JP2001079380A - Dispersant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersant having dispersibility and dispersion stability. SOLUTION: The dispersant that exhibits dispersing effect and the effect capable of suppressing the formation of a rigid precipitate layer when a slurry is kept without stirring is obtained by using the combination of a polycarboxylic acid copolymer having carboxyl groups and polyalkylene oxide structure on side chains and a vinyl alcohol copolymer having hydroxy groups, carboxyl groups and polyalkylene oxide groups on side chains. The dispersant is suitable for dispersing various powders, especially inorganic powders.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dispersant. More specifically, the present invention relates to a dispersant used for paints, inks, abrasives, ceramics, etc., and particularly preferably used for inorganic powders.

[0002]

2. Description of the Related Art In paints and inks, it is necessary to highly disperse inorganic pigments in a medium in order to maximize characteristics such as hiding power and coloring power of the inorganic pigments. Even in the case of an abrasive, it is necessary to highly disperse the abrasive powder so as not to form a hard agglomerated structure in order to realize higher-precision abrasiveness. Further, in ceramics molding, in order to obtain a molded body with more stable quality, it is necessary to highly disperse the raw material powder so that the ceramic powder as the raw material and various compounds are always in a uniform mixture. For dispersing these inorganic powders, dispersants such as sulfonic acid dispersants such as lignin and naphthalene, and polycarboxylate dispersants such as acrylic acid and maleic acid are used. But,
Even with inorganic powder slurries to which these dispersants are added, long-term dispersion stability is not always sufficient.

Therefore, it has been recognized that a carboxylic acid polymer having a polyalkylene glycol structure in the side chain is highly effective as a dispersant having both dispersibility and long-term dispersion stability (Japanese Patent Application Laid-Open No. 9-1990). -52921, JP-A-10-219180). However, even when using the polymers described in these examples, there is a problem that the aggregation of the particles proceeds during the long-term storage of the slurry while standing, forming a hard cake and making it difficult to redisperse. There is a need for a dispersant that suppresses the formation of hard cake and has excellent hard cake resistance.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves this problem, and is a dispersant which has excellent long-term dispersion stability, particularly excellent dispersibility of inorganic powder, and has excellent hard cake resistance and hard to form a hard cake. Is provided.

[0005]

As a dispersant for achieving the above object, a polycarboxylic acid copolymer having a carboxyl group and a polyalkylene oxide structure in a side chain and a hydroxyl group, a carboxyl group and a polyalkylene oxide structure in a side chain are used. When used in combination with a vinyl alcohol-based copolymer having the above, excellent dispersibility with respect to inorganic powder, long-term dispersion stability and hard cake resistance are obtained, and the effect of combining the above two copolymers is obtained. Is very prominent.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Examples of the polycarboxylic acid copolymer having a carboxyl group and a polyalkylene oxide structure in a side chain include those described in JP-A-6-256554, JP-B-6-88818, JP-B-6-88817, and the like. Esterified products of copolymers of unsaturated vinyl monomers and unsaturated dicarboxylic acids such as vinyl ether-maleic anhydride copolymer, olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, etc. with alkylene glycol-based compounds There is.

(Meth) acrylic acid esters as unsaturated groups described in JP-A-8-12396, JP-A-62-216950, JP-A-1-226575, JP-A-6-206750 and the like. There is a copolymer of a polyalkylene glycol derivative having a group, an unsaturated monocarboxylic acid or an unsaturated dicarboxylic acid, and a monomer having a sulfonic acid group such as allylsulfonic acid and methallylsulfonic acid.

Further, a monomer comprising a polyoxyalkylene derivative described in JP-A-7-53249, JP-A-7-215746, JP-A-8-165157, JP-A-7-232945 and the like, There is a copolymer containing a monomer containing a carboxyl group as an essential component.

Among them, a copolymer of polyalkylene glycol alkenyl ether represented by the general formula (1) and maleic anhydride, or a hydrolyzate thereof and / or
Alternatively, a salt of a hydrolyzate (hereinafter, referred to as “copolymer A”) is suitably used. In particular, those in which R ¹ is a vinyl group are most preferably used.

R ² can be appropriately selected depending on the type of the dispersion medium, the type of the inorganic powder, and the like. When used in an aqueous dispersion medium, R ² has an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group,
A tetrahydrofurfuryl group or hydrogen is preferred.

