JP2000103804A - Preparation of monodispersed minute particles, minute particles, and spacer for use in liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing monodispersed minute particles which can produce monodispersed minute particles suitable for seed particles for use in the seed polymerization of a polymer with a low mol.wt., having a uniform particle size and a high swell rate. SOLUTION: This is a method for preparing monodispersed minute particles, by dispersing a polymerizable unsatd. monomer, a polymerization initiator and a chain transfer agent in water, followed by a polymerization reaction by means of heating the dispersion wherein the chain transfer agent is an alkyl mercaptan type chain transfer agent with an n number of 1-10, and the chain transfer agent is added in an amt. 5-60 times as much as that of the polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing monodisperse fine particles, a method for producing fine particles by performing seed polymerization using the monodisperse fine particles obtained by the above method for producing monodisperse fine particles as seed particles, and The present invention relates to a method for producing a spacer for a liquid crystal display element, which performs seed polymerization using monodisperse fine particles obtained by the method for producing dispersed fine particles as seed particles.

[0002]

2. Description of the Related Art Polymer fine particles used for spacers for liquid crystal display elements, fillers for columns, carriers for diagnostic agents, and the like are:
It is required that the particle size be uniform. Conventionally, as a method of obtaining particles having a uniform particle size, there has been a method of classifying particles obtained by suspension polymerization. However, in this method, the yield of the obtained particles is low, and the uniformity of the particle diameter is not sufficiently satisfactory.

[0003] Also, a seed polymerization method has been proposed in which a vinyl-based monomer is absorbed into monodisperse fine particles such as a styrene-based polymer and then polymerized to increase the particle diameter. In this method, the particle diameter is 1 to 10 μm by repeating the process of absorbing and polymerizing the monomer in the fine polymer particles several times.
This is a method of obtaining fine particles of the order. However, in this method, there is a problem that the uniformity of the particle diameter of the generated fine particles is reduced, and the polymerization rate is also reduced.

Japanese Patent Publication No. 57-24369 and the like disclose 2
A method for obtaining a polymer having a uniform particle size by a stepwise swelling seed polymerization method is disclosed. In this method, a hydrophobic organic compound called a swelling aid is previously absorbed in seed particles,
This is a method of increasing the swelling ability of the seed particles and then swelling with a vinyl monomer to carry out polymerization. However, in this method, since the two absorption processes of absorption of the swelling aid and absorption of the monomer are repeated, the work becomes complicated, and further, the swelling aid not involved in the polymerization is eluted from the fine particles after the polymerization. There was a point.

[0005] In order to solve such a problem, utilizing the high swelling ability of the seed particles having a low degree of polymerization,
A method of obtaining particles of 1 to 10 μm in one step without using a swelling aid has been proposed. Also, Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open Publication No. H11-157, discloses a method in which a chain transfer agent is added at the time of emulsion polymerization to produce seed particles having a molecular weight of 10,000 or less to perform seed polymerization. However, just by adding a chain transfer agent,
Although the molecular weight is reduced, there is a problem that the particle size distribution tends to be widened.

[0006] Thus, by the seed polymerization of high swelling ratio,
In order to obtain particles having a particle size of 1 to 10 μm, it is optimal to use, as seed particles for seed polymerization, particles having a molecular weight of 20,000 or less and having a uniform particle diameter. It has not been established yet.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for producing monodisperse fine particles having a low molecular weight, a uniform particle diameter, and suitable for seed polymerization seed particles having a high swelling ratio. The purpose is to:

[0008]

According to the first aspect of the present invention, a polymerizable unsaturated monomer, a polymerization initiator and a chain transfer agent are dispersed in water,
A method for producing monodisperse fine particles in which a polymerization reaction is carried out by heating this dispersion liquid, wherein, as the chain transfer agent, an alkylmercaptan-based chain transfer agent having 1 to 10 carbon atoms is used, and the chain transfer agent is used. A method for producing monodisperse fine particles, characterized by adding 5 to 60 times the amount of the polymerization initiator. Hereinafter, the present invention will be described in detail.

