JPS6245885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous slurry dispersion in which polymer particles are stably dispersed in water. In other words, some aqueous dispersions can be clearly distinguished as hydrosols, emulsions, and suspensions depending on the particle size and dispersion state of the dispersoid, while others have a wide particle size distribution and have the appearance of a slurry as a whole. There is something to show. The present invention relates to a method for producing the above-mentioned slurry-like water dispersion using polymer particles as dispersoids.

Conventionally, as a method for producing such a slurry-like water dispersion, it is known to pulverize a polymer, add it to water, and then disperse it by stirring at high speed. The problem was that the aqueous dispersion had poor storage stability, and the polymer particles separated and settled within a short period of several minutes after being slurried. For this reason, measures are generally taken to improve the stability by adding surfactants, solvents, etc. to the aqueous dispersion.

However, when a water dispersion is formed into a film, the addition of surfactants impairs water resistance, causes discoloration, and causes other impurity-like effects, which poses problems in the application of slurry water dispersions to various applications. Easy to occur. Furthermore, the addition of a solvent causes the polymer particles to sag, increasing the viscosity of the aqueous dispersion, making it impossible to achieve a high concentration, and the effect of such addition on improving stability cannot be said to be that remarkable. .

The present invention aims to provide a new and useful method for producing a slurry water dispersion that can improve storage stability without causing any problems such as water resistance as described above, and its gist is as follows: 0.1 to 35% by weight of an unsaturated monomer having an acidic group and 99.9 to 65% by weight of other unsaturated monomers that can be copolymerized with this monomer
and a copolymer with a weight average molecular weight of 10 ⁴ to 10 ⁶ obtained by copolymerizing with a small amount of unreacted unsaturated monomer used in the above copolymerization, and 0 to 20% by weight of an organic solvent. Prepare a raw material containing substantially no other medium, add an alkali or alkaline aqueous solution to neutralize some or all of the acidic groups in the copolymer molecule, and then further add water. A method for producing a slurry-like water dispersion, characterized in that a slurry-like water dispersion in which the above-mentioned copolymer is stably dispersed in water is obtained by phase inversion.

In this way, the present inventors discovered that the copolymer may contain a small amount of unreacted unsaturated monomer together with a specific copolymer having an acidic group in its molecule, and may also contain a small amount of organic solvent. prepared a raw material substantially free of water or other media, added an alkali or aqueous alkaline solution to neutralize the acidic groups, and caused a phase inversion phenomenon by adding water. It has been found that a slurry-like aqueous dispersion with extremely excellent storage stability can be obtained. Since the slurry-like water dispersion obtained by this method does not contain a surfactant, even when it is formed into a film, there is no deterioration in water resistance, etc. While the method of adding a solvent after producing an aqueous dispersion had drawbacks such as the inability to achieve a high concentration, this problem does not occur even if some organic solvent is contained in the raw materials, and the dispersion is relatively low. It was found that a slurry-like water dispersion with high viscosity and high concentration can be easily produced.

In this invention, unsaturated monomers having acidic groups
In copolymerizing 0.1 to 35% by weight and 99.9 to 65% by weight of other unsaturated monomers copolymerizable with this, conventionally known methods such as bulk polymerization, solution polymerization, emulsion polymerization, pearl polymerization, etc. Either method can be used, but bulk polymerization method and 20% by weight method are particularly preferred.
This is a solution polymerization method using organic solvents. In these two polymerization methods, the resulting copolymer can be used as it is as a raw material for obtaining a slurry-like aqueous dispersion.

In this invention, it is important that a part of the unsaturated monomer used in the copolymerization remains in the raw material as an unreacted product, and when this unreacted product is completely absent, slurry water is It is difficult to obtain a dispersion, and the result is generally a hydrosol with a very small polymer particle size, resulting in poor results in terms of viscosity properties.

The amount of the above-mentioned unreacted unsaturated monomer depends mainly on the amount of the unsaturated monomer having an acidic group used, and when the amount of the above-mentioned monomer used is small, the unreacted material is at least slurry-like water. It is easy to obtain a dispersion,
Conversely, when the amount of the monomer used is large, it becomes difficult to obtain a slurry-like aqueous dispersion unless the amount of unreacted substances is increased. Therefore, the amount of unreacted substances should be determined depending on the amount of the unsaturated monomer having an acidic group used, but it is generally recommended to set it appropriately within the range of about 2 to 30% by weight.

