JP2003201699A - Conjugated diene/aromatic vinyl-based copolymer latex for paper coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conjugated diene/aromatic vinyl-based copolymer latex more effectively producible than conventional ones, wherein the latex forms a coating composition for paper coating excellent in mechanical stability, and the coated paper obtained by coating and drying the coating composition has excellent coated paper properties such as dry pick strength, wet pick strength, blister resistance and excellent heat-discoloring resistance when the paper is printed. <P>SOLUTION: This copolymer latex for paper coating is obtained by polymerizing an aliphatic conjugated diene monomer with an aromatic vinyl monomer in the presence of ≤35 ppm total polymerization inhibitor in the monomers at ≤75°C. The copolymer latex has ≤15 h polymerization time corresponding to 95 wt.% polymerization conversion. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a copolymer latex for paper coating. Specifically, it can be produced more efficiently than conventionally known paper coating copolymer latex, and the mechanical stability of the paper coating composition obtained using the copolymer latex of the present invention is excellent, Furthermore, the coated paper obtained by coating and drying the coating composition for paper coating is excellent in coated paper properties such as dry pick strength, wet pick strength and blister resistance during printing, and has a heat discoloration resistance. The present invention relates to a conjugated diene-aromatic vinyl-based copolymer latex for paper coating, which is also excellent in performance.

[0002]

2. Description of the Related Art Coated paper is manufactured by coating a surface of a coated base paper with a coating composition for paper coating and drying. Generally, a coating composition for paper coating is clay, a pigment dispersion liquid in which inorganic or organic white pigments such as calcium carbonate and polystyrene are dispersed in water, a binder for adhering and fixing pigments or pigments to base paper, and other additives. Is a water-based paint.
As the binder, a synthetic emulsion binder typified by a styrene-butadiene copolymer latex and a natural binder typified by starch or casein are used. Among them, styrene-butadiene copolymer latex has a large degree of freedom in quality design, and is widely used today as a binder most suitable for a coating composition for paper coating. Is said to have a great influence on the performance of the coating composition for paper coating or on the quality such as dry pick strength during printing, wet pick strength, blister resistance, and heat discoloration performance required for the final coated paper product. ing.

Particularly in today's high-speed printing, coated papers are required to have higher levels of surface strength and blister resistance than ever before. Further, the printed matter is required to have higher quality than ever before, and in many cases, the heat discoloration resistance of the non-image area after printing is required.

While demands for the above performance have increased, in recent years low-cost coated papers and paper-making materials have been imported from overseas, and each manufacturer of coated papers aims to further reduce costs. Therefore, there is an urgent need to maintain and improve the quality of the above-mentioned coated paper while reducing the amount of the binder which is inexpensive and has a high adhesive strength as compared with the conventional amount used. Therefore, there is also a strong demand for a styrene-butadiene copolymer latex that has high productivity and can be produced at a lower cost than before, and that is excellent in the required quality.

In order to improve the adhesive strength of the copolymer latex, for example, a method of adjusting the gel content in the copolymer latex and a method of improving the composition of the copolymer have been proposed. The surface strength of coated paper and other required properties often conflict with each other, and it was not easy to improve all properties in a well-balanced manner.

Various techniques for improving the above-mentioned physical property balance have been disclosed, but they have not yet reached a sufficiently satisfactory level.
No. 172894 discloses a technique in which a copolymer latex having a specific molecular weight is polymerized at a relatively low temperature by using a specific two-stage polymerization method to exhibit good properties. When the polymerization is carried out in (1), it is difficult to obtain a copolymer latex having excellent cost performance because the reaction time becomes long and the productivity is lowered, and improvement has been strongly desired.

On the other hand, a latex obtained by copolymerizing a conjugated diene is considered to be more advantageous than other copolymer latexes such as acrylic latex in terms of strength of coated paper, but with respect to heat discoloration resistance. It is said to be relatively inferior, and improvement of the balance was also desired.

[0008]

The present invention can be produced more efficiently than the conventionally known copolymer latex for paper coating, and is a coating composition for paper coating obtained by using the copolymer latex of the present invention. The coated paper obtained by coating and drying the coating composition for paper coating has excellent mechanical stability, and has a dry pick strength during printing, wet pick strength, blister resistance, etc. It is an object of the present invention to provide a conjugated diene-aromatic vinyl-based copolymer latex for paper coating, which is excellent in paper-making properties and is also excellent in heat discoloration performance.

[0009]

Means for Solving the Problems The inventors of the present invention have made diligent studies to solve the current problems in view of the above circumstances, and as a result, have found that the polymerization inhibitor or stabilizer in the monomer used in the reaction is The inventors have devised such that the amount is not more than a certain amount, and have found that the above-mentioned problems can be solved by a copolymer latex obtained under specific conditions, and have completed the present invention.

