JP2759482B2 - Method for producing color toner particles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing color toner particles used in electrophotography, electrostatic printing, and the like.

[Prior Art] Conventionally, many methods are known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. Next, the latent image is developed using toner, and if necessary, a toner image is transferred to a transfer material such as paper.
This is to obtain a copy image.

Conventionally, fine powders in which dyes and pigments are dispersed in a synthetic resin have been used as toners applied to these developing methods. For example, particles obtained by dispersing a colorant in a binder resin such as polystyrene, styrene-acrylic copolymer, or polyester and finely pulverized to about 5 to 20 μm are used as the toner. As the magnetic toner, a toner containing magnetic particles such as magnetite is used. In the case of a system using a so-called two-component developer, the toner is usually mixed with carrier particles such as iron powder, ferrite powder, a resin-coated powder thereof, or a mixture of a resin and a magnetic fine powder. It is used.

[Problems to be Solved by the Invention] Since the toner for electrophotography is adaptable to any environment in which it is used and can be used continuously, it has triboelectric properties, thermal properties, pulverizability, moisture resistance, and powder. Various physical and chemical properties such as fluidity are required. Toners for color electrophotography, which have been attracting attention in recent years, need not only satisfy these properties but, In order to reproduce the image in good quality, it is required that the hue, saturation, transparency, and coloring power of the toner be good.

On the other hand, various dyes and pigments have been used as a colorant that is a material that determines the color of a color toner.
Among them, organic pigments are frequently used for reasons such as sharpness of hue and excellent light fastness.

However, it is not easy to uniformly disperse an organic pigment in a binder resin for a toner. For example, it is difficult to obtain a desired dispersed coloring for a pigment having strong cohesiveness by a normal hot melt kneading method. Also tends to be multi-stage, and the work cost increases.

In particular, in full-color toners whose main characteristic is the melt-mixing of the toner, there is a tendency to select a binder resin having a relatively low viscosity at the time of heat-melting and fixing, which lowers the kneading and dispersing power and is preferred for pigment dispersion. Absent.

Also, in the suspension polymerization method, which is being developed as a method for producing a toner, dispersion of a pigment, particularly dispersion of a pigment in a low-viscosity liquid such as a monomer, has been variously studied. It is insufficient and further improvement is desired.
As described above, for the color toner, improvement in the pigment production process is strongly demanded from the viewpoint of improving the dispersibility of the pigment used.

For example, in the case of a copper phthalocyanine pigment, ordinary crude copper phthalocyanine takes a state of coarse particles of several μm to several tens of μm, and as it is, the color is unclear as it is, and the pigmentation is performed by mechanical or chemical means because of poor coloring power. , To the state of proper particles.

For copper phthalocyanine, chemical pigmentation is generally used, for example, an acid paste method or an acid slurry method.Both are methods in which crude copper phthalocyanine is dissolved in an acid such as sulfuric acid, and this is dispersed in water to obtain fine particles. The particles obtained are of the order of 0.05-1 μm. The finely divided copper phthalocyanine is recovered through an excess / washing / drying process. At that time, the dried and agglomerated particles form coarse agglomerated particles of several tens of μm.

Therefore, when this pigment is used for a toner, coarse particles remain in the toner by ordinary mechanical dispersion means, and as a result, the coloring power of the phthalocyanine pigment is not sufficiently exhibited.

Similarly, when this pigment is used for the production of a toner by a suspension polymerization method, it is difficult to uniformly disperse the pigment in a monomer,
The presence of the coarse particle pigment results in a lack of tinting power, which leads to waste of a large amount of pigment and a decrease in transparency. Further, non-uniform dispersion in toner particles or variation among toner particles leads to non-uniformity of toner characteristics.

In general, many pigments themselves have a certain degree of triboelectricity, and uneven dispersion of the pigment in the toner causes instability of triboelectricity of the toner, and the distribution of triboelectrification is broadened, resulting in an increase in the electronic charge. It has a great effect on photographic developability and leads to defects such as development fog and scattering.

As in this example, in the case of many organic pigments produced by a water washing and drying process via an aqueous medium system, aggregation during the production process is an important problem.

