JPS5895545A - Dispersant - Google Patents

Abstract

PURPOSE:To decrease settling and to eliminate formation of hard cake by using alpha,beta-unsatd. carboxylic acids, alpha,beta-unsatd. amides or vinyl compds. besides these as constituting components, copolymerizing these components and controlling the viscosity of the aq. solns. thereof to specific conditions. CONSTITUTION:alpha,beta-Unsatd. carboxylic acids, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc., alpha,beta- unsatd. amides, for example, acrylamide, methacrylamide, etc. or vinyl compds., for example, methyl acrylate, ethyl acrylate, propyl acrylate, etc. besides these acids and amides are copolymerized. Any known method may be used for the copolymerization and the viscosity of an aq. soln. of 10wt% the copolymers thereof at 25 deg.C is controlled to 800-2,000cps.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dispersant used for stably dispersing inorganic or organic fine powder in water.

More specifically, it has good dispersibility, and there is little sedimentation of fine powder even when stored for a long time. This invention relates to a dispersant that provides

Slightly water-soluble or water-insoluble inorganic or organic fine powder,
When dispersing the powder in water, various factors such as the difference in specific gravity between water and the fine powder, the average particle size, particle size distribution, and affinity for water of the fine powder, (1) the concentration and viscosity of the dispersion, etc. Dispersibility is interrelated, and if an appropriate balance of these factors cannot be maintained, the fine powder may sink, float to the surface, or remain floating on the surface, resulting in poor dispersion. It becomes impossible to do so.

In general, the specific gravity of fine powder is greater than that of water, so most of the time it settles out, but when a compound called a dispersant, such as a surfactant such as the well-known polyoxyethylene oleyl ether, is added, its action is The fine powder is stably suspended in water to form a dispersion.

However, since this dispersion is inherently thermodynamically unstable, if left for a long time, the fine powder will inevitably settle.

In general, the better the dispersibility of the dispersant, the finer the fine powder that settles out of the dispersion becomes a sediment that is closer to fine grain packing, creating a coagulate that is hard and difficult to redisperse (i.e., a hard cake). When using it after making it, conventional dispersants with excellent dispersibility are
Although these dispersants are very effective, if these dispersants are used when the dispersion is stored for a long time before use (2), a hard cake is formed and redispersibility is poor. arise. In other words, conventional dispersants have a strong effect of loosening fine powder secondary particles into primary particles and preventing separated particles from agglomerating again, but they are insufficient in terms of settling properties and preventing the formation of hard cakes after settling. This is not satisfactory and improvements are desired in this respect.

The present inventors have an excellent dispersion effect on fine powder,
A dispersing agent that prevents sedimentation and hard cake formation after sedimentation, especially conventional dispersion for fine powders with a large average particle size such as those with a specific surface area of 22,000 cd/g or less, which have a high sedimentation property and are prone to hard cake formation. As a result of intensive research to find a dispersant that improves the drawbacks of conventional dispersants, the dispersant of the present invention was completed.

That is, the present invention provides α,β-unsaturated carboxylic acid and α.

Concerning a dispersant consisting of a water-soluble copolymer containing β-unsaturated amide or these and other vinyl compounds, and whose 10% by weight aqueous solution has a viscosity of 800 cps or more and 20,000 cps or less at 25°C (3 ) It is a thing.

By using the dispersant of the present invention, it has become possible for the first time to obtain a dispersion that exhibits little sedimentation even when the dispersion is stored for a long time, and in which the sediment does not form a hard cake.

