JP3398509B2 - Seed dispersion for emulsion polymerization and latex dispersion using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a seed dispersion for emulsion polymerization and a latex dispersion obtained by emulsion polymerization in the presence of the seed dispersion. More specifically, it relates to a latex dispersion having a small amount of polymerization residue and a stable latex particle size and excellent adhesiveness.

[0002]

2. Description of the Related Art Conjugated diene latex has been used as a binder in applications such as coated paper, carpet backing, and water-based adhesives. However, it is desired to reduce the cost by increasing the adhesiveness of the binder and decreasing the binder ratio.

It is desirable that the polymer of the highly adhesive latex has a high molecular weight and low cross-linking. In order to control the cross-linking during the emulsion polymerization of the conjugated diene latex to reduce the cross-linking, there are a method of lowering the polymerization temperature and a method of increasing the monomer concentration in the polymer. However, lowering the polymerization temperature and increasing the concentration of the monomer during emulsion polymerization lead to the generation of a large amount of polymerization residue and the enlargement of the latex particle size, which is inconvenient for the polymerization stability.

The seed emulsion polymerization method is known as a method for stably carrying out the polymerization, and an example thereof is JP-A-2-235906.
Japanese Patent Application Laid-Open No. 3-182504 discloses a seed emulsion polymerization method using a crosslinked seed polymer dispersion. In this method, since the seed polymer is crosslinked, the seed particles do not fuse even when swollen by the monomer,
Polymerization can be stabilized. JP-A-63-189413 and JP-A-2-240108 show methods of emulsion polymerization with a low molecular weight seed polymer. Japanese Unexamined Patent Publication (Kokai) No. 5-32710 describes a seed emulsion polymerization method using a fine particle size seed. JP-A-6-24803
Japanese Patent Publication No. 0 describes that the proportion of carboxylic acid on the surface of the seed polymer is adjusted. However, these methods do not provide stability in low temperature polymerization to obtain highly adhesive latex and polymerization of high concentration monomer.

[0005]

DISCLOSURE OF THE INVENTION In the production of latex by the seed emulsion polymerization method, particularly in the production of conjugated diene latex, the present invention suppresses enlargement of latex particle size and generation of large amount of polymerization residue to stabilize polymerization. It is an object of the present invention to provide a seed dispersion and a latex dispersion using the seed, which can be used to obtain a latex with high solid content and high adhesion.

[0006]

DISCLOSURE OF THE INVENTION The present invention comprises 0.5 to 10 parts by weight of an ethylenic monocarboxylic acid alkyl ester monomer having a hydroxyl group, 0.5 to 10 parts by weight of an ethylenically unsaturated monocarboxylic acid or dicarboxylic acid, and The average particle diameter obtained by emulsion polymerization of 80 to 99 parts by weight of another ethylenically unsaturated monomer is 10 to 70 nm, and the relationship between the weight average molecular weight (Mw) of the polymer and the glass transition temperature (Tg) is
(1) 2 × 10 ⁴ <Mw <1 × 10 ⁶ , (2) −20 ° C. <Tg
<70 ° C, (3) Mw x Tg <2 x 10 ⁷ (however, Mw
Is a polystyrene-equivalent, Tg unit is ° C), which is a seed dispersion liquid for emulsion polymerization.

Further, the present invention is characterized in that the conjugated diene monomer, the aromatic vinyl monomer and the other ethylenically unsaturated monomer are emulsion-polymerized in the presence of the above emulsion polymerization seed dispersion. . Examples of the ethylenic monocarboxylic acid alkyl ester monomer having a hydroxyl group used in the emulsion dispersion seed dispersion of the present invention include, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
2-hydroxyethyl methacrylate etc. can be mentioned. One or two of these alkyl esters
More than one kind is used, and the total amount thereof is preferably 0.5 to 10 parts by weight, preferably 1 to 7 parts by weight, based on the whole seed polymer, because the seed dispersion and the latex dispersion using the same can be stably obtained. .

Examples of the ethylenically unsaturated monocarboxylic acid used in the emulsion dispersion of the present invention include acrylic acid, methacrylic acid and crotonic acid. Examples of the ethylenically unsaturated dicarboxylic acid include itaconic acid, fumaric acid, maleic acid and the like. Although one or more of these carboxylic acids may be used, it is preferably either a monocarboxylic acid or a dicarboxylic acid. The amount used of them is
0.5 to 10 parts by weight, preferably 1 to 7 parts by weight is preferable because a seed dispersion and a latex dispersion using the same can be stably obtained.

