polymer «·. ···. resin by carrying out a non-crosslinking polymerization which • · ** ·. means an aromatic vinyl monomer, acrylic monomer Ύ. '.' emulsion polymerization of r and cyanide compound to produce a linear * 30 structure; and crosslinking polymerization, which also means emulsion polymerization of an aromatic vinyl monomer, an acrylic monomer, a cyanide compound, and an unsaturated *. monomer containing an unsaturated carboxylic acid or an epoxy group; and the polymer latex obtained in step (1) 105199 (2) is coagulated and crosslinked between the particles using a water-soluble amine.

Generally, polymerization of resins can be carried out using conventional methods such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like. Of these, the emulsion polymerization process is preferred according to the present invention. The novel process of the present invention comprises a two-step polymerization process comprising a first emulsion polymerization process wherein the monomer polymerization produces a linear structure (called a "non-crosslinking step") and a second emulsion polymerization wherein the monomers are crosslinked in the presence of latex 15 obtained in the first step. (this is called the "bridging step"). If desired, the first and second phases can be interchanged.

In the non-crosslinking step, the emulsion polymerizable monomers include an aromatic vinyl monomer, an ac-20 aryl monomer and a cyanide compound. Aromatic vinyl monomer, by copolymerization with acrylic monomer, provides good abrasive electrical property and the ability to control the melting point of the binder resin; and the cyanide compound produces an excellent adhesion of the color to the powder together with the acrylic monomer. Such an aromatic vinyl monomer may be, for example, styrene, · · · t ···. monochloro-styrene, methyl-styrene, dimethyl-styrene, etc. Examples of acrylic monomer may include acrylates such as methyl acrylate, ethyl acrylate, · · · * · 1 · 30 n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, •; and methacrylates, such as methyl methacrylate, ethyl methacrylate and n-butyl.

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. methacrylate. These monomers may be used alone; species, or in combination with one another, in this order. 1, 105199 ο. Examples of the cyanide compound may include acrylonitrile, methacrylonitrile, etc.

The amount of aromatic vinyl monomer in the non-crosslinking step may preferably be from 20 to 90% by weight, more preferably from 35 to 85% by weight, of the total amount of monomers used. Also, the amount of acrylic monomer may preferably be 5 to 60% by weight, more preferably 10 to 50% by weight, and the amount of cyanide compound may preferably be 5 to 50% by weight, and more preferably 10 to 50% by weight of the total amount of monomers. If the amount of aromatic vinyl monomer is less than 20% by weight, the resin color powder is difficult to grind. In addition, if the amount of either the acrylic monomer or the cyanide compound is less than 5% by weight, this results in poor adhesion of the toner powder.

In the polymerization step, a water soluble initiator can be used as the polymerization initiator. Suitable initiators may include persulfates such as potassium persulfate and ammonium persulfate; hydrogen peroxide; reduction-20 oxidation system; and other initiators commonly used in emulsion polymerization. The amount of such an initiator may preferably be 0.05 to 3 parts, more preferably 0.1 to 2 parts, per 100 parts by weight based on the total amount of monomers used in the non-crosslinking step.

In this non-crosslinking polymerization step, anionic or nonionic surfactant can be used. the active substance as an emulsifier. Representative examples of such surfactants may include: alkylaryl sulfonates such as sodium dodecyl benzene sulfonate and potassium dodecylbenzene sulfonate; alkyl sulfonates such as sodium dodecyl sulfonate • · '··· * and potassium dodecyl sulfonate; sulfates such as sodium · · · dodecyl sulfate, sodium octyl sulfate and sodium octadecyl sulfate; a salt of a resin acid such as potassium resin ···. Sodium and sodium resinate; and fatty acid salts such as potassium oleate and potassium stearate. Generally, it may be present in an amount of from 0.1 to 5 parts per 100 parts by weight of the total amount of monomers used.

