JPS6158495B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for producing a hydrosol made by stably dispersing a relatively high molecular weight polymer with an average particle size in the range of 0.01 to 0.1 μm in water, in particular, without using an emulsifier and without using any or almost no solvent. The present invention relates to a method for producing the above hydrosol. Conventionally, methods for producing hydrosols include polymer particles having carboxyl groups (particle size of approximately 0.3 ~
The so-called strippable method is generally adopted, in which the surface of particles (0.7 μm) is scraped off under high-speed stirring using an alkali such as caustic potash, caustic soda, or ammonium hydroxide to make fine particles with a particle size of approximately 0.01 to 0.1 μm. Ta. However, according to the above-mentioned conventional method, although the film-forming ability is improved due to fine particle formation, since the emulsifier is mixed into the hydrosol, the water resistance of the coating film and other molded products obtained therefrom deteriorates. Furthermore, there is a limit to the molecular weight of a polymer that can be converted into a hydrosol, and generally, when the weight average molecular weight is 10 ⁴ (10,000) or more, it becomes difficult to form a hydrosol. For this reason,
This naturally limits its application to various uses, and its applications have only been developed mainly in the paint field and paper size processing field. On the other hand, in the field of paints, a method of obtaining a hydrosol by adding an alkali and water to a solution polymer using a hydrophilic organic solvent and stirring and mixing the mixture without using the above-mentioned strippable method was proposed in the Japanese Patent Publication No. 52
This is proposed in Publication No. 47489, etc. According to this method, the water resistance of the paint film is improved because no emulsifier is used, but on the other hand, it uses a large amount of organic solvent, which poses problems in terms of environmental hygiene, pollution, and material cost. In addition, because polymerization uses a large amount of a hydrophilic organic solvent such as alcohol, the molecular weight of the polymer is low, making it difficult to apply it to applications such as adhesives and films that require high film properties. be. From the above viewpoint, the present invention provides a relatively high molecular weight polymer hydrosol which can be applied to adhesives, films, etc., and which can be produced without using an emulsifier or a large amount of organic solvent. The object of the present invention is to provide an industrially useful method for producing the hydrosol, and furthermore, to provide the above-mentioned method in which the resulting hydrosol is stable over time, and the stabilized hydrosol can be produced with good reproducibility. It is. That is, the present invention provides (A) a material having a weight average molecular weight of 10, consisting of 80 to 98% by weight of a main monomer mainly composed of acrylic ester or methacrylic ester and 20 to 2% by weight of a copolymerizable unsaturated monomer having an acidic group. The main component is an acrylic copolymer of ⁴ to 10 ⁶ , and the solvent content is 0 to 20 in the total amount of the above copolymer.
(B) a step of preparing raw materials in proportions of % by weight;
To the above raw material, add an alkali equivalent to at least 20% equivalent of the acidic group in the copolymer molecule and water in an amount of 100 to 400 parts by weight based on 100 parts by weight of the copolymer to form the copolymer molecule. A step of neutralizing some or all of the acidic groups in the copolymer and obtaining a hydrosol in which the copolymer is stably dispersed in water with an average particle size in the range of 0.01 to 0.1 μm, and
The process is divided into at least two stages, and the first stage is performed by: (a) adding an alkali equivalent to at least 15% of the acidic groups in the copolymer molecule to the raw material prepared in step A; 10 per 100 parts by weight of polymer
It consists of a step of adding a mixture with water at a ratio of ~40 parts by weight and stirring and mixing, and the second and subsequent steps are (b)
The stirred mixture of the previous step was further added with an alkali equivalent to at least 5% of the acidic groups in the above copolymer molecule, and the total amount of the amount required up to the previous step in the above proportion (based on 100 parts by weight of the above copolymer). The present invention relates to a method for producing a hydrosol, comprising a step of adding a mixture with water in an amount of 100 to 400 parts by weight and stirring and mixing. As described above, in this invention, first, in step A, a relatively high molecular weight copolymer containing no solvent or with a very small amount of solvent is prepared as a starting material, and this is used as a starting material in step B. One of the features of this method is that the high molecular weight copolymer used in step A of this method is limited to an acrylic copolymer having the above monomer composition. There is a significance. In other words, the above-mentioned acrylic copolymers are generally resins with low glass transition points (Tg), so they can be uniformly and stably processed during neutralization with alkali and water without requiring high shearing force even when the amount of solvent is small. Stirring mixing is possible, which has very good results for hydrosol stability and hydrosolization reproducibility. Another significance of this invention is that step B, which neutralizes the acrylic copolymer, is divided into at least two stages, and in step A of the first stage, the acidic groups in the copolymer molecules are Add the alkali necessary to neutralize the amount and a small amount of water and mix with stirring to obtain a stable water-containing composition that uniformly contains a small amount of water, which is used in the second and subsequent steps b. Add water and the required alkali instead of water alone and stir and mix.