Other ethylenically unsaturated monomers used in the emulsion polymerization seed dispersion of the present invention include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, Ethyl carboxylic acid alkyl ester monomers such as ethyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene and p-methylstyrene, acrylonitrile, Vinyl cyanide monomers such as methacrylonitrile and α-chloroacrylonitrile, conjugated diene monomers such as 1,3-butadiene, isoprene and 2-chloro-1,3-butadiene, acrylamide, methacrylamide, N- Methylol acrylamide, N-methyl N-monoalkyl (meth) acrylamides such as acrylamide, N-methylmethacrylamide, N, N-dialkyl (meth) acrylamides such as N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, carboxylic acids such as vinyl acetate Examples thereof include halogenated unsaturated monomers such as vinyl esters, vinyl chloride and vinylidene chloride, and ethylenic amines such as aminoethyl acrylate and dimethylaminoethyl acrylate. These other ethylenically unsaturated monomers are used in combination of one or more, and used in an amount of 80 to 99 parts by weight based on the whole seed polymer.

The seed dispersion for emulsion polymerization of the present invention can be emulsion-polymerized by combining a plurality of unsaturated monomers. The weight ratio of these unsaturated monomers is such that the glass transition temperature (Tg) of the polymer after synthesis is higher than -20 ° C and 70 ° C.
Need to be lower. The polymer of the emulsion dispersion seed dispersion of the present invention has a weight average molecular weight (Mw) of 2 × 10 ⁴ to 1 × 10 ⁶ in terms of polystyrene, and Mw ×
It must be adjusted so that Tg is smaller than 2 × 10 ⁷ . The adjustment method is determined by the emulsion polymerization temperature during synthesis, the unsaturated monomer concentration, the amount of polymerization initiator, the amount of chain transfer agent, and the like.

When the polymer of the seed dispersion for emulsion polymerization of the present invention has specified Mw and Tg, the polymerization residue is remarkably reduced, and the target latex particle size is obtained. A big quality advantage is born. The emulsion dispersion seed dispersion of the present invention preferably has a polymer particle size of 10 to 70 nm. More preferably 20-
It is 50 nm. When the particle size is 10 to 70 nm, the amount used as a seed in emulsion polymerization is small,
It is preferable because it does not affect the performance of the latex polymer. The method of controlling the particle size is the emulsion polymerization temperature during synthesis,
The concentration of the initial emulsifier and the concentration of the initial polymerization initiator can be adjusted appropriately.

The seed dispersion for emulsion polymerization of the present invention can be synthesized by a general emulsion polymerization method. That is, it can be synthesized by emulsion polymerization in which an emulsifier, an unsaturated monomer, a chain transfer agent, a polymerization initiator and the like are added to an aqueous medium (usually ion-exchanged water or distilled water) and the mixture is heated and stirred. The emulsifier, unsaturated monomer, chain transfer agent and polymerization initiator may be added all at once, continuously and uniformly, or continuously and unevenly.

Examples of emulsifiers used in a general emulsion polymerization method include fatty acid soap, rosin acid soap,
Anionic surfactants such as alkyl sulfonates, dialkyl aryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulphates, polyoxyethylene alkyl aryl sulphates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers , Nonionic surfactants such as polyoxyethylene sorbitan fatty acid ester oxyethylene oxypropylene copolymer. These surfactants are usually anionic surfactants alone or anionic /
Used in a mixed system of nonionic surfactants.

As a chain transfer agent used in a general emulsion polymerization method, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan and t-dodecyl mercaptan, tetramethylthiuram disulfide. , Tetraethylthiuram disulfide and other disulfides, 2-ethylhexyl thioglycolate, α-methylstyrene dimer, cyclohexene and the like, and further a water-soluble chain transfer agent such as sodium phosphinate.
The chain transfer agent may be used without addition or in combination of one or more kinds.

A polymerization initiator used in a general emulsion polymerization method has a function of radically decomposing by the action of heat or a reducing agent to cause addition polymerization of a monomer. Examples include water-soluble or oil-soluble peroxodisulfates, peroxides, azobis compounds, and the like. Specifically, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t- Butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, cumene hydroperoxide, etc.
Particularly preferred is peroxodisulfate.

Examples of the reducing agent used in a general emulsion polymerization method include acidic sodium sulfite, ascorbic acid and salts thereof, erythorbic acid and salts thereof, rongalite and iron ions. By using one kind or two or more kinds of these reducing agents in combination with a polymerization initiator, so-called redox polymerization is made possible, and acceleration of the polymerization or polymerization at a lower temperature is made possible.