α, which is a component constituting the copolymer that becomes the dispersant of the present invention
, β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc., and α,β-unsaturated amides include acrylamide, methacrylamide, etc. Vinyl compounds as the third component include α, β-unsaturated carboxylic acids, α, β-unsaturated carboxylic acids,
- All vinyl compounds other than unsaturated amides are included; representative examples include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,
Acrylic acid alkyl esters such as isobutyl acrylate and acrylic 112 ethylhexyl, methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and methacrylic 112 ethylhexyl, acrylic acid dihydroxy Hydroxy esters of acrylic acid or methacrylic acid such as ethyl and dihydroxyethyl methacrylate; vinyl esters such as vinyl acetate and vinyl stearate; unsaturated nitrites such as acrylonitrile and methacrylonitrile; styrene; , vinyl aromatics such as α-methylstyrene, α-chlorostyrene, vinylnaphthalene, and vinyltoluene, esters of unsaturated dicarboxylic acids such as monomethyl itaconate, monomethyl maleate, dibutyl maleate, glycidyl acrylate, Monoglycidyl derivatives such as glycidyl methacrylate and 2-ethylhexyl glycidyl ether; compounds having two or more unsaturated bonds in the molecule such as divinylbenzene, divinyltoluene, diallyl phthalate, ethylene glycol diacrylate or ethylene glycol dimethacrylate; , polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, ethylene glycol diglycidyl ether (5), tyrene glycol derivatives, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamidomethylpropane sulfone Examples include sulfo group-containing compounds such as acids, but the present invention is not limited to these examples, and a wide variety of other generally known vinyl compounds having polymerizability can be used. However, in order to obtain a water-soluble copolymer, the amount of these compounds to be used is necessarily limited, and in particular, the amount of compounds having two or more unsaturated bonds is extremely limited.

In order to achieve the dispersibility, anti-sedimentation properties, and prevention of hard cake formation, which are the features of the dispersant of the present invention, preferred α, β-unsaturated carboxylic acids are acrylic acid or methacrylic acid; The unsaturated amide is acrylamide, and the third component vinyl compound is an acrylic acid alkyl ester or a methacrylic acid alkyl ester in which the alkyl group has 1 to 8 carbon atoms.By combining these, the present invention can be achieved. You can make better use of your strengths.

(6) Various dispersants made of polymers or copolymers of α,β-unsaturated carboxylic acids and their salts have been proposed, but none of them have been proposed for the purpose of sedimentation, which is the object of the present invention. Almost no improvements can be made in terms of properties and prevention of hard cake formation, and all of these are merely aimed at improving dispersibility.

The combination of components constituting the copolymer that becomes the dispersant of the present invention is as follows: (1) α, β-unsaturated carboxylic acid/α, β-unsaturated amide (2) α, β-unsaturated carboxylic acid/ Although there are α,β-unsaturated amides/other vinyl compounds, (2) The copolymer consisting of the components shown in is +1)
It is often superior to those consisting of the ingredients shown in .

The proportions constituting the copolymer that becomes the dispersant of the present invention are configured in order to achieve the object of the present invention (7) 20 to 80 parts by weight of α,β-unsaturated carboxylic acid, based on 100 parts by weight of the entire component , α, β-unsaturated amide 80-20
Parts by weight, the proportion of the vinyl compound is preferably 0 to 60 parts by weight, and a particularly preferable range is α.

20 to 80 parts by weight of β-unsaturated carboxylic acid, 10 to 40 parts by weight of α, β-unsaturated amide, 10 to 40 parts by weight of vinyl compound
It's weight. Here, if the α,β-unsaturated carboxylic acid is less than 20 parts by weight and the α,β-unsaturated amide exceeds 80 parts by weight, the dispersibility will be poor; If the amount of α,β-unsaturated amide exceeds 20 parts by weight, the sedimentation property and prevention of hard cake formation will be poor.

The third component, a vinyl compound, is added as necessary in order to better exhibit the features of the present invention, but in any case, if the amount exceeds 60 parts by weight, the dispersibility will be poor. This is not desirable.

Moreover, in the copolymer used as the dispersant of the present invention, α, β-
The calhoki(8) sil group derived from an unsaturated carboxylic acid is preferably in the form of a salt from the viewpoint of ease of application to an aqueous dispersion. Examples of salt forms include alkali metal salts (lithium, sodium, potassium salts, etc.)
, ammonium salts, and amine salts (methylamine, jetanolamine salts, etc.). Note that there is no harm in leaving unneutralized portions of these carboxyl groups.