That is, according to the present invention, (1) 25 to 70% by weight of an aliphatic conjugated diene monomer and 15 aromatic vinyl monomers are used.
~ 74 wt%, ethylenically unsaturated carboxylic acid monomer 1 ~
10% by weight and other monomers copolymerizable with them 0 to
A copolymer latex obtained by emulsion-polymerizing 100 parts by weight of a total of 59% by weight of monomers, wherein the aliphatic conjugated diene-based monomer part A used for emulsion polymerization of the copolymer latex is A. And the sum of aromatic vinyl monomer parts B (A +
The ratio (a + b) / (A + B) of the sum (a + b) of the polymerization inhibitor part a in the aliphatic conjugated diene monomer to the B) and the polymerization inhibitor part b in the aromatic vinyl monomer is 35 ppm.
A conjugated diene-aromatic vinyl copolymer latex for paper coating, characterized in that the reaction is carried out at a temperature of 75 ° C. or less, and (2) polymerization in an aliphatic conjugated diene monomer. After treating the amount of the inhibitor to 20 ppm or less, emulsion polymerization is started using the inhibitor, the conjugated diene-aromatic vinyl copolymer latex for paper coating according to (1), (3) in reaction system A reducing agent containing no iron is present in (1) or (2), the conjugated diene-aromatic vinyl copolymer latex for paper coating according to (1) or (2),
(4) The time from the addition of the polymerization initiator, which means the substantial start of the reaction, to the polymerization conversion rate of 95% by weight is within 15 hours, which is characterized in (1) to (3). It is intended to provide a conjugated diene-aromatic vinyl copolymer latex for paper coating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. Examples of the aromatic vinyl monomer in the present invention include styrene, α-methylstyrene, methyl α-methylstyrene, vinyltoluene and divinylbenzene, and these can be used alone or in combination of two or more. The use of styrene is particularly preferred. Presently, styrene used industrially contains about tens of ppm of tertiary butyl catechol as a polymerization inhibitor.

Examples of the aliphatic conjugated diene-based monomer used in the present invention include 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene,
Examples thereof include 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and these may be used alone or in combination of two or more. The use of 1,3-butadiene is particularly preferable. Currently, industrially used 1,3-butadiene also contains a polymerization inhibitor for the purpose of preventing polymerization during monomer storage,
The amount is more than several tens of ppm in the case of styrene, and generally, tertiary butyl catechol is approximately several tens of ppm to 10 ppm.
It is contained at 0 ppm.

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. Alternatively, two or more kinds can be used. In particular, acrylic acid, methacrylic acid, fumaric acid, and itaconic acid are preferably used.

Other monomers copolymerizable with the above monomers include unsaturated carboxylic acid alkyl ester monomers, unsaturated monomers containing a hydroxyalkyl group, vinyl cyanide monomers, Examples include saturated carboxylic acid amide monomers.

Examples of the unsaturated carboxylic acid alkyl ester monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl malate and dimethyl. Itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like can be mentioned, and one or more of these can be used. The use of methyl methacrylate is particularly preferable.

The unsaturated monomer containing a hydroxyalkyl group includes β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-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)
Examples thereof include maleate and 2-hydroxyethylmethyl fumarate, and these may be used alone or in combination of two or more. It is particularly preferable to use β-hydroxyethyl acrylate.

Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and α-ethylacrylonitrile.
These may be used alone or in combination of two or more. It is particularly preferable to use acrylonitrile or methacrylonitrile.

As the unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
Examples thereof include N-dimethylacrylamide, and these may be used alone or in combination of two or more. The use of acrylamide or methacrylamide is particularly preferred.

The above monomer composition comprises 25 to 70% by weight of aliphatic conjugated diene monomer and 15 to 15 aromatic vinyl monomer.
74% by weight, ethylenically unsaturated carboxylic acid monomer 1-1
0% by weight and other monomers copolymerizable with them 0-5
It is necessary to be 9% by weight.

If the aliphatic conjugated diene monomer is less than 25% by weight, the dry pick strength out of the surface strength required at the time of printing, and if it exceeds 70% by weight, the wet surface strength at the time of printing is required. The so-called wet pick strength is inferior, which is not preferable. Preferably 30-60% by weight,
More preferably, it is 35 to 55% by weight.

If the aromatic vinyl monomer content is less than 15% by weight, the wet pick strength required at the time of printing is more than 74% by weight, and the dry pick strength required at the time of printing is inferior. Preferably 20-65% by weight,
It is more preferably 25 to 60% by weight.

If the amount of the ethylenically unsaturated carboxylic acid monomer is less than 1% by weight, the mechanical stability of the copolymer latex itself and the paper coating composition may be poor, and if it exceeds 10% by weight, the latex content may be low. It is not preferable because the viscosity becomes high, which may cause a problem in handling the copolymer latex itself. More preferably, it is 1 to 8% by weight.