In the method for producing monodisperse fine particles of the present invention 1, a polymerizable unsaturated monomer, a polymerization initiator and a chain transfer agent are dispersed in water, and the dispersion is heated to carry out a polymerization reaction. The polymerizable unsaturated monomer is not particularly limited as long as it is a monofunctional monomer that does not significantly dissolve in water. For example, styrene, α-methylstyrene, p-
Styrene derivatives such as methylstyrene, p-chlorostyrene and chloromethylstyrene; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl (meth) acrylate, (meth)
Ethyl acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate And (meth) acrylate derivatives such as cyclohexyl (meth) acrylate and methoxypolyethylene glycol (meth) acrylate. Of these, styrene derivatives are preferred.

The polymerization initiator is not particularly limited as long as it is generally used in emulsion polymerization, soap-free polymerization and the like, and includes, for example, potassium persulfate, azo-based initiator and the like.

In the present invention 1, an alkyl mercaptan chain transfer agent having 1 to 10 carbon atoms is used as the chain transfer agent. When the number of carbon atoms exceeds 10, the effect of chain transfer is reduced, and it may be necessary to add a large amount of a chain transfer agent to reduce the molecular weight to a desired molecular weight. The carbon number is preferably 6 to 10 since the workability is good due to low odor.

The alkyl mercaptan chain transfer agent is not particularly limited as long as it has a carbon number within the above range, and examples thereof include n-octyl mercaptan and n-decyl mercaptan.

The amount of the alkyl mercaptan chain transfer agent is 5 to 60 times the amount of the polymerization initiator. If the amount is less than 5 times, the effect of lowering the molecular weight may not be sufficient. If the amount is more than 60 times, the molecular weight may decrease but the number of oligomers may increase, so that the amount is limited to the above range. Preferably, it is 10 to 50 times, more preferably 15 to 40 times, even more preferably 20 to 30 times.

In the above-mentioned polymerization reaction, the above-mentioned dispersion is further added to:
It is preferable to carry out the polymerization reaction by adding an electrolyte. The electrolyte is not particularly limited, and examples thereof include sodium chloride and potassium chloride. The amount of the electrolyte added is 0.5 to 5 parts by weight based on 100 parts by weight of the polymerizable unsaturated monomer.
Parts by weight are preferred. If the amount exceeds 5 parts by weight,
The charge on the particle surface is canceled by the added electrolyte, and the aggregation tends to occur due to the instability, and the CV value of the particle diameter may be reduced. In some cases, the effect of adding electrolyte cannot be obtained.

The mixing ratio of the above polymerizable unsaturated monomer and water as a dispersion medium in performing the above polymerization reaction is not particularly limited, but from the viewpoint of yield and particle size distribution, the weight ratio is 5:95.
~ 20: 80 is preferred. If the amount of the polymerizable unsaturated monomer is less than 5% by weight, the yield relative to the charged amount may be extremely small, which is disadvantageous in production. If it exceeds 20% by weight, the particle size distribution is sufficiently controlled. May be difficult to obtain.

As a method for carrying out the above polymerization reaction, for example, water, a polymerizable unsaturated monomer, a chain transfer agent and a polymerization initiator are placed in a container, and then a nitrogen gas is poured thereinto to replace the polymerization atmosphere. A method of raising the temperature and the like can be given. In the above polymerization reaction, it is preferable to use a polymerization initiator dissolved in water. In addition, the temperature after the temperature is raised is not particularly limited, and may be appropriately selected depending on the type and concentration of the compound such as the polymerizable unsaturated monomer, the chain transfer agent, and the polymerization initiator to be used. ~ 90 ° C is preferred. The time for performing the above polymerization reaction is not particularly limited, and may be appropriately selected depending on the reaction conditions, and is usually preferably 12 to 36 hours.