In addition, mercaptans such as t-dodecylmercaptan and n-dodecylmercaptan may be used as chain transfer agents; terpenes such as dipentene and t-terpene; and halogenated hydrocarbons such as chloroform and carbon tetrachloride. It may conveniently be from 0.05 to 6 parts per 100 parts by weight based on the total amount of monomers.

The non-crosslinking emulsion polymerization can be carried out at a temperature of 40 to 95 ° C, preferably 60 to 85 ° C, for 2 to 15 hours.

Then, in addition to the monomers used in the second polymerization step (the crosslinking step), the unsaturated carboxylic acid or the unsaturated monomer containing the epoxy group should be used in addition to the monomers used in the first step (non-crosslinking step).

Representative examples of unsaturated carboxylic acid may include acrylic acid, methacrylic acid, itaconic acid, maleic acid, citric acid, and fumaric acid. A suitable amount of unsaturated carboxylic acid may be 0.05 to 15% by weight based on the total weight of the monomers used in this step. If its amount is less than 25% 0.05%, the non-off-set property of the toner produced with it will be poor and the amount will be higher • ·. ···. than 15%, the toner adheres poorly.

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Examples of an unsaturated monomer containing an epoxy group may include glycidyl acrylate, glycidyl methacrylate, 4,5-epoxypentyl acrylate. 4,5-epoxypentyl methacrylate, allyl glycidyl ether and butadiene monoepoxide. A suitable amount of the unsaturated monomer containing an epoxy group may be 0.005 to 5% by weight, preferably 0.01 to 3% by weight, of the total amount of monomers used. If the epoxy group contains unsaturated - 105199

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the amount of free monomer is less than 0.05%, the cross-particle cross-linking efficiency is low and, if greater than 5%, the polymerized material has a high melt viscosity and thus the adhesion of the toner powder is poor.

The crosslinking step may be carried out in the presence of a crosslinker using 20 to 85% by weight, preferably 35 to 75% by weight, of aromatic vinyl monomer, 5 to 60% by weight, preferably 10 to 50% by weight of acrylic monomer and 5 to 50% by weight, preferably 10 to 40% by weight of cyanide compounds-10.

Examples of the crosslinker may include vinyl compounds such as divinylbenzene; vinyl aromatic compounds such as divinyl toluene and divinyl xylene; allyl compounds such as N, N-diallyl melamine; allyl-15 livinyl compounds such as allyl acrylate; vinylidene compounds such as ethylene glycol dimethacrylate; and allyl-livinylidene compounds such as allyl methacrylate. The amount of crosslinker may suitably be 0.001 to 4 parts, preferably 0.01 to 3 parts, per 100 parts by weight of the total amount of monomers used. If the amount is less than 0.001 parts, the non-offset property of the toner will be poor and if the amount is greater than 4 parts, the toner will not adhere properly.

The polymerization used in the non-crosslinking step

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25 starters and emulsifiers may also be used,. crosslinking step. In this latter step, a suitable starting amount may be from 0.05 to 3 parts, and a suitable amount of emulsifier may be from 0 to 4 parts per 100 parts by weight of the total amount of monomers used.

The latex produced by the above polymerization steps is then subjected to a coagulation step. In the coagulation step, a mixture of water and coagulant »I *: Itt; stirring in the reactor until a temperature of 60-80 ° C is reached, then latex and amine are added to the reactor.

The coagulant may be, for example, calcium chloride and magnesium sulfide and is present in an amount of 2 to 4 parts by weight per 100 parts by weight of a solid resin.

The amine used in the coagulation step is generally a water-soluble amine and acts to form inter-particle silylation between the latex particles of the resin by reacting with an acid or epoxy group present in the latex particles. The water-soluble amine may be, for example, ethylenediamine, diethylenetriamine, triethylene-tetraamine, tetraethylene-pentamine, and isophorone-10-amine. A suitable amount of water-soluble amine may be 0.01 to 5 parts, preferably 0.05 to 3 parts, per 100 parts by weight of the solid resin. If the amount of amine is less than 0.01 parts, the cross-particle crosslinking reaction may not be sufficient and the resin colored powder may have a poor non-offset property. Although the amount of amine is added to a concentration greater than 3 parts, the cross-particle crosslinking reaction may not increase significantly.

