JP5436833B2 - Polymer fine particles and method for producing the same - Google Patents

Description

  The present invention relates to polymer fine particles having a narrow particle size distribution, and particularly relates to polymer fine particles which are excellent in heat resistance, safe and have a small content of fine particles having a specific size or less.

Polymer fine particles having a narrow particle size distribution are anti-blocking agents for resin films, optical resin materials that impart light diffusibility and antireflection antiglare properties to various display devices, spacers for liquid crystals, additives for toners for developing electrostatic images, Powder paint and water dispersion type paint, additive for decorative plate, additive for artificial marble, filler for cosmetics, column filler for chromatography, light diffusing agent, abrasive, etc. for electrical and electronic materials, optical materials, This material is expected to be applied in various fields such as chemical products. As a typical one used in these applications, a polymer obtained by radical polymerization of a radical polymerizable monomer component using 2,2′-azobisisobutyronitrile (AIBN) as a polymerization initiator Fine particles are known (Patent Documents 1 to 3).
JP-A-8-183807 Japanese Patent Laid-Open No. 10-7730 JP 2002-293809 A Japanese Laid-Open Patent Publication No. 1-443504

  However, since AIBN, which is a polymerization initiator, produces harmful decomposition products as a by-product during the polymerization reaction, the polymer fine particles produced by the conventional method contain the decomposition products of AIBN as impurities. Therefore, although the polymer fine particles obtained by the above conventional method are suitably used as various additives other than food applications, the use of such fine particles in food applications is not possible due to the toxicity of the degradation products of AIBN. In the food packaging field, there is a need for fine particles that do not use AIBN.

  There is also a method for producing polymer fine particles using a polymerization initiator other than AIBN (for example, an azo polymerization initiator other than AIBN, an organic peroxide, or the like) (Patent Document 4). However, polymer fine particles obtained when an azo polymerization initiator (for example, dimethyl-2,2′-azobis (2-methylpropionate)) is used are finer particles than when AIBN is used. The thermal decomposition temperature of is low. Therefore, when producing a film using the fine particles, a thermoplastic resin is usually used as the resin for the film. Therefore, the polymer fine particles are decomposed by being exposed to a high temperature in the process of processing the resin into a film. Or discoloration, which adversely affects the appearance (coloring and transparency) of the film.

  Further, the present inventors may cause polymer particles produced using the polymer particles to have cloudiness even if the particle size distribution is narrow. In such a case, the particle size distribution It was found that the figure contains particles of minute size that do not appear easily.

  The present invention has been made paying attention to the circumstances as described above, and the purpose thereof is excellent in safety and heat resistance, and further, the particle size distribution is narrow and the inclusion of particles having a minute size below a specific size. An object of the present invention is to provide polymer fine particles having a reduced amount and a method for producing the same.

The polymer fine particles of the present invention that can solve the above problems have a thermal decomposition starting temperature of 310 ° C. or higher, and a volume-based most frequent particle diameter (dw) of 0.1 μm to 20 μm,
The ratio dn / dw of the number-based most frequent particle diameter (dn) to the volume-based most frequent particle diameter is 0.45 or more, and the tetramethylsuccinonitrile content is 100 ppm or less in the polymer fine particles. However, it has characteristics.

  The polymer fine particles of the present invention having the above structure not only have a narrow particle size distribution but also a low content of fine particles having a specific size or less, and also have high heat resistance and are contained in the polymer fine particles. In addition, since the content of the toxic decomposition product derived from the polymerization initiator is suppressed, defects derived from fine particles and the decomposition product, such as coloring and decomposition, are unlikely to occur.

  The polymer fine particles are at least one selected from the group consisting of hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, lactone antioxidants, thiol compounds, and components derived therefrom. It is preferable to contain a seed, and more preferable is to contain a hindered phenol antioxidant and / or a component derived therefrom, and a thiol compound and / or a component derived therefrom.

  The present invention also includes a method for producing the above-mentioned polymer fine particles. The production method is a production method of the above-mentioned polymer fine particles, which is 100 parts by mass of a radical polymerizable monomer, 0.1 part by mass to 10 parts by mass of a non-nitrile-azo radical polymerization initiator, and an antioxidant. A monomer composition containing 0.05 part by mass to 5 parts by mass and / or 0.05 part by mass to 10 parts by mass of a thiol-based compound is radically polymerized.

  The thiol compound is desirably a polyfunctional thiol compound having a molecular weight of 200 or more. Moreover, in the said manufacturing method, it is recommended to use a hindered phenolic antioxidant as antioxidant.

