JPH0381386A - Water dispersion of thickening agent - Google Patents

Abstract

PURPOSE:To make gathering and sticking of particles to each other difficult when they are dissolved in water by incorporating a powder of a modified alpha-olefin-maleic anhydride copolymer contg. a specified structural unit in the main chain as a main component. CONSTITUTION:An alpha-olefin (A) which is a linear or branched olefin with a C-C unsatd. double bond at an alpha-position and maleic anhydride (B) are radical- polymerized in the presence of a (meth)acrylate (C) of formula I (wherein R is a 10-30C alkyl; n is 0-1) in an org. solvent at 30-150 deg.C for 2-10hr and then ground to obtain the title thickening agent mainly comprising a power of a modified alpha-olefin-maleic anhydride copolymer wherein the structural units based on the component A and the structural unit based on the component B are main components and the structural units of formula II based on the component C in a molar radio of 0.01-0.5 to the structural units based on the component B are incorporated in the main chain and which has an MW of 40,000-700,000 and a mean particle diameter of 10mum or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thickening agent that has the effect of thickening an aqueous solution.

[Conventional technology]

Conventionally, water-soluble thickeners include agar, gelatin, sodium alginate, methylcellulose, CMC1PVA,
Sodium polyacrylate, polyacrylic acid amide,
Polyethylene oxide and the like are known and are used in various applications such as printing paste, fiber wall materials, latex, and thickeners for water-based paints.

Among these water-soluble thickeners, those based on linear synthetic polymers with a high degree of polymerization have poor solubility in water due to their high molecular weight, and not only take a long time to dissolve, but also cause leakage and stickiness. It is inconvenient to handle due to its nature. Another disadvantage is that the viscosity generally changes significantly with respect to temperature. Thickeners made of hyperbranched synthetic crosslinked polymers exhibit thixotropic viscosity behavior without leakage, but the molecular chains are likely to break due to mechanical shearing and the viscosity decreases due to shear stress. It has a significant problem. On the other hand, thickeners made of natural products are susceptible to spoilage and deterioration, are unstable in supply, are expensive, and have limited uses.

Previously, the present inventors have developed a structural unit based on α-olefin (
1) and a structural unit (II) based on maleic anhydride, and the main chain contains the general formula (wherein R represents an alkyl group having 10 to 30 carbon atoms,
n represents an integer of O or 1) (I
an alkali metal salt of a modified α-olefin-maleic anhydride copolymer having a molecular weight of 40.000 to 700.000 and contained in a molar ratio of 0.01 to 0.5 to t);
Water-soluble thickeners made of alkaline earth metal salts or ammonium salts exhibit high viscosity, and not only have good solubility in water, but also have thixotropic viscosity behavior without leakage. They discovered that there was almost no decrease in viscosity due to shear stress, and filed a patent application (patent application 1983).
-083433).

[Problems to be Solved by the Invention] However, further study of this water-soluble thickener revealed that when it is dissolved in water and used, collective adhesion between particles tends to occur (mamako), which makes stirring and dissolution extremely difficult. It has been found that there are problems such as it is time consuming and the viscosity of the obtained aqueous solution tends to be uneven.

[Means for Solving the Problems] According to the present invention, the above problem can be solved by focusing on the particle size of the modified α-olefin-maleic anhydride copolymer and turning it into a powder having a certain average particle size or less. It has been found that the problem can be solved by using

That is, the present invention provides structural units based on α-olefins [
I] and a structural unit (If) based on maleic anhydride, and the main chain has a general formula (wherein R represents an alkyl group having 10 to 30 carbon atoms,
n represents an integer of O or 1) is replaced with a structural unit based on maleic anhydride (I[
) containing a modified α-olefin-maleic anhydride copolymer with a molecular weight of 40.000 to 700.000 in a molar ratio of 0.01 to 0.5, the powder has an average particle diameter of less than 10 μm. This invention relates to an aqueous dispersion type thickener as a component.