This causes a phase inversion phenomenon between the oil phase and the aqueous phase to obtain the desired hydrosol. That is, the water-containing composition produced in step a above is either a transparent composition that uniformly absorbs water by neutralizing some of the acidic groups in the copolymer molecules, or It is a slightly white W/O type emulsion in which the copolymer is uniformly dispersed in the copolymer, and by forming such a water-containing composition, the viscosity of the copolymer is reduced and the viscosity of the copolymer is reduced. Neutralization in step b can be performed uniformly,
This greatly improves the reproducibility of hydrosolization and also improves the stability of the hydrosol produced. In addition, if water is added alone in the second and subsequent steps b, even if sufficient alkali is added in step a to neutralize the copolymer, water absorption and phase inversion will take a long time. This results in poor reproducibility of hydrosolization. The reason for this is that as the molecular weight of the copolymer increases, the acidic groups that should be neutralized become more difficult to neutralize due to steric factors such as being incorporated into the polymer chain. In systems where a large amount of This seems to be because the stability of the copolymer particles is impaired due to a decrease in the amount of copolymer particles. However, in this invention, since the step b from the second stage onwards is performed by adding a mixture of the required alkali and water and stirring and mixing, the copolymer is gradually neutralized by the alkali. This makes it possible to obtain a hydrosol with good reproducibility and stability without causing insufficient neutralization as described above. As described above, in this invention, a relatively high molecular weight acrylic copolymer is used as a starting material, and this is neutralized with a mixture of a small amount of water and the required alkali, and after this neutralization, further By adopting a specific multi-step neutralization method in which the required alkali and water are added and mixed with stirring, a hydrosol with good stability can be produced with good reproducibility. For example, you can add a mixture of water and alkali all at once to the above copolymer and stir and mix, or add only alkali to the above copolymer and neutralize it, then add water alone and stir. The above-mentioned effects cannot be obtained by methods such as mixing. The highly stable hydrosol obtained by the above-mentioned method of this invention does not use a large amount of solvent, so it does not cause problems in terms of environmental hygiene, and since it avoids contamination with emulsifiers, it can be used for coatings, etc. When molded into a molded product, it shows much improved water resistance compared to conventional hydrosols, and since the molecular weight of the acrylic copolymer is relatively high, various physical properties are also good, and compared to general organic hydrosols. It exhibits the same excellent performance as coatings formed from solvent solutions. Therefore, the hydrosol of the present invention has a wider range of applications than conventional hydrosols, and in addition to paints and paper sizing agents, it can also be used in adhesives, adhesives, overcoat materials, exterior materials, interior materials, packaging materials, etc. It can be extremely effectively applied to various fields such as film. In this invention, first, in Step A, 80 to 98% by weight of the main monomer mainly composed of acrylic ester or methacrylate is prepared by conventionally known methods such as solution polymerization, emulsion polymerization, pearl polymerization, and bulk polymerization. An acrylic copolymer with a weight average molecular weight of 10 ⁴ to 10 ⁶ consisting of a copolymerizable unsaturated monomer having an acidic group is synthesized, and the solvent content of this copolymer as the main component is 0 to 20% by weight. Prepare raw materials. In the bulk polymerization method and the solution polymerization method using 20% by weight or less of solvent, the reactant after polymerization can be used as the above raw material as it is, but in the case of ordinary solution polymerization method using a large amount of organic solvent, emulsion polymerization method and In the pearl polymerization method, the above raw material is prepared by removing the solvent and water as a polymerization medium by appropriate means after the polymerization reaction. In other words, in the solution polymerization method, by distillation,