[0011]

Embedded image

(R ¹ is a vinyl group, an allyl group, AO is an oxyalkyl group having 2 to 4 carbon atoms, n is an integer of 1 to 200,
R ² is hydrogen or an organic residue such as an alkyl group having 1 to 20 carbon atoms, a phenyl group, a cyclohexyl group, or a tetrahydrofurfuryloxy group)

The salts of the hydrolyzate include salts with organic amines such as ammonium salts, triethylamine and triisopropanolamine, salts with divalent or higher metals such as calcium and aluminum, and salts with alkali metals such as sodium and potassium. Salt.

The molecular weight of the copolymer A is not particularly limited, but the weight average molecular weight measured by GPC is preferably from 5,000 to 200,000 in terms of polyethylene glycol.

The number of moles n of the alkylene oxide group added to the polyalkylene glycol alkenyl ether used in the copolymer A is preferably in the range of 1 to 200, more preferably in the range of 30 to 150. When the number of moles of the alkylene oxide group added is within the above range, the inorganic powder is favorably dispersed over a long period of time, and the effect of suppressing the generation of cake is produced.

As the method for producing the copolymer A, known polymerization means and polymer reaction means can be arbitrarily applied (for example, JP-A-9-52921 and JP-A-10-219180). The copolymer of the present invention is obtained by polymerization in a solvent and polymerization without a solvent. As the solvent used in the present invention, benzene, toluene, benzene derivatives such as ethylbenzene,
Examples thereof include ketones such as ethyl acetate and isopropyl acetate, and organic halides such as carbon tetrachloride and chloroform, and benzene derivatives are preferred in consideration of solvent removal, polymerization rate, and the like. The production method includes, for example, solution polymerization in which a radical catalyst such as benzoyl peroxide and azobisisobutyronitrile is used, and radical copolymerization is performed at 50 to 150 ° C. in a solvent. After dissolving maleic anhydride in alkylene glycol alkenyl ether, 50 to 50
This is a production method in which bulk polymerization is performed at 150 ° C.

The vinyl alcohol copolymer having a hydroxyl group, a carboxyl group and a polyalkylene oxide structure in the side chain of the present invention includes, for example, an unsaturated monomer having an alkylene oxide group described in JP-B-5-49683. There is a vinyl alcohol copolymer obtained by saponifying a copolymer of at least one of the above and vinyl acetate.

In Japanese Patent Application Laid-Open No. 4-114004, vinyl acetate and polyoxyethylene alkyl allyl phenyl ether or polyoxyethylene alkyl allyl oxy phenyl ether or polyoxyethylene alkyl allyl phenyl ether as unsaturated monomers are used. There is a vinyl alcohol-based copolymer obtained by saponifying the copolymer.

Among them, a vinyl alcohol copolymer obtained by saponifying a copolymer of a polyalkylene glycol alkenyl ether represented by the general formula (1), a monomer having a carboxyl group, and vinyl acetate (hereinafter referred to as "copolymer") B "
Is preferably used. In particular, those in which R ¹ is a vinyl group are most preferably used.

R ² can be appropriately selected depending on the type of the dispersion medium, the type of the inorganic powder, and the like. When used in an aqueous dispersion medium, R ² has an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group,
A tetrahydrofurfuryl group or hydrogen is preferred.

The monomer having a carboxyl group is a polymerizable unsaturated carboxylic acid such as itaconic acid, (meth)
An acid anhydride such as acrylic acid, crotonic acid, maleic acid, phthalic acid or maleic anhydride, phthalic anhydride, itaconic anhydride or a salt of a hydrolyzate and / or hydrolyzate thereof, and (meth) acrylic acid Esters such as those obtained by copolymerizing and hydrolyzing esters such as ethyl (meth) acrylate and monomethyl maleate are included. These can be used alone or in combination.

The content of the carboxyl group is not particularly limited, but a content in the range of 0.01 to 20 mol% based on the total amount of the vinyl alcohol unit and the vinyl acetate unit can be suitably used. More preferably, it is 0.1 to 10 mol%.
If it is less than 0.01 mol%, the dispersibility may be reduced,
If it is at least 20 mol%, the water resistance may decrease in a field of application where water resistance is required, for example, in the field of paint, and may cause a problem.

The degree of saponification of the copolymer B is not particularly limited.
Complete saponification or partial saponification may be used. When water solubility is required, those having a saponification degree of 50 mol% or more, preferably 70 mol% or more, particularly 80 mol% or more are most suitably used.

