JPH11292922A - Filtration of latex and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently filtrating latex by using a specific filtrating material and giving a quick reciprocating motion to the filtrating material. SOLUTION: This method for filtrating butadiene-based latex is performed by using a plane woven wire gauze made of a stainless steel and having a 1-150 μm aperture, a sintered metal body having 1-150 μm maximum pore diameter or an electric sieve having 1-150 μm aperture and filtrating the latex under 0.005-15 kg/cm<2> gauge pressure while giving a vibration (reciprocal motion) at a 3-20 deg. amplitude, 10-120 Hz frequency and >=20 cm/sec average velocity in a peripheral direction of the filtrating material. The method is industrially useful because of efficiently filter the latex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filtering latex. More specifically, the present invention relates to a method for efficiently filtering latex by using a specific filter medium and giving the filter medium a high-speed reciprocating motion.

[0002]

2. Description of the Related Art Conventionally, it has been obtained by emulsion polymerization of polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, carboxylic acid or vinylpyridine-modified styrene-butadiene polymer latex, and the like. Latex is widely used as a binder for paper coating, fiber treatment, or tire cord treatment, and as a rubber component of a rubber-reinforced resin.

[0003] These conjugated diene-based polymer latexes are mainly composed of particles having a particle size of 0.05 to 1 µm. However, due to the generation of fine coagulates during polymerization, polymer particles having a particle size of 1 µm or more are produced. That is, it also contains giant particles.

The large particles having a size of 1 μm or more adversely affect the quality of the obtained latex.
In the field of paper coating, when a latex containing a large amount of these giant particles is used as a binder, for example, mechanical dirt (streak trouble etc.) at the time of paper coating, strength reduction at coated paper, etc. There were various problems. Therefore, various studies have been made to remove these giant particles.

For example, Japanese Patent Publication Nos. 46-32058 and 3-65820 propose a method of filtering using diatomaceous earth.

However, in these methods, a part of the latex is incorporated into the layer of diatomaceous earth by filtration, and diatomaceous earth containing a large amount of latex remains after filtration. And there was also a problem in terms of product yield.

Further, in the conventional method using a filter medium such as filter paper, filter cloth, wire mesh, etc., the latex has high tackiness and easily clogs, so that it is practically impossible to perform filtration.

[0008]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have focused on and studied a filter medium used for filtration. As a result, a specific filter medium was used, and a high-speed filter medium was used. By giving a reciprocating motion and filtering under pressure, a method capable of efficiently filtering latex was found, and the present invention was completed.

That is, in the present invention, a metal filter medium is used, and the filter medium has an average speed of 20 cm in a direction parallel to the surface of the filter medium.
/ Reciprocating motion more than / s and at gauge pressure 0.00
It is intended to provide a method for filtering latex, characterized by filtering under pressure of 5 to 15 kg / cm2.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, the latex subjected to filtration is a natural latex or a synthetic latex, and examples of the synthetic latex include a conjugated diene-based polymer latex, an acrylic latex, a chloroprene-based latex, a vinyl acetate-based latex, and a vinyl chloride-based latex. Conjugated diene monomer alone or another monomer copolymerizable therewith, such as an ethylenically unsaturated carboxylic acid monomer, an aromatic vinyl monomer, or a vinyl cyanide monomer. Mers,
Those obtained by emulsion polymerization of an unsaturated carboxylic acid alkyl ester monomer, an unsaturated monomer containing a hydroxyalkyl group, an unsaturated carboxylic acid amide monomer, a maleimide-based monomer and the like are preferable.

Examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, and 2,3-butadiene.
Examples thereof include dimethyl-1,3 butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and one or more kinds thereof can be used. In particular, 1,3-butadiene is preferred.

The aromatic vinyl monomers include styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyl toluene and divinyl benzene, and the like,
One or more kinds can be used. Particularly, styrene is preferred.

Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like, and one or more kinds can be used. Particularly, acrylonitrile and methacrylonitrile are preferred.

Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Two or more types can be used. Particularly, mono- or dicarboxylic acids are preferred.

The unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl maleate Examples include itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate, and the like, and one or more kinds can be used. Particularly, methyl methacrylate is preferred.