The aqueous dispersion type thickener of the present invention has a large thickening effect,
It has advantages such as almost no decrease in viscosity due to mechanical shearing force and thixotropic viscosity behavior with no leakage. (2) Since the aqueous dispersion contains a high concentration of polymer, it can be used as a rubber latex, synthetic resin emulsion, or an aqueous slurry containing inorganic or organic pigments. When used as a thickener for paints, etc., it has the excellent feature of rarely reducing the solid content concentration of the substance to be thickened.

The modified α-olefin-maleic anhydride copolymer (hereinafter sometimes simply referred to as modified copolymer) used in the present invention has the general formula (wherein R represents an alkyl group having 10 to 30 carbon atoms). ,
n represents an integer of 0 or 1).
It is obtained by radical polymerization of an olefin and maleic anhydride in an organic solvent.

The α-olefin used above means a linear or branched olefin having a carbon-carbon unsaturated double bond at the α position. Specific examples include ethylene, propylene, butene-1, butene-2, isobutylene, isoprene, pentene-1, pentene-2,2-methyl-1-
Butene, 2-methyl-2-butene, hexene-1,2-
Methyl-1-pentene, 3-methyl-1-pentene, 4
-Methyl-1-pentene, 2-ethyl-1-butene, 1
．． 3-pentadiene, 1,4-hexadiene, 2.3-
Dimethyl-2-butene, diisobutylene, etc. with 2 or more carbon atoms
12, preferably 2 to 8 olefins. Among these, preferred are olefins having 4 carbon atoms and mixtures thereof (eg, Return B-8), particularly isobutylene. These α-olefins may be used alone or in combination of two or more. The maleic anhydride may also contain maleic anhydride derivatives such as maleic acid, maleic acid monoalkyl ester, maleic acid dialkyl ester, chlormaleic acid, or citraconic acid.

In the present invention, the effect brought about by including the α-olefin-based structural unit (1) in the modified copolymer is that the thickening effect of the thickener continues stably. Unsaturated mono- or dicarboxylic acid and carbon number 10-30
It is known that a copolymer with an acrylic ester having an aliphatic chain length of It is not suitable for the purpose of the present invention because it has poor durability and its viscosity decreases when it is left to heat in a water-containing state. A preferred composition ratio of structural unit (1) and structural unit (II) in the modified copolymer ((
N/(u)) is 1/3 to 3/1 in molar ratio.

Structural units constituting the modified copolymer used in the present invention (
In the above general formula representing Ill), R has 10 carbon atoms.
~30 alkyl groups, such as n-decyl,
n-dodecyl, n-hexadecyl, n-octadecyl,
Straight chain alkyl groups such as n-eicosyl and n-tocosyl, 2
Branched alkyl groups such as -ethylhexyl and t-dotecyl are mentioned.

Among them, examples of compounds represented by the general formula [■], which preferably have a straight chain alkyl group having 10 to 30 carbon atoms, preferably 16 to 30 carbon atoms, include n-decyl methacrylate, n-dodecyl methacrylate, and t-methacrylate. -dodecyl, n-hexadecyl methacrylate, n-tocosyl methacrylate,
Examples include 2-ethylhexyl acrylate.

In the radical copolymerization of α-olefin and maleic anhydride in the coexistence of the acrylic acid ester monomer represented by the general formula (IV), it is preferable to use a common radical polymerization catalyst. .Azobis compounds such as 2'-azobisisobutyronitrile, 2.2'-azobis-1-cyclohexane-l-carbonitrile, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, benzoyl peroxide, perloyl Examples include peroxides such as peroxide.

Examples of organic solvents used during polymerization include acetone, ketones such as methyl ethyl ketone, methyl acetate, ethyl acetate,
Examples include esters such as methyl propionate, ethers such as tetrahydrofuran and dioxane, and alkylbenzenes such as benzene, xylene, toluene, and ethylbenzene. However, when a mixed solvent of ethyl acetate and t-butanol is used, smooth precipitation polymerization results in shape change. A good particulate polymer can be obtained. The polymerization solvent, monomer, and polymerization catalyst may be added all at once at the initial stage of polymerization, or may be added sequentially. The polymerization temperature is usually in the range of 30 to 150"C, but for example, when a mixed solvent of ethyl acetate and t-butanol is used as the polymerization solvent, the temperature is set in the range of 50 to 100"C to ensure smooth precipitation polymerization. It is preferable to set Although the polymerization time can be selected as appropriate, it is preferably about 2 to 10 hours.