As the method for producing the copolymer B, known polymerization means and polymer reaction means can be arbitrarily applied (for example, JP-A-5-49683). In order to copolymerize vinyl acetate, polyalkylene glycol alkenyl ether, and polymerizable unsaturated carboxylic acids, these unsaturated monomers are polymerized by a known method such as bulk polymerization, solution polymerization, or emulsion polymerization. Can be done. Among them, bulk polymerization or solution polymerization in which a polymerization is carried out without a solvent or in a solvent such as a lower alcohol such as methyl alcohol or ethyl alcohol is industrially suitable. Further, a solvent such as acetone, methyl acetate, and toluene may be contained within a range that does not affect the polymerization. Examples of the initiator used for the copolymerization include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, and n-propyl peroxycarbonate. Known radical polymerization initiators such as azo initiators and peroxides are exemplified. The polymerization temperature is not particularly limited, but is preferably in the range from 40 ° C. to about the boiling point of the solvent or monomer.

The present invention relates to a polycarboxylic acid copolymer having a carboxyl group and a polyalkylene oxide structure in a side chain (copolymer A) and a vinyl alcohol system having a hydroxyl group, a carboxyl group and a polyalkylene oxide structure in a side chain. It is characterized in that it is used in combination with a copolymer (copolymer B), and when used in combination, excellent dispersibility, long-term dispersion stability and hard cake resistance are obtained.

The amount of the copolymer A and the copolymer B is not particularly limited, but may be used in the range of 0.01 to 20% by weight in total of both copolymers based on the powder to be dispersed. preferable. The use ratio of the copolymer A and the copolymer B is 0.01 / 1.
Although it can be used in the range of 1 to 0.01, it is preferably 0.
It is in the range of 2/1 to 1 / 0.2. It can be used in the form of an aqueous solution by dissolving it in water, or when the melting temperature is room temperature or higher, it can be ground and used as a powder.

The dispersing agent of the present invention includes, in addition to the copolymer A and the copolymer B, a wetting agent, an antifoaming agent, a pH regulator, a freeze stabilizer, a thickener, a flow improver, a preservative, and a fungicide. Agents, binder resins, other dispersants and the like can be used in combination.

The dispersant of the present invention may be a powder, especially an inorganic powder,
It can be suitably used for dispersing inorganic pigments, has excellent long-term dispersion stability, and can prevent generation of a hard cake due to sedimentation. Examples of the inorganic powder include an inorganic pigment, an abrasive, and a ceramic powder. Examples of inorganic pigments include white pigments such as titanium dioxide, zinc white, basic lead sulfate, lead white, and lithopone; black pigments such as carbon black, pine smoke (lamp black), bone black, graphite, iron oxide, and iron black. , Red pigments such as chrome vermilion molybdenum red, red iron oxide (iron oxide), graphite, yellow iron oxide, titanium yellow,
Yellow pigments such as ocher (ocher), green pigments such as Clon green, cobalt green and chromium oxide, blue pigments such as ultramarine and navy blue, metal powder pigments such as aluminum powder, bronze powder, copper powder, stainless steel powder, asbestin, Calcium carbonate, clay, diatomaceous earth, white carbon, bentonite,
Extenders such as talc, precipitated magnesium sulfate, barite, precipitated barium sulfate, mica, and gypsum; and pigments for coated paper such as kaolin, satin white, aluminum hydroxide, and titanium white, but are particularly limited to these. Is not done.

In addition, the dispersant of the present invention can be used for dispersing abrasive grains for abrasives or dispersing ceramics. As the target inorganic powder, for example, aluminum oxide,
Abrasive grains and ceramic materials such as zirconia, cerium oxide, silicon carbide, boron carbide, boron nitride, titanium carbide, tungsten carbide, titanium nitride, sialon, silicon nitride, colloidal silica, fumed silica, diamond, corundum, boehmite, garnet, Emery,
Examples include abrasive grains such as silica sand, pumice stone, diatomaceous earth, and dolomite, but are not particularly limited thereto.

[0030]

Next, the present invention will be described in more detail by way of examples.

Six types of copolymer A were prepared, dissolved in water and neutralized with ammonia to obtain a pH 7 polymer aqueous solution.
Table 1 shows the obtained copolymer A.

[0032]

[Table 1]

Six types of copolymer B were prepared. All of the obtained copolymer B was made into a powder. Table 2 shows the obtained copolymer.