An object of the present invention is to provide a method for producing color toner particles for use in electrophotography, which solves the above-mentioned problems.

That is, it is an object of the present invention to provide a method for producing color toner particles in which the dispersion of the colorant in the toner is uniform, the triboelectricity of the toner particles is uniform and stable, and the coloring power, transparency and chroma are high.

Another object of the present invention is to provide a method for achieving a pigment dispersion in a suspension polymerization method much more efficiently and well than before.

[Means and Actions for Solving the Problems] That is, the present invention provides a method of polymerizing an organic pigment from an aqueous phase by mixing a water-containing cake or an aqueous dispersion of the organic pigment with a polymerizable monomer and then performing a flushing treatment. And (c) polymerizing (a) an organic pigment monomer dispersion, (b) a polar polymer, a polar copolymer or a cyclized rubber, and (c) a polymerization. The initiator and the initiator are dissolved and dispersed while heating to prepare a polymerizable monomer composition, and the obtained polymerizable monomer composition is dispersed in a heated aqueous medium and polymerized. The present invention relates to a method for producing color toner particles, which comprises producing particles of a monomer composition, and polymerizing polymerizable monomers in the particles of the polymerizable monomer composition to produce color toner particles.

The present invention does not dry an aqueous dispersion or a water-containing cake of finely divided organic pigments pigmented in an aqueous medium as usual, but directly mixes them in a polymerizable monomer to form a finely divided organic pigment. By dispersing and dispersing in the monomer phase without aggregating, it is possible to improve the state of dispersion much more than the conventional method of mechanically dispersing the dried and aggregated pigment in the monomer, and This is based on the finding that the polymerization color toner obtained by the method is excellent in coloring property and triboelectric charging property.

The aqueous dispersion of the pigmented fine organic pigment is dehydrated by, for example, a filter press or the like to become a concentrated liquid having a water content of 60 to 80% by weight. The water-containing cake is mixed with the monomer to obtain a water / monomer dispersion of the pigment. The mixing ratio of the monomer and the pigment dispersion or the water-containing cake depends on the amount of the pigment required in the finally obtained toner, but is 5 to 200 parts by weight per 100 parts by weight of the monomer. It is blended in the range. At this stage, the pigment migrates from the aqueous phase to the monomer phase as fine particles due to its lipophilic property, and is uniformly dispersed in the monomer phase.

At this time, if the blending amount of the pigment with respect to the monomer exceeds this range, the amount of the pigment in the toner becomes excessive and the sharpness of the coloring is reduced, which affects the triboelectric charging property of the toner. On the other hand, if the ratio is below this range, the pigment becomes insufficient and the coloring power is reduced. The amount of the pigment finally required in the toner is generally 1 to 20% by weight, more preferably 2 to 15% by weight, based on the toner.

The monomer phase in which the pigment is dispersed is separated from the aqueous phase, and an anti-offset agent necessary for forming a toner in the monomer phase,
A charge control agent, an additional colorant, and the like are added, and further, additives necessary for a polymerization reaction for obtaining a polymerized toner, for example, in the case of vinyl polymerization, a polymerization initiator, a crosslinking agent, a molecular weight modifier, and the like.

The colored particles obtained by the polymerization method can be obtained by, for example, the following method, but are not limited thereto. An aqueous medium containing a suspension stabilizer containing a monomer system obtained by uniformly dissolving or dispersing a polymerizable monomer, a colorant, a polymerization initiator and, if necessary, a crosslinking agent, a charge control agent, a polar polymer, and other additives ( That is, it is charged into the continuous phase) and granulated and polymerized with stirring. Thereafter, the suspension stabilizer is removed, separated and dried.

It is particularly preferable to obtain colored particles by such a suspension polymerization method because the particle size distribution is sharp.