In addition, in making the above settings, consideration should also be given to the storage stability of the slurry-like water dispersion. That is, in the slurry-like aqueous dispersion of the present invention, there is a tendency that the smaller the amount of unreacted substances is, the better the storage stability is, and the more the unsaturated monomer having an acidic group is, the better the storage stability is. Therefore, as a most preferred embodiment of the present invention, the amount of the unsaturated monomer having an acidic group used is set to an optimum range that is neither too large nor too small, and the amount of unreacted monomer that is optimally adjusted accordingly. It is a matter of quantity.

In this invention, the above bulk polymerization method and 20
When obtaining copolymers by polymerization methods other than solution polymerization using organic solvents up to % by weight, i.e., ordinary solution polymerization using large amounts of organic solvents, emulsion polymerization, pearl polymerization, etc. It is necessary to remove the medium used in each polymerization method after polymerization. For example, in the solution polymerization method, the organic solvent in the system is removed by means such as distillation until it becomes 20% by weight or less, particularly preferably until it is completely eliminated. If the amount of the organic solvent exceeds 20% by weight, it will interfere with the production of a slurry-like water dispersion. Further, in the emulsion polymerization method, water is removed by coagulating and separating by salting out, and in the pearl polymerization method, water is removed by filtering the particulate copolymer. In these water removal steps, the emulsifier used during copolymerization is removed together.

Even when the above copolymerization method is adopted, the copolymer must contain a small amount of unreacted unsaturated monomer, but this unreacted material is removed at the same time in the medium removal step. There is a risk that this may occur. In this case, the corresponding unsaturated monomer can be added to the copolymer solid in the above proportion after the medium removal step, thereby making it possible to practically produce a slurry-like aqueous dispersion. Become.

Examples of unsaturated monomers having acidic groups used in this invention include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid,
Unsaturated carboxylic acids having a carboxyl group as an acidic group such as fumaric acid, styrene sulfonic acid, allyl sulfonic acid, sulfopropyl acrylate,
2-acryloyloxynaphthalene-2-sulfonic acid, 2-methacryloyloxynaphthalene-2
Examples of acidic groups include unsaturated sulfonic acids having a sulfonic group, such as sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acryloyloxybenzenesulfonic acid, and other acids having an acidic group. One or more of these may be used.

The amount of the above unsaturated monomer used is 0.1 of the total monomers.
For example, in the case of unsaturated carboxylic acids, it is particularly preferably 0.5 to 20% by weight,
In addition, in the case of unsaturated sulfonic acids, particularly preferred
It is 0.2-10% by weight. If this usage amount is less than 0.1% by weight or exceeds 35% by weight,
In either case, a slurry-like aqueous dispersion with excellent storage stability, which is the object of the present invention, cannot be obtained. That is, if the amount is less than 0.1% by weight, even if a slurry-like aqueous dispersion can be obtained, the storage stability will be significantly poor, and the copolymer particles will easily separate and settle, and if the amount is less than 35% by weight, If the amount is too large, the desired aqueous dispersion cannot be obtained because it becomes water-solubilized instead of being slurried.

Other copolymerizable unsaturated monomers used in combination with such unsaturated monomers can be arbitrarily selected from various ethylenically unsaturated monomers. For example, an alkyl group having 1 to 15 carbon atoms, preferably 3 to 10 carbon atoms, acrylic esters and methacrylic esters, other vinyl ethers, vinyl esters, acrylonitrile, acrylamide, hydroxyalkyl acrylates, styrene, vinyl chloride, ethylene, etc. Examples include ethylenically unsaturated monomers having a functional group such as an amino group, and one or more of them are selected and used depending on the purpose of use.

In addition, various general organic solvents can be used as the organic solvent when employing the solution polymerization method, but in particular, a mode in which solution polymerization is carried out with a solvent amount of 20% by weight or less and no or almost no solvent is removed afterwards. In this case, it is preferable to use an alcoholic hydrophilic solvent such as methanol, ethanol, n-butanol, n-propanol, isopropyl alcohol, or sec-butanol, or an oligomer having a hydrophilic group such as a hydroxyl group, a carboxyl group, or an amino group. The use of prepolymers is preferred.

It is necessary that the weight average molecular weight of the copolymer synthesized by each of the above methods is set in the range of 10 ⁴ to 10 ⁶ . The reason for this is as follows.
If it is less than 10 ⁴ , the physical properties such as cohesive force and physical strength will be poor when it is made into a coating or other molded product, and if it exceeds 10 ⁶ , it will have a high viscosity that will interfere with the alkaline treatment. This is because it becomes difficult to produce a slurry-like water dispersion.