As unsaturated monomers containing a hydroxyalkyl group, β-hydroxyethyl acrylate, β
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate,
Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl)
Maleate, 2-hydroxyethyl methyl fumarate and the like can be mentioned, and one kind or two or more kinds can be used. Particularly, β-hydroxyethyl acrylate is preferable.

The unsaturated carboxylic acid amide monomers include:
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Acrylamide is particularly preferred.

As the maleimide-based monomer, maleimide, N-phenylmaleimide, N-methylmaleimide,
N-cyclohexylmaleimide and the like can be mentioned, and one kind or two or more kinds can be used. Particularly, N-phenylmaleimide is preferred.

In addition to the above-mentioned monomers, any of the monomers used in ordinary emulsion polymerization, such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl pyridine, vinyl chloride, and vinylidene chloride, can be used. It is.

Of the above polymerizable monomers, it is preferable to use a conjugated diene monomer alone or a monomer copolymerizable therewith.
% By weight, ethylenically unsaturated carboxylic acid monomer 0.5 to 1
0% by weight and monomers copolymerizable therewith (most preferably containing an aromatic vinyl monomer, a vinyl cyanide monomer, an unsaturated carboxylic acid alkyl ester monomer, a hydroxyalkyl group One or two or more monomers selected from the group consisting of unsaturated monomers, unsaturated carboxylic acid amide monomers, and maleimide monomers) 10 to 89.5% by weight
It is preferable to use a monomer consisting of

The solid content concentration and the number average particle size of the conjugated diene polymer latex to be subjected to the filtration of the present invention are not particularly limited, but preferably the solid content concentration is 30 to 70% by weight, The particle size is 50 to 300 nm. Also,
There is no particular limitation on the gel content of the polymer latex,
When the latex after purification by filtration is used as a binder for offset rotary printing paper, the gel content is preferably 10 to 6% by weight.
It is preferably 0% by weight.

As the metal filter medium used in the filtration method of the present invention, a filter medium having a small thickness, a large aperture ratio, and a uniform opening is preferable. Such a filter medium is preferably a woven wire mesh, a sintered metal body, or an electric sieve.

The woven wire mesh used in the present invention is preferably an woven wire mesh having an aperture size of 1 to 150 μm. The weaving method of the wire mesh may be plain weave, twill weave, plain tatami weave or any other weave. In the case of weaving methods other than plain weaving and twill weaving, the aperture is not usually measured, and in this case, the reference value (Nominal Microns) of the passing spherules corresponds to the aperture. In the woven wire mesh used in the present invention, the wire diameter is preferably smaller, but is not particularly limited, and the wire is also preferably a stainless steel, but may be selected according to use conditions, There is no particular limitation.

When a sintered metal body is used as the filter medium, the pore diameter is not uniform, but the maximum pore diameter defined by the manufacturer of the filter medium of the sintered metal body in a similar manner to the woven wire mesh is 1 to 150.
μm is preferred. Here, the maximum pore diameter is a value calculated based on the initial bubble point pressure Pa obtained by the bubble point pressure measuring method. The porosity of the filter medium of the sintered metal body used in the present invention is preferably as large as possible, but is not particularly limited. Further, the wire diameter is desirably small, but is not particularly limited. Further, the wire is preferably a stainless steel, but may be selected according to the use conditions, and is not particularly limited. As for the filter media of these sintered metal bodies, there are also sintered metal bodies having different maximum pore diameters or those having a multilayer structure of two or more layers used in combination with a woven wire mesh, in which case the finest maximum pore diameter is 1-150 μm
If it is within the range, there is no problem in use in the present invention.

The electroformed sieve used in the present invention is a net made by an electrochemical method. The opening is preferably 1 to 150 μm. The thickness, aperture ratio, and material of the electric sieve used in the present invention may be selected according to the conditions of use, and are not particularly limited.

As the metal filter medium, a commercially available filter medium such as a punched metal, a wedge wire screen and the like can be used in addition to the woven wire mesh, the sintered metal body, and the electric sieve.

The opening and the maximum pore size of the filter medium used for filtering the latex of the present invention are preferably from 1 to 150 μm, but the number average particle diameter of the latex to be filtered and the content of macroparticles of 1 μm or more are contained. Although it is appropriately set depending on the amount, it is preferably 1 to 40 μm.