Polymerizable monomers that can be applied to form the polymerized colored particles are monomers having a CH ₂ ＣC <group as a reactive group, and include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methylstyrene. -Methoxystyrene, p-
Styrene such as ethylstyrene and its derivatives: acrylic acid, methacrylic acid, maleic acid, maleic ester:
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate Methacrylates such as aminoethyl and diethylaminoethyl methacrylate: methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-acrylate
Acrylic esters such as octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate: vinyl such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide There are monomers having a reactive double bond such as a group. These may be used alone or in combination of two or more. If necessary, a cross-linking agent may be used. As a crosslinking agent,
Examples thereof include divinylbenzene, divinylnaphthalene, diethylene glycol dimethacrylate, and ethylene glycol dimethacrylate. The amount of the crosslinking agent to be added is generally 0.1 to 5 parts by weight based on 100 parts by weight of the polymerizable monomer. Further, a small amount of a polymer of these polymer monomers may be added to the monomer composition. Among the above-mentioned monomers, styrene, styrene having a substituent such as an alkyl group, or polymerized colored particles produced from a mixed monomer of styrene and other monomers have developability and durability. It is preferable when considering it.

Further, a preferable polymerized toner can be obtained by adding a polar polymer having a polar group, a polar copolymer or a cyclized rubber as an additive during polymerization of the monomer to polymerize the polymerizable monomer. The polar polymer, polar copolymer or cyclized rubber is added in an amount of 0.5 to 50 parts by weight, preferably 1 to 40 parts by weight, based on 100 parts by weight of the polymerizable monomer. If the amount is less than 0.5 part by weight, it is difficult to obtain a sufficient pseudo-capsule structure. If the amount is more than 50 parts by weight, the amount of the polymerizable monomer becomes insufficient and the characteristics as a polymerized toner tend to deteriorate. A polymerizable monomer composition to which a polar polymer, a polar copolymer or a cyclized rubber is added is suspended in an aqueous phase of an aqueous medium in which the polar polymer and a reverse-charged dispersant are dispersed, and polymerized. Preferably. That is, the cationic or anionic polymer, the cationic or anionic copolymer or the cyclized rubber contained in the polymerizable monomer composition is a reverse-charged anionic or dispersed in an aqueous medium. The cationic dispersant is electrostatically attracted to the toner particle surface, and the dispersant covers the particle surface to prevent coalescence and stabilization of the particles, and to add the added polar polymer, polar copolymer or ring. Since the fluorinated rubber is collected on the surface layer of the toner particles, it forms a kind of shell, and the obtained particles become pseudo capsules. The relatively high molecular weight polar polymer, polar copolymer or cyclized rubber collected on the surface layer of the particles contains a large amount of a low softening point compound inside the toner particles. , Developing property and abrasion resistance. The polar polymer (including the polar copolymer and the cyclized rubber) and the reverse charge dispersant which can be used in the present invention are exemplified below. The polar polymer having a weight average molecular weight of 5,000 to 500,000 as measured by GPC is preferably used because it is well dissolved in the polymerizable monomer and has durability.

(I) Examples of the cationic polymer include a polymer of a nitrogen-containing monomer such as dimethylaminoethyl methacrylate and diethylaminoethyl acrylate, a copolymer of styrene and the nitrogen-containing monomer, styrene, and an unsaturated carboxylic acid ester. And the nitrogen-containing monomer.

(Ii) as the anionic polymer, a polymer of a nitrile monomer such as acrylonitrile, a polymer of a halogen-containing monomer such as vinyl chloride, a polymer of an unsaturated carboxylic acid such as acrylic acid or methacrylic acid, There is a polymer of an unsaturated dibasic acid, a polymer of an anhydride of an unsaturated dibasic acid, or a copolymer of styrene and the monomer.

As the dispersant, an inorganic fine powder which has the ability to stabilize the dispersion of the monomer composition particles in an aqueous medium and is hardly soluble in water is preferred. The amount of the dispersant added to the aqueous medium is preferably 0.1 to 50% by weight (preferably 1 to 20% by weight) based on water.

(Iii) Aerosil # 200,
There is colloidal silica such as # 300 (produced by Nippon Aerosil Co., Ltd.).

(Iv) Examples of the cationic dispersant include aluminum oxide, magnesium hydroxide, and hydrophilic positively chargeable silica fine powder such as aminoalkyl-modified colloidal silica treated with a coupling agent.