To obtain a dispersant suitable for the purpose of the present invention,
In addition to the above-mentioned copolymer components and their component proportions, it is necessary to specify the molecular weight of the copolymer, and only those within a specific molecular weight range have the features that are the object of the present invention. Generally used as a dispersant for various fine powder pigments such as calcium carbonate, kaolin, clay, and satin white.
It is known to use various polymers and copolymers, such as acrylamide/alkali metal salt copolymer of acrylic acid (Japanese Patent Publication No. 46-36883), acrylic acid/
Salt of maleic acid copolymer (JP-A-53-129200)
, high molecular weight polycarboxylic acid or (9) its alkali metal salt (JP-A-53-2557), α, β
- There are salts of copolymers of unsaturated acids/specific vinyl compounds (Japanese Patent Publication No. 5O-23850), but all of these polymers aim to have a molecular weight of 100,000 or less, so-called low molecular weight These low molecular weight polymers are intended to be used as conventionally known dispersants with improved dispersibility, and the use of these low molecular weight polymers is useful for the purpose of the present invention in preventing sedimentation and hard cake formation. In particular, when applied to fine powder with a large average particle size, such as a fine powder with a specific surface area of 220 GOcd/g or less, even if an excellent dispersion effect is obtained, there is a large amount of sedimentation due to standing after dispersion, and a large amount of sedimentation hard cake is generated. Another example is polyacrylamide and acrylamide/acrylic acid copolymers or salts of copolymers with a molecular weight of 8 million to 1.
It is also known that a stable dispersion of zeolite can be obtained by using a polymer having a high molecular weight such as 0 million, which is usually used as a polymer flocculant (Japanese Patent Laid-Open No. 55-84).
533), the addition of polymers with such high molecular weights, which are effective as flocculants10), can reduce the degree of sedimentation and hard cake formation of the dispersion, but the essential dispersibility is poor and the dispersion This increases the viscosity of the dispersion and impairs the fluidity of the dispersion, causing many problems in terms of handling (workability) of the dispersion and practical quality when mixed with other blended raw materials, making it difficult to use in general. It is. That is, as detailed above in the present invention, the constituent components of the copolymer are a binary copolymer containing α,β-unsaturated carboxylic acid and α,β-unsaturated amide as essential components, or α,β- Unsaturated carboxylic acids and α, β-
A dispersant that achieves the objects of the present invention was obtained by using a terpolymer of unsaturated amide and other vinyl compounds and by controlling the molecular weight of the polymer within a specific range. However, when it comes to the molecular weight of these copolymers, there are various difficulties in measuring technology in obtaining accurate absolute values of the molecular weight of the copolymer. It is specified by the solution viscosity of the polymer, and is defined by the viscosity range of a 10% aqueous solution at 25°C, measured with a B-type precision needle at 25°C and a rotor rotation speed of 5 Q rpm (11). l, N” in the copolymer according to the invention
(is 800 cps or more and 20,000 cps or less, preferably 10,000 cps or less. That is, 80
At 0 cps or less, even if the dispersibility is excellent, the sedimentation after dispersion is large and hard cakes are easily formed. Also, 200
If it exceeds 0.00 cps, the dispersibility will be poor, the viscosity of the dispersion will increase, the fluidity will be poor, and the workability will be significantly deteriorated. Although the relationship between the aqueous solution viscosity (800 to 20,000 cps) and the average molecular weight cannot be clearly expressed for the copolymer according to the present invention, the average molecular weight is estimated to be approximately 150,000 to 850,000. .

Although the dispersant and its constituent requirements for achieving the object of the present invention have been described in detail above, the dispersant of the present invention has a structure that has not been clarified in known polymer dispersants, and also has a structure that has not been clarified in conventional polymer dispersants for that purpose. It has excellent effects in terms of dispersibility, anti-settling properties, and prevention of hard cake formation that could not be achieved with conventional dispersants (12). It is.