In the filtration of the present invention, a gauge pressure of 0.
It is necessary to filter under a pressure of 005 to 15 kg / cm2. If the gauge pressure is less than 0.005 kg / cm 2, the filtration speed is too slow, and the gauge pressure is 15 k / cm 2.
If it exceeds g / cm 2, the load on the filter medium becomes too large, and good filtration cannot be performed.

At the time of filtration, in order to prevent clogging of the filter medium and maintain an appropriate filtration speed, it is necessary to give the filter medium a reciprocating motion at an average speed of 20 cm / sec or more in a direction parallel to the filter medium surface. However, if the average speed is less than 20 cm / sec, it is not preferable because sufficient filtration targeted in the present invention cannot be performed. Further, the higher the average speed is, the higher the filtration efficiency is. However, if the average speed exceeds a certain range, further improvement of the filtration efficiency cannot be expected. Conversely, the energy required for filtration increases, and the load on the filtration device also increases. Therefore, the average speed is preferably set to 20 to 2000 cm / sec, and more preferably 100 to 1000 cm / sec, because it is economically disadvantageous in terms of durability.

In particular, in the present invention, a disk-shaped filter medium is used as the filter medium, and the filter medium has an amplitude of 3 to 20 degrees in a circumferential direction in a horizontal plane of the filter medium, an average speed of 20 cm at a vibration frequency of 10 to 120 Hz. By giving a reciprocating motion of at least / sec, the filtration of the latex can be performed efficiently, which is preferable. At this time, the average speed (u) is u = 2πr ×
(A / 360) × 2b [where r is the radius of the disc-shaped filter medium ×
1/2, a is the amplitude (degree), and b is the vibration frequency (hertz). ]. The average speed is appropriately set according to the size, amplitude, and vibration frequency of the disk-shaped filter medium used.

Incidentally, within a range not to impair the effects of the present invention,
Vibration may be applied in the vertical direction in addition to the reciprocating motion described above.

According to the filtration method of the present invention, the latex is
It is divided into two types: a purified latex that has passed through the filter medium and a latex containing macroparticles that cannot pass through the filter medium, that is, a filtration residue. This filtration residue is present on the filter medium in the filtration step, or is once transferred from the filter medium to another place, and then sent again to the filter medium, and filtered under the specific conditions of the present invention. It will be continued. For this reason, the filtration residue preferably has a certain degree of fluidity. In order to have preferable fluidity, it is preferable that the amount of macroparticles of 1 μm or more in the filtration residue is 20% by weight or less.

In the filtration method of the present invention, a filter aid can be used. That is, by mixing a filter aid such as diatomaceous earth or perlite with the latex, and then filtering the mixture by the filtration method of the present invention, an effect of preventing clogging during the filtration is preferable. As a filter aid, diatomaceous earth is preferable, and it is preferable to use 0.001-2 parts by weight based on 100 parts by weight of the latex solution.

The latex to be subjected to the filtration method of the present invention can be produced by emulsion polymerization. In this case, a usual emulsifier, polymerization initiator, electrolyte, chain transfer agent, polymerization accelerator, chelating agent and the like are used. can do.

Examples of the emulsifier include anionic salts such as sulfates of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, and sulfate salts of nonionic surfactants. A surfactant or a nonionic surfactant such as an alkyl ester type, an alkyl phenyl ether type or an alkyl ether type of polyethylene glycol is used alone or in combination of two or more.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate, and sodium persulfate, a redox initiator, or an oil-soluble initiator such as benzoyl peroxide can be used.

Examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, dimethyl xanthogen disulfide, and diisopropyl xanthogen. Xanthogen compounds such as disulfide, thiuram-based compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide and tetramethylthiuram monosulfide;
-Di-t-butyl-4-methylphenol, phenolic compounds such as styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane,
Halogenated hydrocarbon compounds such as carbon tetrachloride and carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, α-methylstyrene dimer, terpinolene, triphenylethane, pentane Phenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate and the like can be mentioned, and one or more kinds can be used.

In the above emulsion polymerization, for example, cyclopentene, cyclohexene, cycloheptene,
The polymerization may be carried out in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring such as -methylcyclohexene or 1-methylcyclohexene or a hydrocarbon such as benzene, toluene, hexane or cyclohexane. At this time, the used amount of the hydrocarbon is 0.1 to 30 parts by weight based on 100 parts by weight of the monomer.