A cyclized rubber having anionic property may be used instead of the above-mentioned polar polymer or copolymer.

The suspension polymerization method is, as described in Examples below, a polymerizable monomer composition obtained by uniformly dissolving and dispersing a coloring agent or an additive added as necessary, 0.1 to 50% by weight. Aqueous medium containing a suspension stabilizer (eg, a poorly soluble inorganic dispersant) (eg, 5 ° C. or higher than the polymerization temperature, preferably
(Heated to a temperature of 10 ° C. to 30 ° C. or more) using a conventional stirrer, homomixer, homogenizer, or the like. Preferably, the particles of the polymerized monomer composition that has been melted or softened have a desired toner particle size, generally
The stirring speed, time and temperature of the aqueous medium are adjusted so as to have a size of 30 μm or less (for example, a volume average particle size of 0.1 to 20 μm). Thereafter, the temperature is lowered to the polymerization temperature of the liquid temperature of the aqueous medium while stirring the particles so as to prevent sedimentation of the particles so that the state is substantially maintained by the action of the dispersion stabilizer. The polymerization temperature is set at 50 ° C. or higher, preferably 55 to 80 ° C., particularly preferably 60 to 75 ° C., and the polymerization is carried out with stirring.
After the completion of the reaction, the produced toner particles are recovered by an appropriate method such as washing, removal of the dispersion stabilizer, excess, decantation, centrifugation and the like, and dried to obtain polymerized colored particles usable in the present invention. In the suspension polymerization method, usually 100 parts by weight of a polymerizable monomer and a low softening point compound are added to 200 parts of water.
30003000 parts by weight are used as aqueous medium.

In the present invention, waxes generally used as an anti-offset agent, such as a hydrocarbon compound, may be blended with the monomer system in order to improve the anti-offset property at the time of fixing the toner with a hot roll.

The hydrocarbon compound that can be used in the present invention has a melting point.
Paraffinic hydrocarbons in the range of 55 to 70 ° C are preferably used. For example, as paraffin wax, there are products manufactured by Japan Petroleum and Nippon Seiwa, and as branched paraffin wax, there are microcrystalline wax (manufactured by Nippon Seiwa) and micro wax (manufactured by Nippon Oil).

The amount of the wax added is preferably 1 to 30 parts by weight based on 100 parts by weight of the polymer.

As the polymerization initiator, any suitable polymerization initiator, for example, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile,
An azo or diazo type such as 1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and other azobisisobutyronitrile (AIBN) Polymerization initiators: peroxide-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorylbenzoyl peroxide and lauryl peroxide. Generally, about 0.5 to 10% of these polymerization initiators by weight of the polymerizable monomer is sufficient.

As the organic pigment used in the present invention, a pigment having lipophilicity is preferable among those which are finally produced in an aqueous medium system and are made into a product through an overdrying step. The method of the present invention, in principle, utilizes the transfer of the pigment from the water phase to the oil phase, so the pigment requires lipophilicity. It can be used after being made lipophilic by surface treatment. For example, lipophilic pigments such as benzidine yellow and the above-mentioned copper phthalocyanine can be transferred to the oil phase very easily. Preferred types of pigments can be selected from a wide range of azo lake pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, quinacridone pigments and the like.

The pigment used may be in the form of a suspension having a low dehydration rate or a hydrated cake (press cake) having an increased dehydration rate, and since the aqueous phase after transfer of the pigment is separated and removed, it is used. Water washing of press cakes and the like does not require strictness. That is, since the hydrophilic substance used in the pigment production process is removed together with the water, the incorporation of a hydrophilic substance which greatly affects the moisture resistance of the toner can be avoided.

In addition to the organic pigment used by the method of the present invention, a colorant generally used for a toner can be used in combination, and can be used in a form mixed with a monomer phase. In this case, for the purpose of the present invention, it is premised that the dispersion in the monomer phase is good, and it is selected from those which are not likely to be transferred to the aqueous phase.

On the other hand, as the charge control substance to be added as necessary, among those generally known, anhydrous or pale color,
Those that do not affect the hue and saturation of the color toner are selected.