If the total amount of the other copolymerizable monomers exceeds 59% by weight, the dry pick strength is deteriorated, which is not preferable. It is preferably 0 to 50% by weight, more preferably 0 to 40% by weight.

The copolymer latex of the present invention is the sum (A of the aliphatic conjugated diene monomer part A and the aromatic vinyl monomer part B) used for emulsion polymerization of the copolymer latex.
+ B), the ratio (a + b) / (A + B) of the sum (a + b) of the polymerization inhibitor part a in the aliphatic conjugated diene monomer and the polymerization inhibitor part b in the aromatic vinyl monomer is 35 pp.
m or less and the reaction temperature is 75
The temperature is preferably set to not higher than 0.degree. C., more preferably 50 to 75.degree. Latex polymerized at a temperature within this range has a good balance between dry pick strength and blister resistance and has high production efficiency.
On the other hand, when the ratio of the polymerization inhibitor exceeds 35 ppm, the reaction rate decreases at a reaction temperature of 75 ° C. or less, and the production efficiency of the copolymer latex decreases. When the reaction temperature exceeds 75 ° C regardless of the ratio of the polymerization inhibitor, the production efficiency of the copolymer latex can be secured, but the dry pick strength and the blister resistance of the coated paper are deteriorated. Incidentally, these polymerization inhibitors are usually t-butylcatechol (TB
C) is used.

As the chain transfer agent which can be used for producing the copolymer latex of the present invention, n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan. Alkyl mercaptans such as, dimethylxanthogen disulfide, xanthogen compounds such as diisopropylxanthogendisulfide, terpinolene, and tetramethylthiuram disulfide, tetraethylthiuram disulfide, thiuram-based compounds such as tetramethylthiuram monosulfide,
Phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide, α-
Benzyloxystyrene, α-benzyloxyacrylonitrile, vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, and the like, These may be used alone or in combination of two or more. The amount of these chain transfer agents is not particularly limited, but is usually 0 to 5 parts by weight with respect to 100 parts by weight of the monomer.

In the present invention, it is also possible to use α-methylstyrene dimer as a chain transfer agent. α-Methylstyrene dimer includes 2,4-diphenyl-4-methyl-1-pentene, 2, and 3 as isomers.
4-diphenyl-4-methyl-2-pentene and 1,
There is 1,3-trimethyl-3-phenylindane,
As the α-methylstyrene dimer used in the present invention, the content of 2,4-diphenyl-4-methyl-1-pentene is preferably 60% by weight or more, and particularly preferably 80% by weight or more. Since α-methylstyrene dimer has a high boiling point and remains in the latex particles even after the production of the copolymer latex, the amount of the α-methylstyrene dimer used is 100 parts by weight of the monomer because of an environmental problem different from the object of the present invention. It is preferable that the amount is less than 2 parts by weight.

As the polymerization method in the present invention, any one-step polymerization, two-step polymerization, multi-step polymerization, seed polymerization, power feed polymerization method or the like may be adopted, but two-step polymerization and multi-step polymerization are particularly preferable. Further, the addition method of various components in the polymerization method of the present invention is not particularly limited,
Any of a batch addition method, a divided addition method, and a continuous addition method can be adopted. It seems that a multi-step polymerization method of two or more steps by a continuous addition method as shown in the examples described later is preferable, and a multi-step polymerization method of three or more steps is more preferable.

In emulsion polymerization, a conventional emulsifier,
A polymerization initiator, a reducing agent containing no transition metal, a hydrocarbon solvent, an electrolyte, a polymerization accelerator, a chelating agent and the like can be used.

As the emulsifier, anionic salts such as sulfuric acid ester salts of higher alcohols, alkylbenzene sulfonates, alkyldiphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, sulfuric acid ester salts of nonionic surfactants, etc. Surfactants or nonionic surfactants such as an alkyl ester type of polyethylene glycol, an alkylphenyl ether type, an alkyl ether type and the like can be mentioned, and one or more of these can be used.

Examples of the polymerization initiator include water-soluble polymerization initiators such as potassium persulfate, sodium persulfate and ammonium persulfate, cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide and diisopropylbenzene hydrol. An oil-soluble polymerization initiator such as peroxide or 1,1,3,3-tetramethylbutyl hydroperoxide can be used as appropriate. It is particularly preferable to use a water-soluble polymerization initiator of potassium persulfate or sodium persulfate, or cumene hydroperoxide.