1 μm purified by the filtration method of the present invention
Latex from which the content of macroparticles of m or more has been removed to less than a certain ratio is used as a binder in various applications. In particular, latex containing less than 0.5% by weight is used as a binder for paper coating. It is preferably used as

[0040]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless the gist of the present invention is changed. In the examples,
Parts and percentages indicating percentages are based on weight. Unless otherwise specified, the weight% is based on the latex liquid, and the total of the liquid content and the solid content is 100% by weight.
The measurement of various physical properties in Examples and Comparative Examples was based on the following methods.

Average particle diameter The number average particle diameter was measured by a dynamic light scattering method. In the measurement, LPA-3000 / 3100 (manufactured by Otsuka Electronics) was used.

Gel content The latex is dried at room temperature to prepare a latex film. Then, about 0.2-0.3 latex film
Weigh g exactly. After being immersed in 200 cc of toluene for 48 hours, the residue was filtered through a 300-mesh wire gauze, and the dry weight of the residue (toluene-insoluble matter) on the wire gauze was determined.

Measurement of Amount of Giant Particles 500 g of a latex sample was filtered through a (1) # 500 wire mesh to determine the solid content (ag) of the macroparticles remaining on the mesh. (2) Using a scanning electron microscope, the number of particles and the volume average particle diameter of macroparticles of 1 μm or more were determined from the filtrate filtered through a wire mesh of # 500, and its specific gravity was set to 1 and its weight (b)
g) is calculated. Giant particle amount (% by weight) = (a + b) ÷
It is determined as 500 × 100.

Polymerization of copolymer latex Polymer latex A: 100 parts of water, 100 parts of water, 0.2 parts of sodium dodecylbenzenesulfonate, 0.3 parts of sodium hydrogencarbonate, 1.0 parts of potassium persulfate and 1 part in an autoclave. , 3-butadiene 40 parts, styrene 49 parts and methyl methacrylate 5 parts, fumaric acid 2
Parts, 1 part of acrylic acid, 2 parts of β-hydroxyethyl acrylate, and 1 part of acrylamide, and 0.75 part of t-dodecylmercaptan as a chain transfer agent, and polymerization was carried out at 70 ° C. to give a polymerization conversion of 97 parts. % Of the polymerization was terminated. After adjusting the pH of the obtained copolymer latex to 8 using sodium hydroxide, unreacted monomers were removed by steam distillation to obtain a polymer latex A (solid content concentration: 48% by weight, viscosity: 120 CPS). The number average particle size was 165 nm and the gel content was 38%. Also, 1
It contained 0.288% by weight of giant particles of μm or more.

Polymer latex B: 1.2 parts of sodium dodecylbenzenesulfonate and 40 parts of 1,3-butadiene, 40 parts of styrene and methyl methacrylate 5
Part A, acrylonitrile 10 parts, β-hydroxyethyl acrylate 2 parts, a monomer mixture consisting of acrylic acid 3 parts, and t-dodecyl mercaptan 0.9 parts except that the polymer latex B was changed in the same manner as the polymer latex A.
(Solid content: 48% by weight, viscosity: 110 CPS).
The number average particle diameter was 100 nm, and the gel content was 68%.
Met. Further, it contained 0.336% by weight of giant particles of 1 μm or more.

Polymer latex C: 0.1 part of sodium dodecylbenzenesulfonate, 1,3-butadiene 40
Part of styrene, 58 parts of styrene and 2 parts of acrylic acid, 0.3 part of t-dodecyl mercaptan and polymer latex C (solids) in the same manner as polymer latex A except that the polymerization temperature was changed to 65 ° C. A concentration of 50% by weight and a viscosity of 320 CPS) were obtained. The number average particle diameter was 220 nm and the gel content was 91%. Also, 1μ
0.250% by weight of giant particles of m or more.

Polymer latex D: 100 parts of water, 0.15 part of sodium dodecylbenzenesulfonate, 0.3 part of sodium hydrogen carbonate in a 100 liter autoclave
Part, potassium persulfate 1.0 part and 1,3-butadiene 40 parts, styrene 51.5 parts and methyl methacrylate 5 parts, fumaric acid 2 parts, β-hydroxyethyl acrylate 0.5 part and acrylamide 1 part Mixture, t-dodecyl mercaptan 1.3 as chain transfer agent
Five parts were charged and polymerization was carried out at 60 ° C., and the polymerization was completed at a polymerization conversion of 97%. After adjusting the pH of the obtained copolymer latex to 8 using sodium hydroxide, unreacted monomers were removed by steam distillation to obtain a polymer latex D (solid content concentration: 48% by weight, viscosity: 110 CPS). The number average particle size was 180 nm, and the gel content was 15%. In addition, it contained 2.987% by weight of giant particles of 1 μm or more.