For example, metal complexes of salicylic acid and dialkylsalicylic acid, or metal complexes of various derivatives having a parent structure of salicylic acid are preferable.

Fine particles may be added and mixed (externally added) to the obtained toner particles for the purpose of improving fluidity.

Examples of the fluidity modifier include colloidal silica, Teflon fine particles, and alumina fine particles.

These are preferably blended in the range of 0.2 to 15% by weight based on the toner particles.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples. The parts in the following formulations are parts by weight.

Example 1 Copper phthalocyanine blue water-containing cake (water content 70%)
35 parts, 170 parts of styrene and 30 parts of 2-ethylhexyl acrylate were mixed and stirred to transfer copper phthalocyanine to the monomer phase. Thereafter, the mixture was allowed to stand and separated, and then an aqueous phase and a monomer phase were separated and separated to obtain a monomer pigment dispersion. To 200 parts of the obtained monomer pigment dispersion, a styrene-methacrylic acid copolymer (monomer ratio: 90/10, weight average molecular weight: 5.6
10 parts, paraffin wax T-550 (Taisei Kosan,
30 parts of melting point 155 ° F), 2 parts of chromium complex of di-tert-butylsalicylic acid, and 10 parts of polymerization initiator (V-601) were mixed,
The mixture was heated to ℃, dissolved and dispersed to prepare a polymerizable monomer composition.

Separately, an aqueous medium was prepared. That is, ion-exchanged water
To 1200 parts, 0.25 parts of γ-aminopropyltrimethoxysilane, 10 parts of colloidal silica # 200 (manufactured by Nippon Aerosil), and the mixture was heated to 60 ° C., and TK homomixer M was added.
Using a mold (manufactured by Tokushu Kika Kogyo Co., Ltd.), the mixture was dispersed at 10,000 rpm for 15 minutes. Further, 1 / 10N-HCl was added to adjust the pH of the system to 6 to prepare an aqueous medium.

The polymerizable monomer composition was charged into the obtained aqueous medium, heated to 60 ° C. under a nitrogen atmosphere, and using a TK homomixer.
The polymerizable monomer composition was suspended in an aqueous medium by stirring at 6,500 rpm for 60 minutes. The size of the droplets of the polymerizable monomer composition in the suspension system was approximately 8 to 13 microns under a microscope, and the particle size distribution was well uniform.

Next, the suspension having the droplet particles of the polymerizable monomer composition is transferred to a reaction vessel having a paddle stirring blade, and stirred.
The polymerization was completed at 70 ° C. for 20 hours.

After completion of the polymerization, the reaction product was cooled, a 20% aqueous NaOH solution was added to dissolve the dispersant, and filtration and washing were repeated, followed by drying to obtain cyan polymerized toner particles.

To 100 parts of the toner, 0.6 part of colloidal silica (T-500, manufactured by Talco) as a fluidity imparting agent was added,
A developer was prepared by mixing 8 parts of the silica-added toner and 92 parts of a carrier obtained by coating the surface of ferrite particles having an average particle diameter of 50 μm with styrene-acrylic resin.

Using this developer, a copy test was performed with a Canon CLC-1.
6) was obtained, and there was no problem of fogging and scattering.

Example 2 180 parts of styrene, 20 ethyl 2-hexyl acrylate
Part, quinacridone magenta water-containing cake (water content 80%)
50 parts are mixed and stirred to transfer to the quinacridone magenta monomer phase, and then separated by standing, removing the aqueous phase to obtain a pigment monomer dispersion. 200 parts of the obtained dispersion, styrene-
10 parts of methacrylic acid copolymer (monomer ratio 90/10, weight average molecular weight 56,000), 2 parts of chromium complex of di-tert-butylsalicylic acid, paraffin wax T-550 (manufactured by Taisei Kosan,
20 parts of a melting point of 155 ° F.) and 10 parts of a polymerization initiator (V-601) were mixed, heated to 60 ° C., dissolved and dispersed to prepare a monomer system.