In the present invention, the degree of polymerization of the modified copolymer is mainly controlled by controlling the monomer concentration, the amount of catalyst used, and the polymerization temperature. ■
Halides of group metals, general 2N=, HNmi, H! N
It is also possible to adjust the degree of polymerization of the modified polymer by adding amine compounds represented by - or 84N-, ammonium acetate, nitrogen compounds such as urea, mercaptans, etc. at the beginning of the polymerization or during the progress of the polymerization.

The modified α-olefin-maleic anhydride copolymer obtained in this way is usually a coarse powder with an average particle size of 1100 II or more, so by further wet-pulverizing it using water as a dispersion medium, the average particle size is reduced to 10 μm. It can be made into less than a powder.

For wet pulverization, a pulverizer such as a ball mill or an attriter sand grinder can be used. Among them, if a sand grinder is used, it is possible to efficiently pulverize to the desired particle size in a short time. The sand grinder mentioned here is, for example, as disclosed in JP-A No. 58-67781, in which crushed material and dispersion medium are placed in a vessel, and a disk or arm is rotated to generate a shearing force generated by a difference in flow speed. This is a device that performs dispersion and pulverization. During wet pulverization, a surfactant, an antifoaming agent, and an organic solvent may be added as desired. Furthermore, in order to improve the storage stability of the aqueous dispersion after pulverization, a thickener such as carboxymethyl cellulose may be added to prevent the dispersed fine particles from settling.

The solid content concentration of the modified copolymer in wet milling is 20 to 80% from the viewpoint of milling efficiency and ease of handling of the dispersion.
% by weight, preferably in the range of 30-60% by weight.

The powder made of the modified copolymer constituting the present invention is used after being dispersed in water, and the thickening effect can be obtained by adding a basic substance to the aqueous dispersion of the modified copolymer powder. The acid anhydride group derived from the structural unit (II) is neutralized,
This phenomenon occurs when the modified copolymer becomes water-soluble. The powder of the modified copolymer exists stably as a suspension in an acidic or neutral range, so if the thickened material such as latex, emulsion, or inorganic slurry paint is neutral or acidic, After adding and mixing the modified copolymer powder, the viscosity can be increased by adding a basic substance to easily obtain a uniform thickened liquid.

The basic compounds include alkali metal compounds, alkaline earth metal compounds, ammonia, and amines, examples of which include alkali metal compounds such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, and calcium carbonate. or alkaline earth metal compounds, ammonia, and amines such as methylamine, ethylamine, ethanolamine, and aniline.

In the present invention, the modified copolymer powder has an average particle diameter of 1
It is necessary that the average particle diameter of the powder is less than 0 am; if the average particle diameter of the powder is larger than this, the neutralization reaction with the basic substance will be too slow, making it practically impossible to express the dissolution-thickening mechanism near room temperature. Become.

The amount of the basic compound to be used varies depending on the type of the basic compound and the reaction conditions, but is usually 0.4 to 0.4 to 0.4 to the acid anhydride group of the maleic anhydride residue present in the modified copolymer. This is twice the molar amount. As a result, the acid anhydride group in the modified copolymer becomes a carboxyl group, and the carboxyl fund amount l
0.2 to 1 ratio (hereinafter simply referred to as neutralization degree)
A salt of a water-soluble modified copolymer in which the carboxyl group of is turned into a salt is obtained. If the degree of neutralization is too small, the solubility in water will deteriorate, which is not preferable.