The gel content of the resin represents the concentration of the crosslinked portion 20 in the resin, which can be determined as follows: A suitable amount of the resin is swollen with an organic solvent such as acetone or toluene and centrifuged to separate the gel. The gel thus separated is dried and weighed.

:: The gel content is calculated by dividing the weight of the dried gel by the weight of 25 resins as shown in the following formula: • ·

; ··· :! Gel content <%) - Weight of dried gel χ 10Q

The suitable gel content of the resin of the present invention can be from 15 to 90% and can be controlled by adjusting the resin used in the crosslinking step. and the weight ratio of the resin used in the non-crosslinking 9 m 9 step. If the gel content of the resin is less than 15%, it will eventually ··. The 35 toner powder produced has an inadequate non-of f set property and, if the gel content is greater than 90%, the toner powder may have poor adhesion.

In addition, the linear polymer prepared according to the present invention has a number average molecular weight of 5,000 to 40,000, more preferably 7,000 to 30,000, and a weight average molecular weight of 10,000 to 200,000, more preferably 20,000 to 150,000.

The toner powder may be prepared from the resin of this invention using a method known in the art. For example, 10 parts by weight of a Henschel mixer are mixed with 100 parts by weight of the resin of this invention, 5 parts by weight of carbon black (Regal 300R, Cabot corp. Product), 3 parts by weight of Zappon Fast Black B (BASF product) as a charge control agent and 2 parts by weight of 15 polypropylene waxes. The resulting dry powder is extruded using a twin screw extruder and the extruded product is cooled and finely pulverized by a jet mill to form a 12 micron average powder. The latent electric-20 static image is generated by an electrophotographic copying method using a GCM-8610 made by Gold Star Co., Ltd, Korea.

The properties of toner powder can be determined by evaluating its adhesion to paper, its non-offset property, and the quality of the image produced with the toner. Color ·. ·. the adhesion of the powder can be determined by applying • ·, ···, the adhesive tape to a portion of the copied paper, and then removing • · ** «# it. The degree of damage to the copied portion of the paper is visualized. The non-offset property of the toner • • · 30 can be determined by copying blank paper after 500 copies and observing the formation of black spots · ... 1 on the copied paper due to the adhesion of the toner.

·. ·. ·. The following examples illustrate the present invention in more detail. 35 min without limiting the scope of the invention. All units, pro- • · *

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11 105199 cents, parts, etc., as used in the examples, are by weight unless otherwise indicated.

Example 1

One liter flask was charged with 200 g of water, 3 g of sodium 5-dodecyl sulfate, 0.4 g of potassium persulfate and 3 g of t-dodecyl mercaptan, and 100 g of a monomer mixture consisting of 80% styrene, 15% methyl methacrylate and 5% acrylonitrile for non-crosslinking polymerization. The reaction mixture was polymerized at 60 ° C for 10 hours with stirring.

To the latex thus obtained was added 42.86 g of a monomer mixture consisting of 78% styrene, 10% methyl methacrylate, 5% acrylonitrile and 7% acrylic acid, 0.6 g ethylene glycol dimethacrylate, 90 g: water and 0.15 g potassium persulphate at 60 ° C for 10 hours without interruption.

Then 300 g of the partially cross-linked latex thus prepared was mixed with 3 g of tetraethylene pentamine. The resulting mixture was added to aqueous calcium chloride at 60 ° C for coagulation, and the resulting solution was aged at 70 ° C for 30 minutes. The amount of calcium chloride used was 3 g and the resin so coagulated was filtered and dried to give the resin in powder form. The final resin had a gel content of 30%.