A polymerization modifier used as necessary in a general emulsion polymerization method can be used. For example, there are pH adjusting agents such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and disodium hydrogen phosphate, and chelating agents such as sodium ethylenediaminetetraacetate. The latex dispersion of the present invention is obtained by emulsion polymerization of unsaturated monomers in the presence of the seed dispersion for emulsion polymerization described above. Emulsion polymerization temperature is 20-8
0 ° C is preferred. More preferably, it is 30 to 70 ° C.
When the emulsion polymerization temperature is 20 to 80 ° C., the polymerization residue is remarkably reduced, and the target latex particle size is obtained, which is a great advantage in terms of latex production and quality.

Examples of the conjugated diene monomer used in the latex dispersion of the present invention include 1,3-butadiene, isoprene and 2-chloro-1,3-butadiene. These conjugated diene monomers may be used alone or in combination of two or more. The aromatic vinyl monomer used in the latex dispersion of the present invention is the same as the aromatic vinyl monomer shown in the seed dispersion for emulsion polymerization.

Other ethylenically unsaturated monomers used in the latex dispersion of the present invention include ethylenic monocarboxylic acid alkyl ester monomers and ethylenically unsaturated monocarboxylic monomers shown in the emulsion polymerization seed dispersion. It is the same as the other ethylenically unsaturated monomers excluding the acid, ethylenically unsaturated dicarboxylic acid and / or aromatic vinyl monomer. You may use these 1 type or in combination of 2 or more types.

The latex dispersion of the present invention can be produced by a general emulsion polymerization method except for the above points.

[0021]

Examples 1 to 8 <Synthesis of Emulsion Polymerization Seed Dispersion> 170 parts by weight of ion-exchanged water (hereinafter referred to as all parts) was preliminarily replaced with nitrogen in a temperature-adjustable reactor equipped with a stirrer. However,
(Except for ion-exchanged water, unsaturated monomer, and chain transfer agent, dry parts by weight) are charged with 10 parts of sodium dodecylbenzenesulfonate, 0.1 part of sodium hydroxide and the amount of sodium persulfate shown in Table 1 and stirred. While heating to 40 ° C. Then, a reducing agent system in which 0.5 parts of sodium bisulfite and 0.0005 parts of ferric nitrate were dissolved in 10 parts of ion-exchanged water after adding all the unsaturated monomer mixture and the chain transfer agent shown in Table 1 The aqueous solution was added all at once. Since the temperature in the polymerization system rises as soon as the reducing agent aqueous solution is added, 90 ° C
The temperature was adjusted to. After that, the temperature in the polymerization system was lowered by maintaining 90 ° C. for 2 hours to obtain a seed dispersion liquid for emulsion polymerization.
The synthesized emulsion polymerization seed dispersion liquid has a solid content of 40%, and the polymer particle size, Tg and Mw are shown in Table 1.

The particle size is a calculated value obtained by the glow-up method, T
g was measured with a differential scanning calorimeter (DSC), and the inflection point of the measurement chart was taken as Tg. Further, Mw was measured by GPC using tetrahydrofuran as a carrier liquid, and quantified by a polystyrene standard molecular weight reagent. <Production of latex dispersion> Next, 5 parts of the synthesized seed dispersion for emulsion polymerization and 0.5 part of sodium dodecylbenzenesulfonate were ion-exchanged in a pressure-added reactor having a stirrer with a temperature controllable atmosphere and nitrogen substitution. Charged after adding to 110 parts of water, 45 parts of styrene, 45 parts of butadiene, 2 parts of 2-hydroxyethyl acrylate, 3 parts of acrylic acid, t
-0.5 parts of dodecyl mercaptan was added to the pressure reactor and brought to 50 ° C. A polymerization initiator-based aqueous solution prepared by dissolving 0.35 part of sodium persulfate and 0.1 part of sodium hydroxide in 10 parts of ion-exchanged water was added all at once to a pressure reactor,
After holding for 6 hours, the mixture was further reacted at 80 ° C. for 3 hours and then cooled to prepare a latex dispersion liquid. The produced latex dispersion has a solid content of 44%, the latex particle size and the polymerization residue are shown in Table 1.

The latex particle size was measured using a light scattering particle size measuring device, and the polymerization residue was passed through the latex dispersion obtained through a 200-mesh sieve, and the dry weight of the agglomerates remaining on the sieve was taken as the latex. The value converted per liter was used.