The mechanism by which the salt of the modified copolymer exhibits high aqueous solution viscosity at a low degree of polymerization is that the structural unit (I[[) in the molecule has a long-chain alkyl group, and this hydrophobic alkyl group This is thought to be due to the formation of a loose cross-linked structure between molecules. Therefore, unlike crosslinking by chemical bonds, irreversible cleavage of bonds does not occur even when exposed to mechanical shearing, and therefore, it is thought that almost no decrease in viscosity occurs due to shear stress. Furthermore, since it has a kind of structural viscosity due to intermolecular aggregation of hydrophobic groups in an aqueous solution, it exhibits thixotropic viscosity behavior, and because of its low molecular weight, it exhibits almost no leakage. Furthermore, it has surface activity because it has both a hydrophilic group and a hydrophobic group in the molecule,
It can exhibit effects such as emulsification and foaming.

If the content of the structural unit [III) in the modified α-olefin-maleic anhydride copolymer used in the present invention is too small, the thickening effect will be insufficient, while if it is too large, the salt of the modified copolymer will be Since the water solubility is poor, the molar ratio to the structural unit (n) based on maleic anhydride is o, oi ~ 0.5.
It is necessary that the ratio is as follows. Similarly, if the molecular weight of a modified copolymer is too small, the thickening effect will be insufficient, and if it is too large, the solubility in water will be poor. Viscosity [η)
=0.3~3).

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 and Comparative Example 1 318 ethyl acetate was placed in a 11 autoclave equipped with a stirrer.
．． 2 g, t-butanol 212.2 g, maleic anhydride 58.84 g, isobutylene 50.5 g (isobutylene/maleic anhydride molar ratio 1.5), n-tocosyl methacrylate 14.2 g (relative to maleic anhydride). molar ratio 0.06) and 0.69 g of 2.2'-azobisisobutyronitrile (polymerization catalyst), stirred for 30 minutes to perform mixed dissolution and nitrogen substitution, and then heated to 60''C.
Polymerization was carried out for 5 hours. After the polymerization was completed, the internal solution was taken out and filtered and dried to obtain a polymer powder with an average particle size of 90 IIm and a content of particles with a particle size of 10 μm or more at 96% by weight.

From the analysis results by GPC and NMR, the weight average molecular weight of the polymer was 350.000, and methacrylic acid n
- It contained an average of 4.0 tocosyl-based units per molecule.

Using water as a dispersion medium, the polymer powder obtained in the same manner as above was processed using a sand grinder (solid content 30% by weight).
Modified isobutylene-maleic anhydride having a viscosity shown in Table 1 was ground using a 1/4 G batch type sand grinder manufactured by Igarashi Kikai Co., Ltd. for 10 minutes (Comparative Example 1) and 60 minutes (Example 1), respectively. An aqueous dispersion of acid copolymer was obtained.

Example 2 and Comparative Example 2 Ethyl acetate 397 in a 1i autoclave equipped with a stirrer
．． 8 g, t-butanol 132.6 g, maleic anhydride 58.84 g, isobutylene 63.3 g (isobutylene/maleic anhydride molar ratio 2.0), n-dodecyl methacrylate 45.78 g (maleic anhydride 0.30) and 0.69 g of 2.2'-azobisisobutyronitrile, and polymerization was carried out at 65° C. for 6 hours in the same manner as in Example 1. After the polymerization was completed, the internal solution was taken out and filtered and dried to obtain a polymer powder with an average particle size of 110 μm and a content of particles with a particle size of 10 μm or more at 97% by weight.

From the analysis results by GPC and NMR, the weight average molecular weight of the polymer was 205,000, and it contained an average of 10.5 units based on n-dodecyl methacrylate per molecule.

Polymer powder obtained in the same manner as above was processed using a sand grinder at a solid content of 30% by weight using water as a dispersion medium for 00 minutes (Comparative Example 2) and 60 minutes (Example 2).
The mixture was pulverized to obtain an aqueous dispersion of a modified isobutylene-maleic anhydride copolymer having the particle size shown in Table 1.