Further, it is preferable to allow a reducing agent to be present together with the polymerization initiator in the reaction system because the reaction rate is promoted without degrading the performance. However, the use of a reducing agent containing a transition metal such as iron results in heat resistance of coated paper It is not preferable because the discoloration performance tends to decrease. Even if a reducing agent containing a transition metal is used, if the metal sealant is added to the latex, the heat-resistant discoloration performance of the coated paper is slightly improved, but in order to sufficiently exert the effect of the present invention (heat-resistant discoloration performance). It is desirable to avoid the use of reducing agents containing transition metals such as ferrous sulfate as much as possible.
Specific examples of the reducing agent preferably used in the present invention include sulfite, bisulfite, pyrosulfite, nithionate, nithionate, thiosulfate, formaldehyde sulfonate, and benzaldehyde sulfonate. The reducing sulfonic acid salts thereof, carboxylic acids such as L-ascorbic acid, tartaric acid and citric acid, reducing sugars such as dextrose and sucrose, and amines such as dimethylaniline and triethanolamine. Particularly, sodium sulfite, sodium formaldehyde sulfonate, and L-ascorbic acid are preferable.

In the polymerization, saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane and cycloheptane, pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like. Hydrocarbon compounds such as saturated hydrocarbons, aromatic hydrocarbons such as benzene, toluene and xylene may be used. In particular, cyclohexene and toluene, which have an appropriately low boiling point and are easily recovered and reused by steam distillation after the completion of the polymerization, are preferable from the viewpoint of environmental problems, although they are different from the object of the present invention.

Further, the copolymer latex produced in the present invention is used as a coating composition for paper coating together with a pigment. Examples of such pigments include inorganic pigments such as kaolin clay, talc, barium sulfate, titanium oxide, calcium carbonate, aluminum hydroxide, zinc oxide, and satin white, or organic pigments such as polystyrene latex and binder pigment. These may be used alone or in combination.

If desired, modified starch such as starch, oxidized starch, esterified starch, natural binder such as soybean protein and casein, or water-soluble synthetic binder such as polyvinyl alcohol may be used. Further, synthetic latex such as polyvinyl acetate latex and acrylic latex may be used in combination with the copolymer latex of the present invention. It is desirable to control the solid content of the polymer latex to be less than 50% by weight.
Furthermore, it is desirable to control it to less than 20% by weight, and it is most desirable to use the copolymer latex of the present invention alone.

In preparing a coating composition for paper coating using the copolymer latex of the present invention, further other auxiliaries,
For example, dispersant (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, etc.), antifoaming agent (polyglycol, fatty acid ester, phosphate ester, silicone oil, etc.), leveling agent (funnel oil, dicyandiamide, urea, etc.), Preservatives, mold release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color water retention improvers (carboxymethyl cellulose, sodium alginate, etc.) may be added as necessary.

Further, as a method for coating the coating composition for paper coating on the base paper for coating, any known technique such as an air knife coater, a blade coater, a roll coater or a bar coater can be used. It doesn't matter.
After coating, the surface is dried and finished by calendering.

[0037]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples, parts and percentages are by weight unless otherwise specified. The evaluation of various physical properties in the examples was based on the following methods.

[0038]Evaluation of mechanical stability of paint Adjust the solid concentration of the paper coating composition to 30% by weight,
Type mechanical stability tester (Padder Stability Test
The mechanical roll between the metal roll and the rubber roll.
Until the solidified material is generated on the rubber roll.
The interval was measured and evaluated according to the following four grades. ◎ ... 45 minutes or more (very good) ○: 30 minutes or more and less than 45 minutes (good) △: 20 minutes to less than 30 minutes (somewhat bad) ×: less than 20 minutes (very bad)

[0039]Evaluation of dry pick strength of coated paper Tack value with relatively large division resistance using RI printer
Each coated paper sample was printed at the same time with 18 inks.
Grade 5 (best)
It was relatively evaluated from 1 to 1 (worst). 6 times stamp
A printing test was conducted and an average value was obtained.

[0040]Evaluation of wet pick strength of coated paper Each coated paper sample by Molton roll using RI printer
The dampening water is applied simultaneously to, and immediately after that, the division resistance
Is an ink with a medium tack value of 12 and each coated paper sample is the same.
Sometimes it is printed and the degree of picking at that time is judged with the naked eye
However, 5th grade (best) to 1st grade (worst)
Evaluated to. A printing test was conducted 6 times, and an average value was obtained.

[0041]Evaluation of blister generation temperature The coated paper sample printed on both sides was placed in an atmosphere of 20 ° C and 65% relative humidity.
Oil whose temperature can be adjusted by controlling the humidity for about one day in the atmosphere
Throw it into the bath and find the lowest temperature at which blister occurs.
I have The higher the temperature, the better the blister resistance.

[0042]Evaluation of heat discoloration resistance Hang each coated paper sample in a commercially available gear oven and
Heat treatment is carried out at 0 ° C. for 10 hours to obtain a sample for measuring yellowness. Hunter
According to JIS P-8123 using a whiteness tester
Standard magnesium oxide on the surface of each sample to measure yellowness
The relative reflectance of the blue, amber and green
Measure for each filter and get for each filter
The specific reflectances obtained are B (blue), A (amber),
G (green). The yellowness Y of each sample is Y = (A-
B) / G. The smaller the value of yellowness Y is
Excellent heat discoloration resistance.

