KR101121761B1 - A Preparation process of dispersant for increasing dispersion stability of pigment or non-aqueous dye, and dispersion prepared by using the same - Google Patents

Abstract

The present invention relates to a process for the preparation of polymeric dispersants for stabilizing pigments or non-aqueous dyes in ultrafine form in water or in organic solvents with slightly polarity.

Description

A preparation process of dispersant for increasing dispersion stability of pigment or non-aqueous dye, and dispersion prepared by using the same

The present invention relates to a method for producing a polymeric dispersant for stabilizing pigments commercially used in the form of ultra fine particles in water or an organic solvent having a slight polarity. In particular, the present invention relates to a polymeric dispersant that has excellent ability to stabilize at low viscosity and exhibits different characteristics from conventional dispersants that stabilize particles at high viscosity.

Conventional low-viscosity dispersants include Johnson Polymer's John Cryl, but this product is a copolymer of styrene and acrylic acid, showing limitations in various pigments.

Since pigments or disperse dyes are generally dispersed and used, dispersion is very important. Pigments are commonly used in paints to achieve high viscosity dispersion, so the development of low viscosity pigment dispersions is not high.

However, the development of low viscosity dispersions has been very important in recent years. This is due to the fact that recently, the use of pigments in chemical materials has been increasing in the use of electronic components, and thus a high functional low viscosity pigment dispersion is required. In particular, the color filter photoresist used in the manufacture of the color filter for TFT LCD is a very important material for low viscosity pigment dispersion.

In addition, in order to improve the color filter manufacturing process, a color filter inkjet ink, which is a substitute for photoresist, also has a low viscosity pigment dispersion. Most importantly, the physical properties of the dispersant required to prepare such low viscosity dispersions should be excellent. Heat resistance, chemical resistance, and mechanical properties that maintain the strength beyond specified after curing should be satisfied. For example, in the color filter manufacturing process, there is a process of curing at 220 ° C. for 1 hour or more, and ink jet ink requires a highly functional pigment dispersion that can maintain the stability of the dispersion system even at very high temperature of 300 ° C. or higher to generate bubbles.

In recent patents, many patents using commercialized styrene and acrylic acid copolymer products have been registered. In particular, US Pat. No. 6,809,128 No. 6,765,039 The preparation of low-viscosity pigment dispersions using the polymeric dispersants commercialized in the present invention is described in detail. However, these commercialized products have a limited specification and thus have limitations in dispersing various kinds of pigments.

 The present inventors have conducted research to overcome these limitations and have come up with a polymer type dispersant that can be used in water-soluble and organic solvents. The present invention relates to a method for synthesizing a dispersant which can be applied to various types of pigments with low viscosity dispersion stability using various kinds of monomers.

In the present invention, R'-CH ₂ CH ₂ R ² which is a monomer having affinity with the benzene or alkyl group of the pigment, wherein R 'is C ₁ which may be substituted by phenyl, benzyl ester or C _1-6 alkyl _-6 alkyl ester, R ² is H or C _1-4 alkyl, methacrylic acid having affinity with the solvent and R '"-CH ₂ CH ₂ R ³ having mechanical strength, wherein R' Is a C _1-6 alkyl ester which may be substituted with hydroxy and R ³ is H or C _1-4 alkyl) to synthesize a polymeric dispersant of Formula 1 having the following diversity:

Where                     

Each A is independently H or C _1-4 alkyl,

R is a C _1-6 alkyl ester which may be substituted by phenyl, benzyl ester or C _1-6 alkyl,

R ¹ is a C _1-6 alkyl ester which may be substituted with hydroxy,

R ″ is H or monovalent metal, but in the case of monovalent metal, it represents O and O ⁻ M ⁺ form,

X is 0.3 to 3.0,

Y is from 0.2 to 2.5,

Z is 0.3 to 3.0.

Examples of the monomer having affinity with the benzene or alkyl group of the pigment include styrene, benzyl methacrylate, 2-ethylhexyl methacrylate, and examples of the monomer having mechanical strength are 2-hydroxyethyl methacrylate. , Methyl methacrylate, butyl acrylate and the like. The monomer used is not limited to only the monomers listed above. In addition, various monomers such as methyl methacrylate, glycidyl methacrylate, etc. which are commercially available may be used in the present invention.

In the present invention, alkyl may be a straight or branched chain having 1 to 6 carbon atoms.