Example 3 and Comparative Example 3 In a 11 autoclave equipped with a stirrer, 26 ethyl acetate was added.
5.2 g St-butanol 265.2 g, maleic anhydride 58.84 g, styrene 65.53 g,
(mole ratio of styrene/maleic anhydride 1.05), 21.3 g of n-tocosyl methacrylate (mole ratio to maleic anhydride 0.09), and 0.69 g of 2.2゛-azobisisobutyronitrile. , Polymerization was carried out at 65° C. for 6 hours in the same manner as in Example 1. After the polymerization was completed, the internal solution was taken out and filtered and dried to obtain a polymer powder with an average particle size of 130 μm and a content of particles with a particle size of 10 μm or more at 98% by weight.

According to the analysis results by GPC and NMR, the weight average molecular weight of the polymer is 183.000, and it is a modified styrene-maleic anhydride copolymer containing an average of 6.2 units based on n-tocosyl methacrylate per molecule. Met.

Polymer powder obtained in the same manner as above was processed using a sand grinder at a solid content of 40% by weight using water as a dispersion medium for 10 minutes (Comparative Example 3) and 60 minutes (Example 3).
Modified styrene that has been pulverized and has the particle size shown in Table 1.
An aqueous dispersion of maleic anhydride copolymer was obtained.

Table ■ Usage Examples 1 to 3 and Comparative Usage Examples 1 to 3 An aqueous dispersion with a solid content of 2% by weight obtained by diluting the pulverized aqueous dispersion obtained in Examples 1 to 3 with distilled water. Neutralization degree 0.
Add sodium hydroxide or ammonium hydroxide equivalent to 9 and stir at room temperature.
The viscosity was measured at 20 rpm using a B-type viscometer. (Usage Examples 1 to 3) Similarly, the pulverized aqueous dispersions obtained in Comparative Examples 1 to 3 were diluted with distilled water, and the obtained aqueous dispersions with a solid content of 2% by weight were added to the aqueous dispersions with a neutralization degree of 0. Sodium hydroxide or ammonium hydroxide corresponding to No. 9 was added and stirred at room temperature, and the state of dissolution and the viscosity of the solution at 30° C. were measured using a B-type viscometer at 20 rpm. (Comparative usage examples 1 to 3
) From the results shown in Table 2, an aqueous dispersion consisting of polymer particles with an average particle diameter of less than 10 μm dissolves in a short time at room temperature;
A homogeneous and thickened aqueous solution is obtained, whereas an aqueous dispersion consisting of polymer particles with a particle size of 10°C or more remains undissolved even after long periods of stirring, making it difficult to obtain a homogeneous aqueous solution. I know that I can't get it.

The following margins [Effects of the invention] The aqueous dispersion type thickener of the present invention has a large thickening effect;
It has advantages such as almost no viscosity decrease due to mechanical shearing force, and thixotropic viscosity behavior with no leakage.In addition, (1) it does not cause lumps and is stable at room temperature. (2) Since the aqueous dispersion contains a high concentration of polymer, it can be mixed with rubber latex, synthetic resin emulsion, inorganic or organic pigments, etc. (3) When used as a thickener for aqueous slurries, paints, etc. containing p.
In an acidic or neutral region, L() exists stably as a suspension as fine particles, so if the material to be thickened, such as latex, emulsion, inorganic slurry, or paint, is neutral or acidic, It has the excellent feature that after adding and mixing the polymer powder, it can be thickened by adding a basic substance to easily create a uniform thickened liquid.

Claims (1)

[Scope of Claims] Mainly consists of a structural unit [I] based on an α-olefin and a structural unit [II] based on maleic anhydride, and has a general formula ▲ mathematical formula, chemical formula, table, etc. in the main chain ▼ (in the formula , R represents an alkyl group having 10 to 30 carbon atoms,
n represents an integer of 0 or 1) [III] is the structural unit [II] based on maleic anhydride.
A modified α-olefin-maleic anhydride copolymer with a molecular weight of 40,000 to 700,000 contained in a molar ratio of 0.01 to 0.5 with an average particle diameter of 1
An aqueous dispersion type thickener whose main component is powder less than 0 μm.