In the emulsion polymerization method, the solvent or water is removed by salting out, and in the pearl polymerization method, the solvent or water is removed by filtration. In addition, in the emulsion polymerization method and pearl polymerization method, a portion of the emulsifier used during polymerization adheres to the surface of the polymer particles, but this emulsifier is removed together with the above removal operation, and can be removed by washing if necessary. do it. Furthermore, when unreacted monomer components are removed together during each of the above-mentioned removal operations, good results can be obtained in hydrosolization in the subsequent steps. From this point of view, even in bulk polymerization methods and solution polymerization methods using a small amount of solvent, it is desirable to perform a treatment such as distillation after polymerization to remove unreacted substances. The main monomers used in the synthesis of acrylic copolymers include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate,
isooctyl acrylate, ethyl methacrylate,
It is mainly composed of acrylic ester or ester methacrylate having an alkyl group having 2 to 15 carbon atoms, such as butyl methacrylate, and may also contain other monomers copolymerizable therewith. Examples of the other monomers include alkyl esters of acrylic acid or methacrylic acid in which the number of carbon atoms in the alkyl group is outside the above range, such as methyl acrylate and methyl methacrylate, vinyl acetate, acrylonitrile, styrene, 2-methoxyethyl acrylate,
In addition to vinyl ethers, various functional monomers such as glycidyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, acrylamide, and methylolacrylamide are widely included. These other monomers generally account for 50% by weight or less of the main monomers. Examples of copolymerizable unsaturated monomers having acidic groups used in combination with the above main monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid,
Unsaturated carboxylic acids with carboxyl groups as acidic groups such as maleic acid and fumaric acid, styrene sulfonic acid, allyl sulfonic acid, sulfopropyl acrylate, 2-acryloyloxynaphthalene-2-sulfonic acid, 2-methacryloyloxynaphthalene-2- Examples of acidic groups such as sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acryloyloxybenzenesulfonic acid include unsaturated sulfonic acids having a sulfonic group, and other acids having an acidic group. One or more of these may be used. The ratio of the main monomer to the copolymerizable unsaturated monomer having an acidic group should be 80 to 90% by weight for the former and 20 to 2% by weight for the latter, and particularly preferably 85 to 97% by weight for the former. %, and the latter is preferably 15 to 3% by weight. If the latter monomer is less than 2% by weight, it becomes difficult to form a hydrosol by alkali neutralization, whereas if it exceeds 20% by weight, the water resistance of the coating film etc. will be impaired, and both are unsuitable. The acrylic copolymer having the above monomer composition generally has a glass transition point of 0°C or lower, and its weight average molecular weight is set in the range of 10 ⁴ to 10 ⁶ , preferably 10 ⁵ to 10 ⁶ . It is necessary to be present. The reason for this is that if the molecular weight becomes too low, it will not be possible to improve the desired physical properties such as cohesive force and physical strength when used as a coating or other molded product, and if the molecular weight becomes too high, it will result in high viscosity. This is because it will interfere with the subsequent alkali treatment and make it difficult to generate a hydrosol. The solvent content is 20% by weight by the above method using an acrylic copolymer having such a molecular weight as the main component.