The reaction solvent used for the synthesis of the polymeric dispersant may use both a protic solvent and an aprotic solvent except for water. Protic solvents include butyl alcohol, isopropyl alcohol, ethyl alcohol, and the like, and aprotic solvents include propylene glycol monomethyl ether acetate, dipropylene glycol methyl ether acetate, and diglyme. It can be used as a solvent.

The molecular weight of the high molecular weight dispersant required for the low viscosity pigment dispersion is very important in the molecular weight range of 1,000 to 100,000, preferably 5,000 to 50,000, more preferably 10,000 to 20,000. The molecular weight of the polymer is usually from 100,000 to more than one million, but the polymer used as a low viscosity dispersant can be low viscosity dispersion, can be used in a special environment, such as inkjet ink, and can exhibit performance.

The control of the molecular weight of the polymer to be synthesized depends on the concentration and temperature in the reaction and the amount of initiator used. If the concentration and reaction temperature are high and the amount of initiator used is large, the molecular weight becomes small. The reaction concentration is 5% to 60% by weight of the total monomer, preferably 10% to 40%, and more preferably 15% to 30%. Reaction temperature is 50 degreeC-120 degreeC, Preferably it is 60 degreeC-100 degreeC, More preferably, it is 70 degreeC-90 degreeC.

2,2'-azobisisobutyronitrile (AIBN) is used as the reaction initiator, and the amount of use is 0,1% to 10% by weight based on the total monomers used, and preferably 0.5% to 5%. Up to%, more preferably from 2% to 4%.

The polymer in the present invention is a random type polymer and shows excellent efficacy in dispersing characteristics. The synthesized polymer may be pulverized in various pulverizers by removing the reaction solvent or by mixing with an appropriate amount of pigment in the present state. Depending on the type of pigment, it can typically be applied from 20% to 150% by weight of the pigment.                     

In addition, when used in an aqueous solution, the effect of low viscosity dispersion can be seen only by dissolving in water with a base such as sodium hydroxide, potassium hydroxide, ammonia or the like. When used in an organic solvent can be used directly mixed with the pigment without strong base treatment. In the synthesis of the polymer dispersant, the structure itself is composed of three components, a portion having an affinity with an organic pigment, a portion having an affinity with a solvent, and a portion having mechanical properties of the dispersant itself.

Monomers of the part having affinity with the pigment include benzyl methacrylate, styrene, etc., monomers of the part having mechanical properties are 2-hydroxyethyl methacrylate, butyl methacrylate, methyl methacrylate, The part having affinity with the solvent is methacrylic acid.

The use ratio of the monomers varies in proportion and type depending on the purpose of application. The optimum ratio and type should first be adjusted based on the polarity of the pigment, the desired viscosity and the properties of the solvent to be used.

The dispersion stabilization mechanism is known to be due to the anion electrostatic repulsion of the carboxyl groups contained in the dispersant surrounding the pigment particles in the case of an aqueous solution, and the steric hindrance effect of the dispersant surrounding the pigment particles in the case of an organic solvent. In other words, stabilization in aqueous solution is a key element to introduce an anion into a carboxyl group with a strong base as described above. Stabilization in organic solvents does not require the introduction of anions, but the carboxyl group of methacrylic acid has affinity with the organic solvent in the structure, and stabilizes. .

The pigment is pulverized into fine particles to be supplied in powder form, and the wetting effect of releasing air adhering to the surface during dispersion to allow water or solvent to penetrate the pigment surface is also a characteristic of the dispersant.

 As a simple example, the present invention is as follows. Dispersants usable in aqueous solution are subjected to the following procedure. Benzyl methacrylate, methyl acrylate, and methacrylic acid were mixed well with butyl alcohol at a molar ratio of 0.7, 0.5, and 1.5, respectively, and the temperature was added to the initiator (AIBN) at about 100 ° C as described above. React while maintaining.

Upon completion of the reaction, the solvent used was removed by vacuum distillation to obtain white crystals of a solid component. The synthesized dispersant has the following Chemical Formula 2.                     

Where

X, Y and Z are relative molar ratios, and for dispersants used in aqueous solution, X is 0.3 to 3.0, Y is 0.2 to 2.5 and Z is 0.3 to 3.0.

If necessary, two or more kinds of monomers having affinity with the pigment may be used (see Examples).

In order to be usable in aqueous solution, a dissolution process is required, and the dissolution process is adjusted to pH 5 to 9 by adding caustic soda, so that the carboxylic acid in the structure is converted to an anion so that it is soluble in water. The chemical structure converted to an anion is represented by the following formula (3).