The above polymerization reaction is soap-free polymerization, and the fine particles produced by the soap-free polymerization have a very narrow particle size distribution. In the above polymerization reaction, by adding a chain transfer agent, the molecular weight can be reduced without breaking the narrow particle size distribution width. Further, in the polymerization reaction, by adding an electrolyte, a stable state caused by the surface charge of the generated fine particles can be maintained, and therefore, fine particles having a narrower particle size distribution can be stably produced.

The monodispersed fine particles produced by the above polymerization reaction can be separated from the dispersion medium by centrifugation, and can be purified by repeatedly washing with alcohol and / or water. Further, after washing, the powder can be isolated as a powder by drying using a drying method such as spray drying or reduced pressure drying. According to the method for producing monodispersed fine particles of the first aspect of the present invention, monodispersed fine particles having a low average molecular weight of 20,000 or less and a uniform particle diameter can be produced. Further, the monodispersed fine particles obtained by the method for producing monodispersed fine particles can be suitably used as seed particles in seed polymerization having a high swelling ratio.

The present invention 2 provides a polymerizable unsaturated monomer in water,
A method for producing monodisperse fine particles in which a polymerization initiator and an electrolyte are dispersed and a polymerization reaction is performed by heating the dispersion, based on 100 parts by weight of the polymerizable unsaturated monomer.
A method for producing monodisperse fine particles, comprising adding 0.5 to 5 parts by weight of the electrolyte.

The polymerizable unsaturated monomer and the polymerization initiator are not particularly limited, and include the same as the polymerizable unsaturated monomer and the polymerization initiator of the present invention 1.

The electrolyte is not particularly limited, and examples thereof include sodium chloride and potassium chloride. The amount of the electrolyte to be added is 0.5 to 5 parts by weight based on 100 parts by weight of the polymerizable unsaturated monomer. When the addition amount exceeds 5 parts by weight, the charge on the particle surface is canceled by the added electrolyte, and the particles are likely to aggregate due to instability, and the CV value of the particle diameter may decrease, When the amount is less than 0.5 part by weight, the above-mentioned effect of the addition of the electrolyte may not be obtained in some cases.

The mixing ratio of the polymerizable unsaturated monomer and water as a dispersion medium in performing the above polymerization reaction is not particularly limited, and the same mixing ratio as that of the present invention 1 is preferable.
Examples of the method for performing the above polymerization reaction include the same method as the method of the first invention.

The above polymerization reaction is soap-free polymerization, and the polymerization reaction can also stably produce fine particles having a narrow particle size distribution. The monodispersed fine particles produced by the above polymerization reaction can be isolated as a powder by the same method as in the first aspect of the present invention.

According to the method for producing monodisperse fine particles of the present invention 2, monodisperse fine particles having a uniform particle diameter can be produced. Further, the monodispersed fine particles obtained by the method for producing monodispersed fine particles can be suitably used as seed particles in seed polymerization having a high swelling ratio.

Fine particles can be produced by performing seed polymerization using the monodisperse fine particles produced by the production methods of the present invention 1 and the present invention 2 as seed particles. The method for performing the seed polymerization is not particularly limited as long as the method uses monodispersed fine particles as seed particles, and a conventionally known method can be used. A method of dispersing monodispersed fine particles as water as seed particles in water, adding a finely dispersed emulsion of a polymerizable monomer and a polymerization initiator as an emulsion, absorbing the seed particles, polymerizing the particles, and synthesizing the fine particles. And the like. The method for producing fine particles using the above seed polymerization is also one of the present invention. In addition, the obtained fine particles can be applied to a column filler, a carrier for a diagnostic agent, and the like.