When using the dispersant of the present invention, the dispersant must be used as a dispersant (
It may be used in an amount of 0.005 to 3% by weight, preferably 0.01 to 1.5% by weight, based on the fine powder+water.

The dispersant of the present invention is effective for both inorganic and organic fine powders. Examples of inorganic powders include titanium oxide, calcium carbonate, clay, zinc oxide, iron oxide, satin white, barium sulfate, white carbon, dark blue,
Examples of organic powders such as ultramarine, carbon black, and aluminum hydroxide include insoluble azo pigments, azo disperse dyes, phthalocyanine pigments, threne dyes, anthraquinone disperse dyes, lake pigments, and coal powder.

In addition, the dispersant of the present invention is not limited in any way by the particle size of the fine powder in use, and shows good effects on particles of any size.
Since fine powders with a relatively large average particle size of 0 d/g or less have a high sedimentation property, by using such fine powders, the effects of the present invention can be particularly brought out (13). The concentration may be any concentration at which a dispersion is produced, generally from 0.5 to 80% by weight, and the dispersant of the present invention can be used at such concentrations without any problems.

When using the dispersant of the present invention, generally known dispersing machines or pulverizers such as an attritor, sand mill, three-roll mill, ball mill, or homogenizer may be used. General aqueous dispersants, anionic and nonionic surfactants, polymeric dispersants such as sodium polyacrylate, olefin/sodium maleate copolymers, etc., and condensed phosphates cannot be used together. Moreover, the dispersant of the present invention can be applied to any field where the above-mentioned inorganic and organic fine powders are used, such as paper processing, textile processing, building material processing, ceramic processing, etc. It can be applied to a wide range of fields such as , pigment production, and paints.

Hereinafter, the present invention will be specifically illustrated with reference to Examples and Comparative Examples.

(14) Examples and Comparative Examples As fine powder, heavy calcium carbonate (specific surface area 3500
cd/g, average particle diameter 6.35μ), the following tests were conducted on various dispersants, and the results shown in the attached table were obtained.

Add the dispersant to a predetermined amount of water, and while stirring with a lab body spar (2000 rpm+), gradually add the above powder. After adding the entire amount, stir for another 10 minutes until the slurry concentration is 7.
A 5% calcium carbonate slurry was obtained. (The pure content of the dispersant was 0.1% based on calcium carbonate.) About the obtained slurry, the dispersibility immediately after blending, and the sedimentation and hard cake formation when the slurry was left at room temperature for 2 days. An evaluation test was conducted and the results shown in the attached table were obtained. As shown in the results, when the dispersant of the present invention was used, it showed good results in all evaluations of dispersibility, sedimentation, and prevention of hard cake formation, and can be said to be an extremely good dispersant. If a dispersant outside the scope of the present invention is used, it may be unsatisfactory in at least one of the evaluation items (1.
5) Shows results and does not serve the purpose of the present invention.

The evaluation method for each test item is as follows.

[Dispersibility] Measure the viscosity immediately after blending Nislary.

(25°C, 60 rpm, read the value after 90 seconds) [Settling property]: The obtained slurry was kept at room temperature without stirring.
・The sample was left for 2 days and visually evaluated to determine whether the particles were dispersed without settling.

○...No sedimentation.

Δ... Slight sedimentation.

×: There is a large amount of sediment.

[Hard cake formation]: Similar to the sedimentation property, the slurry after being left for 2 days was evaluated as follows.

○: No hard cake formation.

△: Cake was formed, but redispersion was easy.

×: Obviously a hard cake is formed and redispersion is difficult.

(16)

Claims (1)

[Claims] α, β-unsaturated carboxylic acid, α, β-unsaturated amide, or these and other vinyl compounds as constituent components, and 10
A dispersant comprising a water-soluble copolymer having a viscosity of 800 cps or more and 20,000 cps or less at 25° C. in a wt% aqueous solution.