Where                     

X, Y and Z are as mentioned above in relative molar ratios.

After the pigment is added to the dissolved aqueous solution, it is subjected to a wet process, and subjected to a grinding process using a bead mill or a microfluidizer to prepare a low viscosity pigment dispersion. Pigment dispersion can usually be dispersed by adjusting the concentration of the pigment to about 15% of the total dispersion, the viscosity is low viscosity of about 10cP can be used immediately applied to the inkjet ink. Above all, the dispersion should be subjected to stability testing since the particles should not be crushed, precipitated or separated after grinding. Stability is measured using a particle size analyzer to observe changes in stability over time and accelerated testing for observation in a short time. Time-lapse stability acceleration test is performed for 4 hours at 60 ℃, 4 hours at -10 ℃ and repeated four times to observe the change in particle size. The invention is not limited to these examples.

Dispersants usable in organic solvents go through the following steps: The styrene, butyl methacrylate, and methacrylic acid molar ratios of 1.5, 0.5, and 0.3 are respectively mixed with diglyme, and the initiator is added at a reaction temperature of 80 deg. The structure of the dispersant usable in the organic solvent is shown in the following formula (4).

Where

X, Y and Z are used dispersants in aqueous solution in relative molar ratios, where X is 0.3 to 3.0, Y is 0.2 to 2.5 and Z is 0.3 to 3.0.

If necessary, two or more kinds of monomers having affinity with the pigment may be used (see Examples). In the case of the dispersant used in the organic solvent, methacrylic acid may be used in less than half as compared to the dispersant used in the aqueous solution to obtain good results.

The organic solvent used during the reaction may be mixed with the pigments immediately without separation and then wetted, and then ground in a bead mill or a microfluidizer to prepare a pigment dispersion based on the organic solvent. The above description is also to aid the understanding of the present invention, and the present invention is not limited to the above description.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these are only for the understanding of the present invention and are not intended to be limiting.

Example 1

Benzyl methacrylate (0.07 moles, 12.3 g), methyl methacrylate (0.07 moles, 7.0 g) and methacrylic acid (0.15 moles, 12.9 g) are mixed with 128 g of butyl alcohol and a small amount of nitrogen is passed through. After raising the mixture to 100 ° C., 0.28 g of an initiator (AIBN) was added thereto, followed by reaction for 5 hours while maintaining the temperature at 100 ° C. Nitrogen continues to pass through the reaction to prevent contact with oxygen in the air so that the produced radicals do not disappear. After completion of the reaction, the butyl alcohol was removed using a rotary distillation to obtain 31 g of a polymeric dispersant in a yield of 96%. 30 g of the produced solid was added to 70 g of distilled water, and 50% of sodium hydroxide solution was added to adjust the solution to pH 7.

Example 2

In Example 1, styrene (0.07 mol, 7.3 g) was added instead of benzyl methacrylate and synthesized in the same manufacturing process to obtain 26.3 g of a white solid in a yield of 97%. The dissolution process in aqueous solution is also the same as in Example 1.

Example 3

In Example 1, 2-hydroxyethyl methacrylate (0.07 mol, 9.1 g) was added instead of methyl methacrylate to be synthesized in the same manufacturing process to give 32.6 g of a white solid in a yield of 95%. The dissolution process in aqueous solution is also the same as in Example 1.

Example 4

Benzyl methacrylate (0.04 moles, 7.0 g), styrene (0.03 moles, 3.1 g) methyl methacrylate (0.07 moles, 7.0 g) and methacrylic acid (0.15 moles, 12.9 g) are mixed with 128 g of butyl alcohol Pass a small amount of nitrogen. After raising the mixture to 100 ° C., 0.28 g of an initiator (AIBN) was added thereto, followed by reaction for 5 hours while maintaining the temperature at 100 ° C. Nitrogen continues to pass through the reaction to prevent contact with oxygen in the air so that the produced radicals do not disappear. After completion of the reaction, if the butyl alcohol is removed using a rotary distillation machine, 28.5 g of a polymeric dispersant can be obtained in a yield of 95%. 28 g of the resulting solid was added to 70 g of distilled water and 50% of sodium hydroxide solution was added to adjust the solution to pH 7.