[Examples 1A to 4A, Comparative Examples 1B to 3B]
2 m3 of each of the polymer latexes A to D obtained above
Is a disk-shaped filter medium (area: 0.045 m2) made of stainless steel plain woven wire mesh with meshes of 75 μm: filter medium a, maximum pore diameter 5
Disc-shaped filter medium (area 0.045 m2) made of a sintered metal made of stainless steel fiber having a porosity of 78% and having a porosity of 78%: Filter medium b or disc-shaped filter medium made of an electronic sieve having openings of 10 μm ( Area: 0.045 m2) A filter device (New Log) that uses the filter medium c and can give a vibration (reciprocating motion) at a specific amplitude and a specific vibration frequency in the circumferential direction of the filter medium in the horizontal plane.
Filtration was performed under the pressures shown in Table 1 while applying the amplitudes and vibration frequencies shown in Table 1 using a “vibration type membrane separator“ V ☆ SEP ”manufactured by ic International). Then, polymer latex C2m3
1 kg of diatomaceous earth was added to the mixture, and the mixture was sufficiently stirred and then subjected to filtration. Filtration time, filtration speed (rate per filtration area of 0.045 m2), amount of latex purified by filtration, amount of macroparticles (% by weight) of 1 μm or more in latex purified by filtration, and 1 μm or more in filtration residue Table 1 shows the results of the amount of macroparticles (% by weight).

[0049]

[Table 1]

Examples 1A to 1 employing the filtration method of the present invention
4A could be filtered efficiently. In Comparative Example 1B, no filtration was performed because no pressure was applied, and in Comparative Example 2B, clogging occurred halfway due to the low frequency, and the filtration speed was also inferior. In Comparative Example 3B, since no vibration was applied to the filter medium, clogging occurred, and no filtration was possible.

[0051]

EFFECT OF THE INVENTION By employing the filtration method of the present invention, latex can be efficiently filtered, which is industrially useful.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 36/04 C08F 36/04 C08J 3/03 CEQ C08J 3/03 CEQ 3/075 CEQ // C08L 9:10 13:02

Claims (10)

[Claims] 1. A filter medium made of metal, reciprocating at an average speed of 20 cm / sec or more in a direction parallel to the surface of the filter medium, and under a pressure of 0.005 to 15 kg / cm 2 at a gauge pressure. A method for filtering latex, comprising filtering. 2. A reciprocating motion of an average speed of 20 cm / sec or more in a metal filter medium at an amplitude of 3 to 20 degrees and a vibration frequency of 10 to 120 Hz in a circumferential direction in a horizontal plane of the filter medium.
A method for filtering latex as described above. 3. The method for filtering latex according to claim 1, wherein the metal filter medium is a woven wire mesh having a mesh size of 1 to 150 μm. 4. The method for filtering latex according to claim 1, wherein the metal filter medium is a sintered metal body having a maximum pore size of 1 to 150 μm determined by a bubble point pressure measuring method. 5. The method for filtering latex according to claim 1, wherein the metal filter medium is an electric sieve having an opening of 1 to 150 μm. 6. The method for filtering latex according to claim 1, wherein the amount of macroparticles having a particle size of 1 μm or more in the filtration residue is 20% by weight or less. 7. The method for filtering latex according to claim 1, wherein a filter aid is used. 8. A latex comprising a conjugated diene monomer alone,
The method for filtering latex according to any one of claims 1 to 7, wherein the latex is composed of a monomer copolymerizable therewith. 9. The conjugated diene-based monomer according to claim 9, wherein the latex is
80% by weight, 0.5% of ethylenically unsaturated carboxylic acid monomer
To 10% by weight and a monomer copolymerizable therewith
9. The method for filtering latex according to claim 8, wherein a monomer comprising 89.5% by weight is emulsion-polymerized. 10. A paper coating binder comprising a latex purified by the filtration method according to claim 8.