Separately, 0.5 parts of γ-aminopropyltrimethoxysilane and 10 parts of colloidal silica # 200 (manufactured by Nippon Aerosil) are added to 1200 parts of ion-exchanged water and heated to 60 ° C., and a TK homomixer M type (manufactured by Tokushu Kika Kogyo) ) At 10,000 rpm for 15 minutes. Further, 1/10 HCl was added to adjust the system to pH 6, and a dispersion medium system was prepared. The monomer system was charged into the obtained dispersion medium system, and suspension polymerization was performed in the same manner as in Example 1 under a nitrogen atmosphere.

After completion of the polymerization, the reaction product was treated with a 20% aqueous NaOH solution to dissolve and remove silica as a dispersing agent, washed repeatedly with water, and dried to obtain magenta polymerized toner particles.

The obtained magenta toner particles had a volume average diameter of 10.8 μm as measured by a Coulter counter.

0.5 part of colloidal silica (T-500) was added to 100 parts of the toner particles, and 10 parts of the silica-added toner and 90 parts of a carrier were mixed to prepare a two-component developer.

The blow-off charge amount of the silica-added toner with respect to iron powder (EFV 200/300) was −23 μc / g.

Using this developer, an image was formed with a Canon CLC-1 color copier. As a result, a sufficient image density (1.42) was obtained, and no fog or scattering was observed.

Comparative Example 1 A dispersion was prepared by mixing and stirring 10 parts of copper phthalocyanine blue pigment powder, 170 parts of styrene, and 30 parts of 2-ethylhexyl acrylate which had been subjected to a normal dehydration / drying step. 200 parts of the obtained pigment-dispersed monomer liquid, 30 parts of paraffin wax T-550, 2 parts of a chromium di-tert-dibutylsalicylate complex, and 10 parts of an initiator (V-601) were mixed, and the mixture was heated to 60 ° C and dissolved. Dispersion gave a monomer system.

Thereafter, polymerization was carried out in the same manner as in Example 1 to obtain a cyan polymerized toner and a two-component developer.

An image was formed using this developer in the same manner as in Example 1. As a result, a low image density (1.12), which was judged to be due to insufficient coloring power of the toner, was observed.

Example 3 Instead of the water-containing cake of the pigment of Example 1, a water-containing cake of CI Pigment Yellow 12 (water content: 70%) was used, and a further 20 parts of a cyclized rubber (Alpex CK- 514, manufactured by Hoechst Co.), and yellow polymerized toner particles were obtained in the same manner as in Example 1. Further, a sufficient image density (1.43) was obtained by the same image test as in Example 1, and there was no problem in image quality.

[Effects of the Invention] As described above, the method for producing color toner particles of the present invention comprises:
Because the pigment is well and uniformly dispersed in the color toner particles, the coloring power of the color toner, that is, the coloring power when the toner is thermally fixed on the support, the sharpness, and the saturation, are excellent, and the toner is triboelectrically charged. Color toner particles having uniform properties and capable of forming an image with excellent image quality can be produced.

Claims (3)

(57) [Claims] An organic pigment is mixed with a water-containing cake or aqueous dispersion of an organic pigment and a polymerizable monomer and then subjected to a flushing treatment to transfer and disperse the organic pigment from an aqueous phase into a polymerizable monomer phase. Obtaining a pigment monomer dispersion, (a) an organic pigment monomer dispersion, and (b) a polar polymer,
The polar copolymer or cyclized rubber and the polymerization initiator (c) are dissolved and dispersed while heating to prepare a polymerizable monomer composition, and the obtained polymerizable monomer composition is Is dispersed in a heated aqueous medium to produce polymerizable monomer composition particles, and polymerizable monomers in the polymerizable monomer composition particles are polymerized to produce color toner particles. A method for producing color toner particles. 2. The process for producing color toner particles according to claim 1, wherein the polar polymer, polar copolymer or cyclized rubber is used in an amount of 0.5 to 50 parts by weight based on 100 parts by weight of the polymerizable monomer. . 3. The method according to claim 1, wherein the polar polymer or polar copolymer has a weight average molecular weight of 5,000 to 500,000.