[0034]

[Table 2]

Note * 1 Polyalkylene glycol alkenyl ether content (mol%) = polyalkylene glycol alkenyl ether / (vinyl alcohol + vinyl acetate) × 100 * 2 Itaconic acid content (mol%) = itaconic acid / (vinyl alcohol) + Vinyl acetate) × 100 * 3 Saponification degree (mol%) = vinyl alcohol / (vinyl alcohol + vinyl acetate) × 100 * 4 Intrinsic viscosity [η] measured at 30 ° C. using an Ostwald viscometer and ion-exchanged water as a solvent. ] (G / dl), viscosity average degree of polymerization (P) log (P) = 1.613 × log [η] × 10 ⁴ /
8.29

Using a ball mill, 0.98 parts by weight of the copolymer A in Table 1 as a pure component, 0.98 parts by weight of the copolymer B in Table 2, 0.02 parts by weight of a polyether-based defoamer, titanium oxide / CR-550 (Ishihara Sangyo) 20 parts by weight, pure water 80
A titanium oxide slurry consisting of parts by weight was produced. For evaluation of redispersibility, 500 cc of the obtained titanium oxide slurry was transferred to a 75 mm-diameter closed container and allowed to stand at 20 ° C. 2
After standing for 4 weeks, 4 weeks and 12 weeks, the hardness of the slurry was evaluated by the touch when a glass rod weighing 25 g and having a diameter of 6 mm was gently dropped onto the slurry. Next, in the slurry, diameter 50
mm was stirred gently at a rotation speed of 400 rpm for 60 minutes, then the concentration of the upper layer of the slurry was measured by the solid content, and the redispersibility (%) = (slurry concentration after stirring) / (Slurry concentration at the time of adjustment) x 100
Was calculated. Furthermore, to confirm the dispersibility of the re-dispersed slurry, as a coated paper test, a neutral paper was used as a base paper, and the re-dispersed slurry was applied to one side of the base paper to a thickness of 50 μm, and bumps, unevenness, etc. The sample without the mark was marked with "O", and the sample with bumps and unevenness was marked with "x". Table 3 shows the evaluation results.

[0037]

[Table 3]

(Note 1) Criteria for judging cake hardness ：: The glass rod reaches the bottom by its own weight without resistance. Δ: The glass rod reaches the bottom by its own weight, but has a slight resistance. X: Even if force is applied to the glass rod, it does not reach the bottom because of the heart cake layer. Alternatively, a pudding-like aggregated layer is formed.

As is clear from Table 3, the inorganic powder slurry dispersed with the dispersant of the present invention suppresses the formation of a hard cake and an agglomerated layer, has excellent redispersibility even after standing for 12 weeks, and Since there are no bumps or unevenness in the coating test, it can be seen that they have excellent dispersibility and dispersion stabilizing properties, and are easy to handle. On the other hand, as apparent from the comparative example, the copolymer A
It is clear that the copolymer B alone used was inferior in redispersibility and hard cake resistance, and was inferior in performance due to bumps and unevenness. It can be seen that the effect of using the copolymer A and the copolymer B together is remarkable.

[0040]

The dispersant of the present invention has both a dispersing effect and a dispersion stabilizing effect, and is suitable as a dispersing agent for various kinds of powder slurries, especially for inorganic powder slurries.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D077 AB02 AB04 AB05 AB06 AC05 BA01 BA02 BA03 BA07 CA02 CA15 CA17 DD15Y DD16Z DD20Z DD32Y DD32Z DD33Y DD33Z DE02Y DE03Y DE04Y DE07Y DE08Y DE10Y 4G030 AA16 GA16 4G011 AAB03 AB10Y DA06 EA01 EA04 EA10 4J002 BE02X BE04W BE04X BF02X BG01X BH02W BH02X CH05W CH05X FD010 GH01

Claims (5)

[Claims] 1. A dispersion comprising a polycarboxylic acid copolymer having a carboxyl group and a polyalkylene oxide structure in a side chain, and a vinyl alcohol copolymer having a hydroxyl group, a carboxyl group and a polyalkylene oxide structure in a side chain. Agent. 2. The method according to claim 1, wherein the polycarboxylic acid copolymer is a copolymer of polyalkylene glycol alkenyl ether represented by the general formula (1) and maleic anhydride and / or a hydrolyzate thereof. Dispersant. Embedded image (R ¹ is a vinyl group, an allyl group, AO is an oxyalkyl group having 2 to 4 carbon atoms, n is an integer of 1 to 200, R ² is hydrogen,
Or an organic residue such as an alkyl group having 1 to 20 carbon atoms, a phenyl group, a cyclohexyl group, and a tetrahydrofurfuryloxy group) 3. The vinyl alcohol copolymer according to claim 1,
2. A vinyl alcohol copolymer obtained by saponifying a copolymer of a polyalkylene glycol alkenyl ether represented by the above general formula (1), a monomer having a carboxyl group, and vinyl acetate. Or the dispersant according to claim 2. 4. The dispersant according to claim 1, which is for an inorganic powder. 5. A dispersion method using the dispersant according to any one of claims 1 to 4.