In this invention, by the above-described method, a copolymer having a specific molecular weight and an unreacted unsaturated monomer are contained, and in addition to 0 to 20% by weight of an organic solvent, water or other medium is added. After preparing raw materials that do not contain any substances (only a small amount is allowed),
This raw material is neutralized by adding an alkali or aqueous alkali solution while stirring. The treatment temperature at this time is kept at a constant temperature depending on the type and properties of the copolymer, but is generally 40 to 95°C. The alkali or alkaline aqueous solution used for the neutralization treatment includes ammonia, aqueous ammonia, caustic soda, caustic alkali aqueous solution such as caustic potash, etc., and usually has a concentration of about 1/2 with respect to acidic groups such as carboxyl groups and sulfonic groups of the copolymer. It may be used in a proportion of 15 to 2 equivalents.

After the neutralization treatment is carried out in this manner, water is gradually added while stirring is continued and mixed well. After a certain period of time, a so-called phase inversion phenomenon occurs, and water forms a continuous layer, producing an O/W type slurry water dispersion in which copolymer particles are dispersed.
The solid content concentration of this slurry water dispersion can be freely adjusted, and its viscosity is low even at high concentrations. That is, the viscosity is generally 30 to 500 centipoise at 25°C, and the solids concentration is usually 30 to 70% by weight.

In the production of the slurry water dispersion described above, various additives such as tackifiers, softeners, plasticizers, crosslinking agents, fillers, and colorants may be added at any stage in the production process, that is, before copolymerization. Alternatively, it can be added before or after water dispersion by adding alkali and water after copolymerization to improve the properties of the slurry water dispersion or the physical properties of molded products obtained therefrom.

The slurry-like aqueous dispersion thus obtained has excellent storage stability as described above, and can be cast onto a carrier to form a film or hardened into other molded products. In some cases, it exhibits sufficiently satisfactory performance in terms of water resistance and other physical properties. Therefore, its application range is wide, and it can be effectively used in various fields such as paint, paper, sizing materials, adhesives, overcoat materials, exterior materials, interior materials, packaging materials, and films. can.

Examples of this invention will be described below. In addition,
Although the following examples show only examples in which bulk polymerization and solution polymerization were applied as methods for synthesizing copolymers, the present invention is not limited to these examples.

Example 1 Methyl methacrylate 75g n-butyl acrylate 25g acrylic acid 15g azobisisobutyronitrile 0.1g lauryl mercaptan 0.05g 20g of the above composition was placed in a 500ml four-necked flask, and the mixture was stirred for 60 g. The atmosphere was replaced with nitrogen for a minute. Then, while dripping the remaining amount from the dropping funnel,
Reacted at 86℃ for 4.5 hours, weight average molecular weight 8.7×
A copolymer of 10 ⁵ (by GPC; calculated as styrene) was synthesized. This copolymer contained 13.5% by weight of unreacted unsaturated monomer.

Next, for the carboxyl group of this copolymer,
Add 1/8 equivalent of ammonia aqueous solution (25% by weight) to neutralize at a temperature of 83°C, and then add 150 parts by weight to 100 parts by weight of the copolymer while stirring.
Parts by weight of water were gradually added dropwise over a period of about 1.5 hours.
When 100 parts by weight of water was added dropwise, a phase inversion phenomenon occurred in which the continuous layer became water, and a stable slurry water dispersion was obtained.

The viscosity (25℃) of the slurry water dispersion thus obtained was 165 centipoise, and the solid content concentration was
It was 40% by weight. When the storage stability of this slurry water dispersion was investigated, no sedimentation or separation of copolymer particles was observed even after 14 days at 25°C. Also,
The above aqueous dispersion was cast onto a 50 μm thick polyester film and dried by heating at 120°C for 5 minutes to form a 50 μm thick polyester film.
A thick film was formed. The physical properties of this film are
When measured at 23° C. and a tensile rate of 50 mm/min, the film had an elastic modulus of 45 Kg/cm ² , an elongation of 1100%, and a bullet strength of 75 Kg/cm ² , indicating that it had excellent film properties.

Comparative Example A copolymer was synthesized with the same composition and under the same polymerization conditions as in Example 1. Freeze this copolymer at -10℃,
It was pulverized to obtain a fine powder of copolymer. This fine powder
100 parts by weight was gradually added to 150 parts by weight of ion-exchanged water, and the fine copolymer powder was dispersed in water at a rotation speed of 2000 rpm using a high-speed stirrer to obtain a slurry-like water dispersion. This dispersion had a markedly poor storage stability and was already precipitated and separated after 3 minutes. With such poor stability, it was difficult to form a film as in Example 1.