[0043]Particle size measurement of copolymer latex The number average particle diameter was measured by the dynamic light scattering method. When measuring
Then use LPA-3000 / 3100 manufactured by Otsuka Electronics
did.

[0044]Measurement of gel content of copolymer latex Create a latex film in a room temperature atmosphere. afterwards
Weigh about 1g of latex film, 400cc
It is put in toluene and expanded and dissolved for 48 hours. Then this
It was filtered through a 300 mesh wire mesh and captured by the wire mesh.
The toluene-insoluble part was dried and weighed.
The gel content is defined as the percentage of the weight of the Tex film.
It was calculated by weight%.

[0045]T present in butadiene and styrene
-Method for quantifying butylcatechol (TBC) An aliquot of the sample was evaporated to dryness and the residue was diluted with 1N NaOH.
Dissolve. This solution was measured with a spectrophotometer at a wavelength of 540n.
Measure the absorbance at m. Tested from known amount of TBC
The TBC content of the sample was quantified from the calibration curve.

[0046]Measurement of polymerization conversion rate 15 hours after the start of reaction
Method Accurately weigh about 1.0 g of latex sample and
After drying in an oven for 60 minutes, measure the residual amount and
The total polymerization conversion rate was calculated by calculation.

[0047]

[Equation 1]

[0048]

[Equation 2]

[0049]Reduction of TBC contained in butadiene TBC is removed by contacting with 1N-NaOH.
TBC-free butadiene obtained by this operation
And the known proportion of TBC to butadiene
Determine the amount of TBC present in the ene.

[0050]Measurement of TBC contained in butadiene The amount of TBC contained in commercially available butadiene A was determined by the method described above.
It was 55 ppm when measured by. It was mentioned above
Butadiene C was obtained by a TBC weight reduction operation. Piggy
When the amount of TBC contained in EN C was measured by the above method,
It was 0 ppm. Butadiene A and butadiene C
Butadiene B was obtained by mixing at a ratio of 1/2. Butajie
The amount of TBC contained in B was measured by the method described above.
It was 18 ppm.

[0051]Measurement of TBC contained in styrene The amount of TBC contained in styrene A manufactured by Company A was determined by the method described above.
It was 35 ppm when measured by. B made by company B
The amount of TBC contained in B was measured by the method described above.
It was 13 ppm.

[0052]Method for producing copolymer latex (Example 1)
~ 7 and Comparative Examples 1 to 4) (Example 1) A pressure-resistant polymerization reactor was charged under a nitrogen atmosphere with pure water.
120 parts of water, dodecylbenzene sulfonic acid as an emulsifier
0.5 part of sodium, each monomer in the first step shown in Table 1 and
And α-methylstyrene dimer 0.5 part, L-ascor
After adding 0.3 part of bic acid and stirring thoroughly, potassium persulfate was added.
0.8 part of a glass was charged and the polymerization was started at 61 ° C. Start
After 5 hours, the polymerization temperature was raised to and maintained at 65 ° C.
Second-stage monomers and t-dodecyl mercaptan
0.2 parts, cyclohexene 5 parts, Perex SSL0.
5 parts, sodium formaldehyde sulfonate 0.05
Parts, and 10 parts of pure water were continuously added over 6 hours.
After maintaining the polymerization temperature at 65 ° C for 4 hours, stop the polymerization.
Diethylhydroxyamine was added as an agent to terminate the polymerization.
Finished. The polymerization conversion rate at this time was 97%. Next
Then, adjust the pH of the copolymer latex with caustic soda aqueous solution to about
After adjusting to 7, unreacted monomer and
Other low boiling compounds are removed to obtain copolymer latex.
It was

(Example 2) In a pressure-resistant polymerization reactor, 120 parts of pure water under a nitrogen atmosphere, 1.2 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1 and After 8 parts of cyclohexene and 0.2 part of n-octyl mercaptan were added and sufficiently stirred, 0.3 part of sodium persulfate was charged and polymerization was started at 64 ° C. After 4 hours from the start, the polymerization temperature was raised to and maintained at 66 ° C.
Each of the second stage monomers shown in Figure 2 and sodium persulfate 0.2
Parts, 0.2 parts of sodium bisulfite and 0.1 parts of n-octyl mercaptan were continuously added over 4 hours. Further, the polymerization temperature was raised to 68 ° C. and maintained, and each monomer in the third stage shown in Table 1, 0.3 parts of sodium persulfate, and 0.1 parts of sodium formaldehyde sulfonate were continuously added over 3 hours. Polymerization temperature as it is 68
After keeping the temperature at 4 ° C for 4 hours, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 98%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Example 3) In a pressure-resistant polymerization reactor, 105 parts of pure water under a nitrogen atmosphere, and Perex SSL as an emulsifier.
1.3 parts, sodium dodecylbenzene sulfonate 0.
After adding 2 parts, each monomer in the first stage shown in Table 1 and 4 parts of cyclohexene and 0.4 part of t-dodecyl mercaptan and stirring sufficiently, 1 part of potassium persulfate was charged and polymerization was started at 62 ° C. did. Four hours after the start, each monomer in the second stage shown in Table 1 and 0.3 part of potassium persulfate, 0.1 part of t-dodecyl mercaptan, Perex SSL, pure water 10
Parts were added continuously over 7 hours. Further, the polymerization temperature was raised to and maintained at 68 ° C., and each monomer in the third stage shown in Table 1, 0.2 parts of Perex SSL and 5 parts of pure water were continuously added over 1 hour. As it is, the polymerization temperature is 68 ° C.
After maintaining for 3 hours, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 96%. Then, after adjusting the pH of the copolymer latex to about 7 with an aqueous solution of sodium hydroxide, unreacted monomers and other low boiling point compounds are removed by steam distillation,
A copolymer latex was obtained.