The raw material having the following properties and preferably from which unreacted substances have been removed is subjected to the next step B. Note that the above solvents include methanol, ethanol, n-
Propanol, isopropyl alcohol, Sec-
Preferably, it is an alcohol-based water-soluble solvent such as butanol. Step B of the present invention includes adding an alkali equivalent to at least 20% of the acidic group in the acrylic copolymer molecule to the raw materials and water in a proportion of 100 to 400 parts by weight based on 100 parts by weight of the copolymer. is added to neutralize some or all of the acidic groups in the copolymer molecules, and the copolymer has an average particle size of 0.01 to 0.1 μm.
This is a process for obtaining a hydrosol that is stably dispersed in the following range, and is particularly characterized in that this process is divided into at least two stages as follows. That is, first, in step a, the above raw materials are mixed with an alkali equivalent to at least 15% of the acidic group in the copolymer molecule and 10 to 10 parts by weight of the copolymer.
A mixture with 40 parts by weight of water is added and stirred to neutralize some of the acidic groups, thereby uniformly absorbing the small amount of water. Then, as step b, the remaining acidic groups are neutralized by gradually adding, under stirring, a mixture of an alkali equivalent to at least 5% of the acidic groups and the required water. In this step b, a phase inversion phenomenon occurs, and water becomes a continuous phase, producing an O/W type dispersion, that is, a hydrosol, in which copolymer particles are dispersed with an average particle size in the range of 0.01 to 0.1 μm. In step a above, if the amount of alkali used is less than 15% equivalent of the acidic group, the amount of neutralization will be insufficient and the hydrophilicity of the system will decrease, and even if water and alkali are added afterwards, they will not be absorbed and will separate. Put it away. Furthermore, if the amount of water exceeds 40 parts by weight, the alkali concentration will decrease and neutralization of acidic groups will be incomplete, resulting in the same problem as above.
On the other hand, if it is less than 10 parts by weight, it is not sufficient to uniformly permeate the alkali into the polymer, and neutralization becomes uneven, making it difficult to form a hydrosol with small particle size. In addition, in step b, an alkali necessary to neutralize some or all of the remaining acidic groups and water in an amount that provides an appropriate final solid content concentration (in the range of 20 to 50% by weight) are added. At this time, when water is added alone, the reproducibility of hydrosolization is poor and the stability of the generated hydrosol over time is poor, as described in detail above, so acidic groups in the copolymer molecules are It is necessary to use at least 5% equivalent of alkali. The amount of alkali is determined depending on the properties of the acrylic copolymer, the amount of acidic groups, etc., and when the amount of acidic groups is small, it is preferable to add an equivalent amount or more. However, if the amount is too large, it will adversely affect the film properties of the copolymer, so generally, the total amount of the alkali used in step a is 20% of the acidic group of the acrylic copolymer molecule.
Preferably, the proportion corresponds to ~200% equivalent. Note that this step b may be carried out in two or more stages if necessary, and in this case, the amount of alkali used in each stage is equivalent to at least 5% equivalent of the acidic groups of the copolymer. . The alkali concentration can be changed appropriately at each stage. For example, in the case of an acrylic copolymer with a small absolute amount of acidic groups, the acidic groups can be removed by dividing the copolymer into multiple stages in which the alkali concentration decreases from the previous step to the next step. It can be neutralized efficiently and good results can be obtained in hydrosolization. The temperature of the neutralization treatment consisting of steps a and b above is kept at a constant temperature depending on the type and properties of the acrylic copolymer, but in general
The temperature is 30-95℃. In addition, the alkali used in the above neutralization treatment includes ammonia, caustic soda, caustic alkali such as caustic potash, α-aminoethyl alcohol, ethylamine, propylene amine, etc., and the residual alkali in the paint film or film may have an adverse effect. In order to prevent this, it is preferable to use something that can be easily dispersed, such as ammonia or α-aminoethyl alcohol. The thus obtained hydrosol according to the present invention contains a finely divided acrylic copolymer with an average particle size of 0.01 to 0.1 μm, has excellent film-forming properties, and avoids contamination with emulsifiers. It exhibits much improved water resistance compared to conventional strippable types. Moreover, since no solvent is used or only a small amount is used, various problems associated with the use of solvents can be solved. Furthermore, since the molecular weight of the acrylic copolymer is relatively high, it has good physical properties and can be used for various purposes other than conventional hydrosols, such as adhesives, adhesives, films, and overcoat materials. can also be effectively applied, and all can exhibit excellent performance for these applications. EXAMPLES Below, examples of the present invention will be described in more detail. In the following, parts and % mean parts by weight and % by weight, respectively. Example 1 60 g of n-butyl acrylate 50 g of ethyl acrylate 15 g of methacrylic acid 0.1 g of azobisisobutyronitrile 0.09 g of lauryl mercaptan 15 g of the above composition was placed in a four-necked flask (No. 1) and stirred for 40 minutes. The atmosphere was replaced with nitrogen.