Further, the above monodisperse fine particles are used as seed particles,
By performing seed polymerization, a spacer for a liquid crystal display element can be manufactured. A method for producing a spacer for a liquid crystal display element using the above-mentioned seed polymerization is also one aspect of the present invention.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 10 parts by weight of styrene as a polymerizable monomer, 90 parts by weight of ion-exchanged water as a polymerization medium, and 2.5 parts by weight of n-octyl mercaptan as a chain transfer agent were mixed in a flask. Next, a cooling tube, a stirring blade, and a nitrogen introducing tube were attached to the container, and nitrogen was introduced thereinto for 1 hour to replace the polymerization atmosphere with nitrogen. Subsequently, the stirring blade was rotated at 180 rpm, the temperature was raised to 70 ° C., and the atmosphere was replaced with nitrogen for 1 hour. Thereafter, 0.1 parts by weight of potassium persulfate was dissolved in a small amount of water, and poured into the system using a syringe. Thereafter, the reaction was continued at 70 ° C. for 24 hours, and then the temperature was lowered to room temperature to stop the reaction. At the end of the reaction, the polymerization conversion was 80%. The resulting polymerization solution is centrifuged,
Solid-liquid separation of the polymerization medium and the fine particles was performed. Then, in order of ethanol, a mixed medium of ethanol and water, and water in this order,
Washing and centrifugation were performed each time, and an excessive polymerization initiator, monomer, and chain transfer agent were removed from the fine particles.

The washed fine particles were dispersed in an appropriate medium and deposited and fixed on a collodion film supported on a metal mesh.
This was observed using a transmission electron microscope. The particle diameters of 50 to 100 arbitrary particles in the photograph taken by this observation were measured, and the number average particle diameter (Dn) and weight average particle diameter (D
w) was determined. Further, as an index of particle size uniformity, D
w / Dn was also calculated. The results are shown in Table 1.

After the washed fine particles were isolated and dried, they were dissolved in tetrahydrofuran, and the molecular weight was measured by GPC. The results are shown in Table 1.

[0031]

[Table 1]

Example 2 Fine particles were obtained in the same manner as in Example 1 except that 2.0 parts by weight of n-decyl mercaptan was used instead of n-octyl mercaptan. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 Fine particles were obtained in the same manner as in Example 1 except that the amount of styrene was changed to 5 parts by weight and the amount of potassium persulfate was changed to 0.05 part by weight. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 Fine particles were obtained in the same manner as in Example 1 except that the amount of n-octyl mercaptan was changed to 0.5 part by weight. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 5 Fine particles were obtained in the same manner as in Example 1 except that 4.0 parts by weight of n-decyl mercaptan was used instead of n-octyl mercaptan. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 Fine particles were obtained in the same manner as in Example 1 except that no chain transfer agent was added. The particle diameter of the obtained fine particles, the uniformity of the particle diameter, and the weight average molecular weight were measured in the same manner as in Example 1,
The results are shown in Table 1.

Comparative Example 2 Fine particles were obtained in the same manner as in Example 1 except that the blending amount of n-octyl mercaptan was changed to 0.1 part by weight. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 Fine particles were obtained in the same manner as in Example 1, except that 1.0 part by weight of n-dodecyl mercaptan having 12 carbon atoms was used instead of n-octyl mercaptan. The particle size, particle size uniformity, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 6 Fine particles were obtained in the same manner as in Example 1 except that the chain transfer agent was not used and 0.02 parts by weight of sodium chloride was used. The particle size and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 1, and as an index of the particle size distribution, the CV value of the particle size was measured by the following method. The results are shown in Table 2.

Method for measuring CV value The following formula (1); CV value (%) = (σ / Dn) × 100 (1) (where σ represents the standard deviation of the particle diameter, Dn represents the number average particle diameter). The standard deviation is
Similar to the number average particle diameter, the particle diameter of 50 to 100 arbitrary particles was measured and calculated.

[0041]

[Table 2]

Example 7 Fine particles were obtained in the same manner as in Example 6 except that 1.5 parts by weight of n-octyl mercaptan was added and the amount of sodium chloride was changed to 0.1 part by weight. The particle diameter, CV value of particle diameter, and weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 6, and the results are shown in Table 2.