Example 4 In a pressure-resistant polymerization reactor, 150 parts of pure water under a nitrogen atmosphere, Perex SS as an emulsifier were used.
L 0.1 part, sodium dodecylbenzenesulfonate 0.2 part, each monomer in the first stage shown in Table 1 and α-methylstyrene dimer 1 part, and t-dodecyl mercaptan 0.2 part were added and sufficiently stirred. Then, potassium persulfate 0.
5 parts and 0.2 part of L-ascorbic acid were charged and the polymerization was started at 62 ° C. Three hours after the start, each of the second stage monomers shown in Table 1 and 0.2 part of sodium persulfate, 0.2 part of L-ascorbic acid, and .alpha.-methylstyrene dimer of 0.2.
5 parts, 0.3 part of t-dodecyl mercaptan, 0.3 part of Perex SSL, 0.1 part of sodium dodecylbenzenesulfonate and 10 parts of pure water were continuously added over 4 hours. Furthermore, each monomer in the third step shown in Table 1, 0.1 part of sodium persulfate, and 0.1 part of L-ascorbic acid.
Parts, Perex SSL 0.2 parts, and pure water 5 parts were continuously added over 4 hours. The polymerization temperature was maintained as it was at 62 ° C. for 4 hours, and diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 97%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Example 5) In a pressure-resistant polymerization reactor, 130 parts of pure water under a nitrogen atmosphere, 1.2 parts of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1 and After adding 5 parts of cyclohexene and 0.1 part of t-dodecyl mercaptan and thoroughly stirring, 0.4 parts of potassium persulfate and 0.3 part of L-ascorbic acid were charged,
Polymerization was initiated at 70 ° C. Four hours after the start, each monomer in the second stage shown in Table 1 and sodium persulfate 0.3
Parts, sodium bisulfite 0.05 parts, cyclohexene 5 parts, t-dodecyl mercaptan 0.1 parts, Perex SSL 0.5 parts, and pure water 5 parts were continuously added over 3 hours. The polymerization temperature was raised to and maintained at 72 ° C., and each monomer in the third stage shown in Table 1 and 0.2 parts of sodium persulfate, 0.05 part of sodium sulfite, and Perex SSL0.1.
Parts, and 5 parts of pure water were continuously added over 2 hours. Further, the polymerization temperature was raised to 75 ° C. and maintained for 3 hours, and then diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 99%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

Example 6 In a pressure-resistant polymerization reactor, 115 parts of pure water in a nitrogen atmosphere, Perex SS as an emulsifier were used.
After adding 0.5 parts of L, 0.5 parts of each monomer in the first stage shown in Table 1 and 0.5 part of α-methylstyrene dimer, 0.2 parts of t-dodecyl mercaptan, 2.0 parts of cyclohexene and thoroughly stirring, 1.5 parts of potassium persulfate was charged and the polymerization was started at 65 ° C. Four hours after the start, each monomer in the second stage shown in Table 1 and 0.1 part of sodium persulfate, 0.1 part of sodium formaldehyde sulfonate, 0.2 part of α-methylstyrene dimer, t-dodecyl mercaptan. 0.4 parts, 4 parts cyclohexene, Perex SSL0.
2 parts and 10 parts of pure water were continuously added over 4 hours. Furthermore, each monomer in the third step shown in Table 1, 0.2 part of t-dodecyl mercaptan, and 0.1 parts of sodium persulfate.
Parts, sodium formaldehyde sulfonate 0.1 parts,
0.2 parts of Perex SSL and 10 parts of pure water were continuously added over 4 hours. As it is, the polymerization temperature is raised to 65 ° C.
After keeping the time, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 97%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