[0024]

[Table 1]

Here, the symbols of the monomers shown in the table represent the substances shown below. NPS: sodium persulfate, St: styrene, MMA:
Methyl methacrylate, BA: Butyl acrylate, E
HA: 2-ethylhexyl acrylate, HEA: 2
-Hydroxyethyl acrylate, MAA: methacrylic acid, AA: acrylic acid, IA: itaconic acid, DDM: t
− Dodecyl mercaptan

[0026]

Example 9 A seed dispersion for emulsion polymerization was obtained in exactly the same manner as the synthesis method of the seed dispersion for emulsion polymerization of Example 1 except that 290 parts of initial ion-exchanged water and 16 parts of sodium dodecylbenzenesulfonate were used. It was The synthesized seed dispersion for emulsion polymerization had a solid content of 28% and a polymer particle size of 25 n.
m and Tg were 10 ° C., and Mw was 50 × 10 ⁴ .

A latex dispersion was obtained in the same manner as in the method for producing the latex dispersion of Example 1, except that 1.2 parts of the emulsion polymerization seed dispersion and 48.8 parts of styrene were used. The produced latex dispersion had a solid content of 44%, a latex particle size of 110 nm, and a polymerization residue of 0.07 g / l.
As is clear from Examples 1 to 9, when the amount is within the range specified by the present invention, the produced latex dispersion has a small amount of polymerization residue and the target latex particle size is obtained, which is excellent in production and quality. It turns out to be excellent.

[0028]

Comparative Examples 1 to 7 <Synthesis of Emulsion Polymerization Seed Dispersion> Except for sodium persulfate, unsaturated monomer, and chain transfer agent shown in Table 2, the emulsion polymerization seed dispersion was prepared in exactly the same manner as in Examples. Was synthesized. The synthesized emulsion polymerization seed dispersion liquid has a solid content of 40%, and the polymer particle size, Tg and Mw are shown in Table 2. <Production of Latex Dispersion> A latex dispersion was produced in exactly the same manner as in Example except that the seed dispersion for emulsion polymerization shown in Table 2 was used. The solid content, latex particle size and polymerization residue of the produced latex dispersion are shown in Table 2.

[0029]

[Table 2]

[0030]

Comparative Example 8 A latex dispersion was prepared in exactly the same manner as in Example, except that the seed dispersion for emulsion polymerization was not used and the initial amount of sodium dodecylbenzenesulfonate was 1.0 part. The latex dispersion produced had a solid content of 38.
%, Latex particle size is 135 nm, polymerization residue is 15.0
It was g / l.

As is apparent from Comparative Examples 1 to 8, when the amount is outside the range specified by the present invention, the latex dispersion produced had a large amount of polymerization residue and the target latex particle size could not be obtained. It can be seen that the quality and quality are inferior.

[0032]

INDUSTRIAL APPLICABILITY The present invention suppresses the enlargement of the latex particle size and the generation of a large amount of the polymerization residue in the production of latex by the seed emulsion polymerization method, particularly the production of conjugated diene latex, and the stable polymerization is achieved. It is possible to produce a seed dispersion that gives a highly adhesive latex with a solid content and a latex dispersion using the seed.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-6-248004 (JP, A) JP-A-5-32711 (JP, A) JP-A-3-167398 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (2)

(57) [Claims] 1. 0.5 to 10 parts by weight of an ethylenic monocarboxylic acid alkyl ester monomer having a hydroxyl group, 0.5 to 10 parts by weight of an ethylenically unsaturated mono- or dicarboxylic acid, and other ethylenically unsaturated monomer. The average particle size obtained by emulsion polymerization of 80 to 99 parts by weight of the body is 10 to 70 nm, and the relationship between the weight average molecular weight (Mw) of the polymer and the glass transition temperature (Tg) is (1) 2 × 10 ⁴ < Mw <1 x 1
^{0 6, (2) -20 ℃} <Tg <70 ℃, (3) Mw × Tg <
A seed dispersion for emulsion polymerization, wherein the seed dispersion is 2 × 10 ⁷ (wherein Mw is in terms of polystyrene, the unit of Tg is ° C). 2. A latex dispersion obtained by emulsion-polymerizing a conjugated diene monomer, an aromatic vinyl monomer and another ethylenically unsaturated monomer in the presence of the seed dispersion for emulsion polymerization according to claim 1. liquid.