Example 2 The procedures described in Example 1 were repeated except that the non-crosslinking monomer mixture contained 50% styrene, 30% butyl methacrylate and 20% mef. takrylonitriiliä; the monomer mixture in the crosslinking step contained 48% styrene, 30% butyl methacrylate, 18% methacrylic acid, and 4% methacrylic acid; 0.2% divinylbenzene per 100 parts latex was used as the crosslinker, and ethylene diamine was used as the water-soluble amine, 35, 0.6 parts total 100 parts of the solid resin. · · • · «•« · • lii · 12 105199 den. The weight ratio between the monomers used in the crosslinking step and the monomers used in the non-crosslinking step was 60:40. The resulting resin had a gel content of 60%.

Example 3

The procedures described in Example 1 were repeated except that the non-crosslinking monomer mixture contained 25% styrene, 20% butyl acrylate, 15% methyl methacrylate and 40% methacrylonitrile; the monomer mixture in 10 crosslinking steps contained 25% styrene, 20% butyl methacrylate, 15% methyl methacrylate, 30% methacrylonitrile and 10% itaconic acid; 3 parts butylene glycol dimethacrylate was used as a crosslinker for 100 parts of the total amount of monomers used in the crosslinking step, and diethylenetriamine was used as the 15 water-soluble amine per 4 parts of the total amount of the resulting solid resin. The weight ratio of the monomers used in the crosslinking step to the monomers used in the non-crosslinking step was 40:60. The resulting 20 resins had a gel content of 40%.

Example 4

The procedures described in Example 1 were repeated except that the non-crosslinking monomer mixture contained 30% styrene, 50% 2-ethylhexyl acrylate and 25% acrylonitrile; monomer mixture in the crosslinking step. Contains 30% styrene, 49.5% 2-ethylhexyl acrylate, ···, 20% acrylonitrile and 0.5% maleic acid; • 0.01 parts of divinylbenzene were used as the silicone! the total amount of monomers used in the starting step • · · · · · · · · · · · · · · · · “” was used as the water-soluble amine at 0.5 parts per 100 parts of the resulting latex resin. The weight ratio between the monomers used in the crosslinking step and the monomers used in the non-crosslinking step was 75:25. The resulting? · 35 resin had a gel content of 75%.

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Example 5

The procedures described in Example 1 were repeated except that the non-crosslinking monomer mixture contained 45% methylstyrene, 40% ethyl acrylate and 5% methyl acrylate and 10% acrylonitrile; the monomer mixture in the crosslinking step contained 45% methylstyrene, 39% ethylacrylate, 5% methylacrylate, 10% acrylonitrile and 1% methacrylic acid; 0.8 parts of ethylene glycol dimethacrylate were used as a crosslinker per 100 parts of the total amount of monomers used in the crosslinking step; and triethylene tetramlin per 0.8 part of the resulting solid resin was used as the water-soluble amine. The weight ratio of the monomers used in the crosslinking step to the monomers used in the non-crosslinking step was 28: 72. The resulting resin had a gel content of 28%.

Example 6

One liter flask was charged with 200 g water, 2 g potassium oleate and 0.4 g potassium persulfate, and the resulting mixture was stirred. A monomer mixture of 50 g of styrene, 19 g of butyl acrylate, 25 g of methyl methacrylate, 0.1 g of divinylbenzene as a crosslinker and 1 g of glycidyl methacrylate was added thereto, and then the mixture was reacted at 60 ° C for 10 hours with stirring for 25 hours. .

. ·. ·. Thereafter, 300 g of the above-obtained crosslinked latex, 200 g of water and 0.5 g of potassium permulphate sulfate were placed in a 1 liter flask and the resulting mixture was stirred. To the silica was added a monomer mixture of 50 g of styrene, 20 g of butyl acrylate, 25 g of methyl methacrylate and 3 g of carbon tetrachloride, and the mixture was reacted at 60 ° C. · At temperature for 5 hours.