Example 7 In a pressure-resistant polymerization reactor, 95 parts of pure water under a nitrogen atmosphere, 0.5 part of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1 and After adding 0.5 parts of α-methylstyrene dimer and 4.0 parts of cyclohexene and thoroughly stirring, 0.7 parts of potassium persulfate and 0.03 part of ferrous sulfate heptahydrate were charged, and polymerization was carried out at 62 ° C. Started. After 3 hours from the start, the polymerization temperature was raised to and maintained at 65 ° C., and each monomer in the second stage shown in Table 1 and 0.2 part of sodium persulfate, 0.01 part of ferrous sulfate heptahydrate, t -0.1 parts of dodecyl mercaptan, 0.2 parts of sodium dodecylbenzene sulfonate, 1 pure water
0 part was added continuously over 6 hours. Furthermore, 0.2 parts of each monomer and α-methylstyrene dimer in the third stage shown in Table 1, 0.1 part of t-dodecyl mercaptan,
Sodium persulfate 0.2 parts, ferrous sulfate heptahydrate 0.01
Part, 0.1 part of sodium dodecylbenzene sulfonate,
5 parts of pure water was continuously added over 1.5 hours. After that, the polymerization temperature was kept at 65 ° C. for 4.5 hours, and then diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 98%.
Next, the copolymer latex was adjusted to pH with an aqueous solution of caustic soda.
Was adjusted to about 7 and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Comparative Example 1) In a pressure-resistant polymerization reactor, 120 parts of pure water under a nitrogen atmosphere, and Perex SS as an emulsifier.
L 0.3 parts, sodium dodecylbenzene sulfonate 0.1 part, first stage monomers shown in Table 1 and α-methylstyrene dimer 0.2 part, t-dodecyl mercaptan 0.3 part were added sufficiently. After stirring, 0.4 part of potassium persulfate was charged, and polymerization was started at 61 ° C. Four hours after the start, each monomer in the second step shown in Table 1, 0.2 parts of sodium persulfate, and 0.1 of α-methylstyrene dimer were used.
Parts, t-dodecyl mercaptan 0.1 part, cyclohexene 4 parts, sodium dodecylbenzene sulfonate 0.2
Parts, and 3 parts of pure water were continuously added over 3 hours. Further, each monomer in the third stage shown in Table 1 and 1 part of α-methylstyrene dimer, 0.1 part of t-dodecyl mercaptan.
Parts, 6 parts of cyclohexene, and 7 parts of pure water were continuously added over 4 hours. The polymerization temperature was maintained as it was at 61 ° C. for 4 hours, and diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 92.
%Met. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Comparative Example 2) In a pressure-resistant polymerization reactor, 98 parts of pure water in a nitrogen atmosphere, 0.8 part of sodium dodecylbenzenesulfonate as an emulsifier, each monomer in the first stage shown in Table 1 and 0.5 parts of α-methylstyrene dimer, t
-Dodecyl mercaptan (0.1 part) was added and sufficiently stirred, and then 1.0 part of potassium persulfate was charged and polymerization was started at 68 ° C. Three hours after the start, each monomer in the second stage shown in Table 1, 0.1 part of t-dodecyl mercaptan, and 3 parts of pure water were continuously added over 6 hours. Furthermore, each monomer in the third step shown in Table 1 and 4 parts of pure water were continuously added over 2 hours. After maintaining the polymerization temperature at 68 ° C. for 4 hours as it was, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 98%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Comparative Example 3) In a pressure-resistant polymerization reactor, 104 parts of pure water under a nitrogen atmosphere, and Perex SS as an emulsifier.
L 1.0 parts, first-stage monomers shown in Table 1, 0.2 parts of n-octyl mercaptan, and 8 parts of cyclohexene were added and sufficiently stirred, and then 0.8 parts of potassium persulfate and sodium formaldehyde sulfonate were added. Charge 0.2 parts, 6
Polymerization was started at 8 ° C. After 3 hours from the start, each monomer in the second step shown in Table 1 and 0.1 part of sodium persulfate,
0.2 part of n-octyl mercaptan, 0.1 part of sodium dodecylbenzenesulfonate and 6 parts of pure water were continuously added over 6 hours. Furthermore, each monomer in the third stage shown in Table 1, 0.1 part of sodium persulfate, 0.2 part of sodium formaldehyde sulfonate, and 5 parts of pure water were continuously added over 2 hours. The polymerization temperature is 6 as it is.
After maintaining at 8 ° C. for 4 hours, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 97%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