Example 8 Fine particles were obtained in the same manner as in Example 7, except that the amount of n-octyl mercaptan was changed to 2.5 parts by weight and the amount of sodium chloride was changed to 0.02 parts by weight. . The particle diameter, the CV value of the particle diameter, and the weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 6, and the results are shown in Table 2.

Example 9 Fine particles were obtained in the same manner as in Example 7 except that the amount of n-octyl mercaptan was changed to 0.5 part by weight. The particle diameter, the CV value of the particle diameter, and the weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 6, and the results are shown in Table 2.

Example 10 The amount of styrene was changed to 5.0 parts by weight, the amount of sodium chloride was changed to 0.2 parts by weight, and the amount of potassium persulfate was changed to 0.05 parts by weight. Fine particles were obtained in the same manner as in Example 7, except that 4.0 parts by weight of n-decyl mercaptan was used instead of n-octyl mercaptan. The particle diameter of the obtained fine particles, the CV value of the particle diameter, and
The weight average molecular weight was measured in the same manner as in Example 6, and the results were shown in Table 2.
It was shown to.

Comparative Example 4 Fine particles were obtained in the same manner as in Example 7, except that the amount of sodium chloride was changed to 3.0 parts by weight. The particle diameter, the CV value of the particle diameter, and the weight average molecular weight of the obtained fine particles were measured in the same manner as in Example 6, and the results are shown in Table 2.

[0047]

The method for producing monodisperse fine particles of the present invention 1
With the above configuration, it is possible to produce monodisperse fine particles having a low molecular weight and a uniform particle size, and having high swelling ratio and suitable for seed particles for seed polymerization. Since the method for producing monodisperse fine particles of the second aspect of the present invention has the above-described structure, monodisperse fine particles having a uniform particle diameter and suitable for seed particles for seed polymerization having a high swelling ratio can be produced. Further, since the method for producing fine particles of the present invention 1 and the present invention 2 has the above-described configuration, fine particles having a uniform particle diameter can be produced. Furthermore, since the method for manufacturing a spacer for a liquid crystal display element according to the first and second aspects of the present invention has the above-described configuration, a spacer for a liquid crystal display element having a uniform particle diameter can be manufactured.

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Claims (6)

[Claims] 1. A method for producing monodispersed fine particles, comprising dispersing a polymerizable unsaturated monomer, a polymerization initiator and a chain transfer agent in water, and heating the dispersion to carry out a polymerization reaction,
Monodisperse, wherein, as the chain transfer agent, an alkylmercaptan-based chain transfer agent having 1 to 10 carbon atoms is used, and the chain transfer agent is added in an amount of 5 to 60 times the amount of the polymerization initiator. A method for producing fine particles. 2. The method according to claim 1, wherein the chain transfer agent is an alkyl mercaptan-based chain transfer agent having 6 to 10 carbon atoms. 3. The method according to claim 1, wherein 0.5 to 5 parts by weight of an electrolyte is added to 100 parts by weight of the polymerizable unsaturated monomer. 4. A method for producing monodispersed fine particles, comprising dispersing a polymerizable unsaturated monomer, a polymerization initiator and an electrolyte in water, and heating the dispersion to carry out a polymerization reaction. A method for producing monodisperse fine particles, comprising adding 0.5 to 5 parts by weight of the electrolyte to 100 parts by weight of a saturated monomer. 5. A method for producing fine particles, comprising performing seed polymerization using the monodisperse fine particles obtained by the method for producing monodisperse fine particles according to claim 1, 2, 3 or 4 as seed particles. 6. A method for producing a spacer for a liquid crystal display element, comprising performing seed polymerization using the monodispersed fine particles obtained by the method for producing monodispersed fine particles according to claim 1, 2, 3 or 4 as seed particles. Method.