While dropping the remaining amount from the dropping funnel, the reaction was carried out at 85℃ for 4 hours, and the weight average molecular weight was 5×10 ⁵ (GPC
) was synthesized. Next, while stirring, 38 g of water containing 25% equivalent ammonia to the carboxyl group of the acrylic copolymer was added, and neutralization was carried out for 1 hour at a temperature of 80°C to absorb water sufficiently and uniformly. Then, while stirring, 375 g of water containing ammonia in an amount equivalent to 10% based on the carboxyl group was gradually added dropwise over a period of about 2 hours. When 120 g of water was dropped, a phase inversion phenomenon occurred in which the continuous layer became water. The hydrosol thus obtained is translucent, has a viscosity (at 25°C) of 280 poise, a solids concentration of 24.3%, and an average particle size of 0.04 μm (according to Nanosizer), and can be left at room temperature for one month. It remained stable with almost no change observed. Example 2 n-octyl acrylate 65 g Methyl methacrylate 35 g Acrylic acid 8 g Benzoyl peroxide 0.1 g sec-butanol 5 g Of the above composition, 10 g of the monomer mixture and sec
-butanol (5 g) was charged into a four-necked flask (No. 1), and the flask was purged with nitrogen at 40° C. for 40 minutes while stirring.
Then, 0.1 g of azobisisobutyronitrile was added, and after completely dissolving, the temperature was raised to 80°C. Then add the remaining monomer mixture through the addition funnel to approx.
Dropped at a rate of 0.87g/min over 2 hours, 85±5
Reacted at ℃ for 4 hours, weight average molecular weight 4×10 ⁵
A copolymer of (by GPC) was synthesized. Next, 6 for the carboxyl group of the copolymer.
% equivalent of α-aminoethyl alcohol 4.6g and water
Add a mixture of 25 g of α-aminoethyl alcohol and 200 g of water and neutralize at a temperature of 70 ± 5°C. It was dripped gradually.
When approximately 100 g of water was dropped, a phase inversion phenomenon occurred in which the continuous phase became water. The hydrosol thus obtained has a viscosity (at 25°C) of 470 poise and a solid content concentration of 34.9%.
The average particle diameter was 0.06 μm, and it remained stable without any change even after being left at room temperature for one month. Example 3 A monomer composition consisting of 75 g of 2-ethylhexyl acrylate, 20 g of ethyl acrylate, 3 g of 2-hydroxyethyl methacrylate, 3 g of methacrylic acid, 0.1 g of azobisisobutyronitrile, and 5 g of sec-butanol was polymerized in the same manner as in Example 2, Weight average molecular weight 3.5×10 ⁵ (by GPC)
A copolymer was synthesized. As a first step, 80% of the carboxyl groups in the copolymer are added to this copolymer.