*! ,, / Then 300 g of the thus prepared semi-crosslinker; * ·. This latex (uncrosslinked resin; crosslinked resin * 50 · 50: 50) was mixed with 0.36 g of ethylenediamine.

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The resulting mixture was added to an aqueous solution of calcium chloride at 40 ° C for coagulation and the resulting solution was aged at 60 ° C for 30 minutes. 3 g of calcium chloride were used. The coagulated resin thus obtained was filtered and dried to obtain the resin in powder form.

Example 7

The procedures described in Example 6 were repeated except that the crosslinking step and the non-crosslinking step were interchanged.

Comparative Example 1

The procedures described in Example 1 were repeated except that no water-soluble amine was used during the coagulation process.

Comparative Example 2

The procedures described in Example 1 were repeated except that the composition of the monomer mixture in the crosslinking step was the same as in the non-crosslinking step; i. no acrylic acid.

Comparative Example 3

The procedures described in Example 1 were repeated except that ethylene glycol dimethacrylate was not used as a crosslinker.

Comparative Example 4 The procedures described in Example 6 were repeated except V. that ethylene diamine was not added during the coagulation process.

Comparative Example 5 ··· ···· The procedures described in Example 6 were repeated except that no glycidyl methacrylate was added during the crosslinking step.

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The physical properties and performance of the color powders prepared from the resins obtained in Examples 1-7 and Comparative Examples a5 ′ 1-5 were evaluated and the results are shown in Table 1.

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While the invention has been described in connection with the specific embodiments contained herein, it should be understood that various modifications and changes may be made to those skilled in the art and to which the invention pertains, and are within the scope of the invention as defined by the following claims.

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Claims (9)

A process for preparing a binder resin, characterized in that (1) produces a partially cross-linked polymer by performing: a non-cross-linking polymerization of an aromatic vinyl monomer, an acrylic monomer and a cyanide compound; and a cross-linking polymerization of an aromatic vinyl monomer, an acrylic monomer, a cyanide compound and an unsaturated carboxylic acid or an unsaturated monomer containing an epoxy group; and, then, (2) coagulate the polymer latex obtained in step (1) in the presence of a water-soluble amine. 15 2. A process according to claim 1, characterized in that the unsaturated carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, citraconic acid, fumaric acid and maleic acid. Process according to claim 1, characterized in that the unsaturated carboxylic acid is used in an amount of 0.05 - 15%, calculated on the total weight of monomers, used in the cross-linking polymerization according to step (1). 4. A process according to claim 1, characterized in that the unsaturated monomer containing an epoxy group is selected from the group consisting of glycidyl acrylate, glycidyl methacrylate, 4,5-epoxypentyl glycidyl. Acrylate, 4,5-epoxypentylglycidylmethacrylate, allylglycidyl · ether and butadiene monoepoxide. : * · *: 30 5. A process according to claim 1, characterized in that the unsaturated monomer, as in ···. contains epoxy group, used in an amount of 0.005 - 5%, calculated on the total weight of monomers used in the crosslinking polymerization according to step (1). i · »« «* • · m» • «I * • · 21 105199 6. A process according to claim 1, characterized in that the water-soluble amine is selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentaamine and isophorone diamine. 7. A process according to claim 1, characterized in that the water-soluble amine is used in an amount of 0.01 - 5 parts by weight per 100 parts by weight of resin according to step (1). 10 8. A process according to claim 1, characterized in that the gel content of the binder resin is 15-90% by weight. 9. A process according to claim 1, characterized in that the crosslinking agent in a marrow of 0.001 - 4 parts per 100 parts by weight of the total monomer amount used in the crosslinking polymerization step is used during the crosslinking polymerization according to the step (1). ). I <· 1 1 1 • · I · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 'T »·' I t · t · · f · II t · • · • I * • 1 1 • ·» »'·