Example 2 Methyl methacrylate 65 g n-butyl acrylate 35 g Acrylic acid 0.5 g Azobisisobutyronitrile 0.1 g Lauryl mercaptan 0.05 g The same procedure as in Example 1 was carried out using the above polymerization raw materials, with a weight average molecular weight of 6.5 x 10 A copolymer of ⁵ was obtained.
The content of unreacted unsaturated monomers was 3.5% by weight. Next, an ammonia aqueous solution (25% concentration by weight) of 1 equivalent to the carboxyl group of this copolymer was prepared.
When 180 parts by weight of water is added to 100 parts by weight of the copolymer, a phase inversion occurs in which the continuous phase becomes water when 160 parts by weight of water is added. A phenomenon occurred, and finally a slurry-like water dispersion of the present invention was obtained.

The viscosity (at 25° C.) of this aqueous dispersion was 75 centipoise, and the solid content concentration was 35.7% by weight. Furthermore, when the storage stability was investigated, no sedimentation or separation of the copolymer particles was observed even after 14 days. The same results as in Example 1 were obtained regarding the film properties.

Example 3 Methyl methacrylate 85g n-butyl acrylate 15g acrylic acid 30g azobisisobutyronitrile 0.1g lauryl mercaptan 0.05g The same procedure as in Example 1 was carried out using the above polymerization raw materials, with a weight average molecular weight of 9.6×10 ⁵ A copolymer was obtained.
The content of unreacted unsaturated monomers was 21.8% by weight. Next, 1/36 equivalent of ammonia aqueous solution (25% by weight) was added to the carboxyl group of this copolymer to neutralize it, and the total amount was further adjusted to 70 parts by weight based on 100 parts by weight of the copolymer. When 40 parts by weight of water was added, a phase inversion phenomenon occurred in which the continuous phase became water, and finally the slurry-like water dispersion of the present invention was obtained.

The viscosity (at 25° C.) of this aqueous dispersion was 380 centipoise, and the solid content concentration was 58.8% by weight. Further, when the storage stability and film properties were examined, good results were obtained that were almost the same as those of Examples 1 and 2.

Example 4 n-butyl acrylate 30g ethyl acrylate 70g methacrylic acid 10g benzoyl peroxide 0.1g sec-butanol 5g Among the above polymerization raw materials, 10g of the monomer mixture and
5 g of sec-butanol was placed in a four-necked flask (No. 1), and the flask was purged with nitrogen at 40° C. for 40 minutes while stirring. Thereafter, 0.1 g of benzoyl peroxide was added and the temperature was raised to 80°C after completely dissolving it. Then add the remaining monomer mixture from the dropping funnel to approx.
Dropped at a rate of 0.87 g/min over 2 hours and heated to 83°C.
The reaction was allowed to proceed for 3.5 hours. The weight average molecular weight of the obtained copolymer was 6.2×10 ⁵ and the content of unreacted monomers was 9.0% by weight.

Next, 1/8 equivalent of ammonia was added to the carboxyl group of this copolymer to neutralize it at a temperature of 81°C, and then 120 parts by weight of water was added to 100 parts by weight of the copolymer. When 100 parts by weight of water was added, a phase inversion phenomenon occurred in which the continuous phase became water, and finally the slurry-like water dispersion of the present invention was obtained.

The slurry water dispersion thus obtained had a viscosity of 85 centipoise at 25° C. and a solid content concentration of 45.5% by weight. The storage stability and film properties of this aqueous dispersion were excellent and almost the same as those of Examples 1-3.

Claims (1)

[Claims] 1 0.1-35% by weight of unsaturated monomers having acidic groups
and other unsaturated monomers copolymerizable with it99.9-65
Weight average molecular weight obtained by copolymerizing with wt% 10 ⁴
~10 ⁶ copolymer and a small amount of unreacted unsaturated monomer used in the above copolymerization, and a raw material containing substantially no medium other than 0 to 20% by weight of an organic solvent. By adding an alkali or alkaline aqueous solution to neutralize some or all of the acidic groups in the copolymer molecules, and then further adding water and inverting the phase, the copolymer is dissolved in water. A method for producing a slurry water dispersion, the method comprising obtaining a stably dispersed slurry water dispersion.