Equivalent amounts of 1.7 g of α-aminoethyl alcohol and 15 g of water
After adding a mixture of g and thoroughly neutralizing it,
In the second step, a mixture of 1.1 g of α-aminoethyl alcohol and 100 g of water, equivalent to 50% relative to the carboxyl group, was gradually added dropwise. At this time, a phase inversion phenomenon was observed. Furthermore, as a third step, 30% equivalent of α-aminoethyl alcohol 0.6 to the carboxyl group
When a mixture of g and 115 g of water was added dropwise and stirring was continued, the liquid became more transparent and a stable hydrosol was obtained. The hydrosol thus obtained had a viscosity (at 25° C.) of 85 poise, a solids concentration of 29.6%, and an average particle size of 0.05 μm. Moreover, it remained stable with no change even after being left at room temperature for one month. Comparative Example 1 To a copolymer polymerized in exactly the same manner as in Example 2, 5.9 g of α-aminoethyl alcohol, equivalent to 80% of the carboxyl group, was added for neutralization, and then 225 g of water was gradually added. However, it took a long time to absorb the water without separating it. A phase inversion phenomenon occurred when approximately 70 g of water was added. The hydrosol thus obtained had an average particle diameter of 0.08 μm, a solid content concentration of 33.7%, and a viscosity (at 25° C.) of 410 poise. When this was left for one week at room temperature, it became milky white and a decrease in stability was observed. Comparative Example 2 To a copolymer polymerized in exactly the same manner as in Example 3, 3.4 g of α-aminoethyl alcohol equivalent to 160% of the carboxyl group was added for neutralization, and then 230 g of water was gradually added. When added, water approximately 90%
A phase inversion phenomenon occurred at the time of addition to g. The hydrosol thus obtained had an average particle diameter of 0.09 μm, a solid content concentration of 30.0%, and a viscosity (at 25° C.) of 60 poise. When this was left at room temperature for one week, separation of a small amount of water was observed. Comparative Example 3 A monomer mixture having the same composition as in Example 1 was mixed with thioglycolic acid as a chain transfer agent, potassium persulfate as a polymerization initiator, and hightenol as an emulsifier.
Emulsion polymerization was performed using N17 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) to obtain a polymer emulsion with a weight average molecular weight of 3×10 ⁵ . The hydrosols and emulsions obtained in Examples 1 to 3 and Comparative Example 3 were directly coated onto a glass plate using a coating rod, and 110
It was heated and dried at ℃ for 10 minutes to form a film with a thickness of 50 μm. All of these were excellent in film formation, and good films were obtained. The results of examining the water resistance and other properties of this film are shown in the table below.

[Table] As shown in the above table, according to the present invention, a relatively high molecular weight polymer can be made into a stable hydrosol in the form of fine particles. Moreover, as is clear from the above test results, the hydrosol obtained by the method of this invention can form a film with excellent water resistance, and since it is a high molecular weight substance, the mechanical properties of the film are also fully satisfactory. It turns out that it is possible.

Claims (1)

[Claims] 1 (A) 80 to 98% by weight of main monomers mainly consisting of acrylic esters or methacrylic esters
Copolymerizable unsaturated monomer with acidic group 20~
2% by weight of an acrylic copolymer with a weight average molecular weight of 10 ⁴ to 10 ⁶ as the main component, and the solvent content is 0 to 20% by weight based on the total amount of the above copolymer. (B) adding an alkali equivalent to at least 20% of the acidic groups in the copolymer molecule to the raw material and water in an amount of 100 to 400 parts by weight based on 100 parts by weight of the copolymer; In addition, it includes the step of neutralizing some or all of the acidic groups in the copolymer molecules and obtaining a hydrosol in which the copolymer is stably dispersed in water with an average particle size in the range of 0.01 to 0.1 μm. , and the step B is divided into at least two stages, and the first step is performed by: (a) adding to the raw material prepared in step A an amount equivalent to at least 15% of the acidic groups in the copolymer molecules; 10 to 100 parts by weight of alkali and the above copolymer
It consists of a step of adding a mixture with 40 parts by weight of water and stirring and mixing, and (b) adding the acidic groups in the copolymer molecules to the stirred mixture of the previous step. The total amount of alkali equivalent to at least 5% equivalent and the amount required up to the previous step is in the above ratio (100 to 100 parts by weight per 100 parts by weight of the above copolymer).
A method for producing a hydrosol, comprising the step of adding and stirring and mixing a mixture with water in an amount of 400 parts by weight.