Example 5

Benzyl methacrylate (0.04 moles, 7.0 g), styrene (0.03 moles, 3.1 g) methyl methacrylate (0.05 moles, 5.0 g), methacrylic acid (0.03 moles, 2.6 g) 60 g of propylene glycol methyl Mix in ether acetate and pass nitrogen in small portions. After raising the mixture to 80 ° C., 0.35 g of an initiator (AIBN) was added thereto, followed by reaction for 5 hours while maintaining the temperature at 100 ° C. Nitrogen continues to pass through the reaction to prevent contact with oxygen in the air so that the produced radicals do not disappear.

Example 6

In Example 5, instead of benzyl methacrylate, 0.07 mol 7.3 g of styrene was used to synthesize a polymer dispersant for an organic solvent.

Example 7

50 g of the aqueous polymeric dispersant synthesized in Example 1 was mixed well with 15 g of Pigment Red No. 122 of Clariant Corporation and 50 g of distilled water, followed by well stirring for 2 hours to wet. Into this, 300 g of sand were put and pulverized at rpm 3,000 for 5 hours using a 7 cm diameter disc. When grinding is completed, sand is removed using a pole. A red pigment dispersion having a size of 212 nm of average particle is obtained.

Example 8

50 g of the polymeric dispersant synthetic solution prepared in Example 5 and 10 g of Pigment Red No. 254 were mixed well and stirred for 1 hour. Into this, 100 g of 0.3 mm zirconia beads were put and pulverized at rpm 3,000 for 3 hours using a 7 cm diameter disc. Once grinding is complete, remove the beads using a whisk. A red pigment dispersion with an average particle size of 85 nm is obtained.

Comparative Example 1

20 g of Johnson Polymer Co., Ltd. John Krill 678 is added to 80 g of distilled water and 50% of sodium hydroxide solution is adjusted to pH 7. 50 g of the prepared dispersant solution, 15 g of Pigment Red No. 122 of Clariant Inc., and 50 g of distilled water were mixed well and stirred for 2 hours to wet. 300 g of sand is added to this and ground using a 7 cm diameter disc for 5 hours at rpm 3,000. When grinding is completed, sand is removed using a pole. A red pigment dispersion with an average particle size of 243 nm is obtained.                     

Comparison of Particle Size and Stability over Time Using the dispersant synthesized in Example 1
Pigment Red No. 122 Dispersion John Krill 678 of Johnson Polymers
Used Pigment Red No. 122 Dispersion Before time stability test 212 nm 243nm After time stability test 215 nm 255 nm

As can be seen from the table, in particular, the polymeric dispersant prepared according to the present invention significantly reduces the size of the particles compared to the existing John Krill products, and shows good stability with little change in the size of the particles even with time stability. have.

In the case of using the dispersant prepared according to the present invention, as described above, the ability to stabilize dispersion at low viscosity is excellent, thereby showing a good effect in dispersion of low viscosity ink or paint.

Claims (7)

R'-CH ₂ CH ₂ R ² , wherein R 'is a C _1-6 alkyl ester which may be substituted by phenyl, benzyl ester or C _1-6 alkyl, and R ² is H or C _1-4 alkyl At least one monomer, a methacrylic acid monomer and R '"-CH ₂ CH ₂ R ³ , wherein R'" is a C _1-6 alkyl ester which may be substituted with hydroxy, and R ³ is H or A monomer of C _1-4 alkyl) is dissolved in a solvent and an initiator is used to prepare the polymeric dispersant of formula (I): [Formula 1]

Where Each A is independently H or C _1-4 alkyl, R is a C _1-6 alkyl ester which may be substituted by phenyl, benzyl ester or C _1-6 alkyl, R ¹ is a C _1-6 alkyl ester which may be substituted with hydroxy, R ″ is H or monovalent metal, but in the case of monovalent metal, it represents O and O ⁻ M ⁺ form, X is 0.3 to 3.0, Y is from 0.2 to 2.5, Z is 0.3 to 3.0. The method of claim 1 wherein the solvent is a protic or aprotic solvent. The process according to claim 1, wherein the reaction temperature is 50 ° C to 120 ° C. The method of claim 1 wherein the initiator is 2,2′-azobisisobutyronitrile. The method of claim 1, wherein the dispersant is dissolved in a strong base, converted to a carboxyl anion group, and dissolved in an aqueous solution. A process for producing a pigment or dye dispersion by mixing and grinding the dispersant according to any one of claims 1 to 5 with a pigment or a disperse dye. An inkjet ink prepared using a pigment or dye dispersion prepared according to the method of claim 6.