(Comparative Example 4) In a pressure-resistant polymerization reactor, 95 parts of pure water under a nitrogen atmosphere, and Perex SSL as an emulsifier.
0.3 part, sodium dodecylbenzene sulfonate 0.3.
3 parts, 1.5 parts of each monomer in the first step shown in Table 1 and α-methylstyrene dimer 1.5 parts were added and sufficiently stirred, and then 1 part of potassium persulfate and 0.2 part of L-ascorbic acid were charged, Polymerization was started at 80 ° C. Three hours after the start, each monomer in the second step shown in Table 1, 0.1 part of sodium L-ascorbate, and 0.1 part of t-dodecyl mercaptan.
Part, 0.2 part of sodium dodecylbenzene sulfonate,
10 parts of pure water was continuously added over 6 hours. Further, each monomer in the third stage shown in Table 1, 0.1 part of t-dodecyl mercaptan, 0.1 part of sodium dodecylbenzenesulfonate and 5 parts of pure water were continuously added over 1.5 hours. Then raise the polymerization temperature to 85 ℃ and keep it
After maintaining for 4.5 hours, diethylhydroxyamine was added as a polymerization terminator to terminate the polymerization. The polymerization conversion rate at this time was 99.5%. Next, the pH of the copolymer latex was adjusted to about 7 with a caustic soda aqueous solution, and then unreacted monomers and other low boiling point compounds were removed by steam distillation to obtain a copolymer latex.

[0063]Preparation of paper coating composition The composition for paper coating having the following composition has a solid content of 63
It was created to be%. Kaolin clay 70 copies 30 parts calcium carbonate Sodium hydroxide 0.15 parts 4 parts starch 10 parts of copolymer latex

[0064]Preparation of single-side coated paper Using a commercially available hot air coating dryer MLC-100S type, coating
Composition for paper coating prepared on engineering base paper (basis weight 54 g / m2)
Coating amount of the liquid is 13 g / m2 using wire bars # 3-6.
The coating is performed so that 0.5 seconds after the coating,
In a drying oven, hot air with a temperature of 190 ° C and a wind speed of 36 m / sec
It was prepared by drying for 5 seconds.

[0065]Preparation of double-sided coated paper Double-sided coating was performed under the same conditions as for single-sided coated paper.

Each coated paper obtained was conditioned at a relative humidity of 65% and a temperature of 20 ° C. for a day and night, and then a linear pressure of 40 kg / c.
m, a temperature of 50 ° C., a sheet passing speed of 7 m / min, and four times of sheet passing, and super-calendering was performed. The results of the physical property test are shown in Table 1.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

As described above, the copolymer latex obtained by the present invention can be produced more efficiently than the conventionally known copolymer latex for paper coating, and can be obtained by using the copolymer latex of the present invention. For paper coating, which has excellent mechanical stability of the coating composition for paper coating, and the resulting coated paper has excellent dry pick strength during printing, wet topic strength, blister resistance, and heat yellowing resistance. A copolymer latex can be provided.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 220/02 C08F 220/02 222/00 222/00 236/04 236/04 (72) Inventor Wataru Fujiwara 2-10-2 Kikumoto-cho, Niihama-shi, Ehime Nihon A & L Co., Ltd. F-term (reference) 4J011 KA04 KA15 KB02 KB07 KB14 KB22 KB29 4J015 CA03 CA05 CA07 4J100 AB02Q AB03Q AB04Q AB16Q AJ01R AJ02R AJ08R AJ09S AL34S AL34S AL04S AL04S AL04S AL04S AM02S AM03S AM15S AM19S AM21S AS01P AS02P AS03P AS07P BA03S BB01S CA05 CA06 EA07 FA08 FA20 FA28 JA13 4L055 AG11 AG12 AG27 AG47 AG63 AG70 AG71 AG72 AG74 AG75 AG76 AG89 AH02 AH37 AJ04 BE02 BE08 EA20 EA32 FA11 FA12 FA13 FA19 FA22 FA30 GA19

Claims (4)

[Claims] 1. An aliphatic conjugated diene-based monomer 25 to 70% by weight, an aromatic vinyl-based monomer 15 to 74% by weight, an ethylenically unsaturated carboxylic acid monomer 1 to 10% by weight, and a combination thereof. A copolymer latex obtained by emulsion polymerization of a total of 100 parts by weight of a monomer composed of 0 to 59% by weight of another polymerizable monomer, which is used for emulsion polymerization of the copolymer latex. Polymerization in the aliphatic conjugated diene-based monomer A and the polymerization in the aromatic vinyl monomer relative to the sum (A + B) of the aliphatic conjugated diene-based monomer A and the aromatic vinyl monomer B Ratio (a
+ B) / (A + B) is 35 ppm or less, and 75
A conjugated diene-aromatic vinyl copolymer latex for paper coating, which is characterized in that the reaction is carried out at a temperature of ℃ or less. 2. The conjugated diene-aromatic vinyl copolymer copolymer for paper coating according to claim 1, wherein the aliphatic conjugated diene monomer treated so that the amount of the polymerization inhibitor is 20 ppm or less is used. Combined latex. 3. The conjugated diene-aromatic vinyl copolymer latex for paper coating according to claim 1, wherein a reducing agent containing no iron is present in the reaction system. 4. The time from the addition of the polymerization initiator, which means the substantial initiation of the reaction, to the polymerization conversion rate of 95% by weight is within 15 hours. The conjugated diene-aromatic vinyl copolymer latex for paper coating described.