  The polymer fine particles of the present invention are excellent in heat resistance and not only have a narrow particle size distribution but also have a reduced content of fine particles. Therefore, it is also suitable for applications that require higher precision control regarding particle size distribution. For example, even when used for optical materials such as displays and film applications, defects caused by fine particles such as haze are unlikely to occur. . In addition, since the polymer fine particles of the present invention contain little or no toxic decomposition products (by-products) derived from specific polymerization initiators, they can be used in a wide range of fields including medical and food fields. Can be used. Furthermore, since it is also excellent in heat resistance, it is difficult to cause deterioration of polymer fine particles and poor molded products (coloring, etc.) even when exposed to high temperatures after mixing with other resins. .

  The polymer fine particles of the present invention having the above-described structure are an antiblocking agent for resin films, an optical resin material that imparts light diffusibility and antireflection antiglare properties to various display devices, a spacer for liquid crystal, and an electrostatic image developing toner Additives, powder paints and water dispersion type paints, decorative plate additives, artificial marble additives, cosmetic fillers, chromatography column fillers, light diffusing agents, abrasives, etc. It can be applied to various fields such as optical materials and chemical products. In particular, it is suitably used as various additives such as anti-blocking agents for food packaging materials.

  The polymer fine particle of the present invention has a thermal decomposition starting temperature of 310 ° C. or higher, a volume-based most frequent particle diameter (dw) of 0.1 μm to 20 μm, and is based on the number basis for the volume-based most frequent particle diameter. The ratio dn / dw of the most frequent particle diameter (dn) is 0.45 or more, and the tetramethylsuccinonitrile content is 100 ppm or less in the polymer fine particles.

  In view of the above-mentioned problems of the prior art, the present inventors had no problem of toxicity derived from the decomposition product of AIBN, and have repeatedly investigated polymer fine particles having excellent heat resistance. When a specific polymerization initiator is used, in addition to containing no harmful decomposition products, not only a narrow particle size distribution but also a reduced content of fine particles less than a specific size. It was found that coalesced fine particles were obtained, and the present invention was completed. Hereinafter, the present invention will be described in detail.

  The thermal decomposition start temperature of the polymer fine particles of the present invention is 310 ° C. or higher. When the thermal decomposition start temperature is less than 310 ° C., when the fine particles are mixed with the softened and melted resin, the fine particles are decomposed, and the characteristics derived from the polymer fine particles cannot be obtained. There is a risk of voids and the like. More preferably, it is 320 degreeC or more, More preferably, it is 330 degreeC or more.

  In the present invention, using a thermal analyzer (for example, DTG-50M manufactured by Shimadzu Corporation), polymer fine particles are thermally decomposed under the conditions described in the examples described later, and obtained at this time. The intersection of the baseline of the TG curve and the tangent of the sudden mass reduction portion is defined as the thermal decomposition start temperature (tangential intersection method).

  The polymer fine particles of the present invention have a volume-based most frequent particle diameter (dw) of 0.1 μm to 20 μm. More preferably, they are 0.3 micrometer-10 micrometers, More preferably, they are 0.5 micrometer-5 micrometers. Moreover, the most frequent particle diameter (dn) based on a preferable number is 0.1 μm to 20 μm, more preferably 0.3 μm to 10 μm, and further preferably 0.4 μm to 2 μm.

  In the polymer fine particles of the present invention, the ratio dn / dw of the number-based most frequent particle diameter (dn) to the volume-based most frequent particle diameter is 0.45 or more. This requirement means that the polymer fine particles of the present invention have a small content of fine particles whose particle diameter is less than a specific size with respect to the average particle diameter (volume basis). As described above, the present inventors may include fine particles having a small particle distribution even if the polymer particles are considered to have a narrow particle distribution. And the light scattering (diffusion) characteristics are significantly affected. Therefore, when we reexamined why such a phenomenon occurs, there is a reason that the particle size distribution is usually shown on a volume basis (weight basis) when confirming the particle size distribution of particles. I found. In other words, when the particle size distribution is expressed on a volume basis, the volume of the data constituting each section is weighted, so that a large particle size is represented with a large frequency, and a small particle with a small particle size is represented by There is a tendency that it is difficult to be reflected in the particle size distribution map. Therefore, when polymer fine particles are used with reference to the particle size distribution expressed on a volume basis, problems derived from fine particles (for example, problems such as poor transparency and light scattering characteristics in optical materials) It happened unexpectedly.

  Therefore, the present inventors decided to adopt a number-based particle size distribution that can accurately grasp the abundance of fine particles in addition to the volume-based particle size distribution. The content of fine particles can be determined by the ratio dn / dw of the number-based most frequent particle diameter (dn) to (dw), and in particular, when dn / dw is 0.45 or more, It has been found that the content is relatively low. Therefore, in the present invention, dn / dw is used as a criterion for determining the content of fine particles.

  The ratio dn / dw of the number-based most frequent particle diameter (dn) to the volume-based most frequent particle diameter (dw) is more preferably 0.5 or more, and further preferably 0.55 or more. On the other hand, the upper limit is preferably 1, more preferably 0.8 or less. When dn / dw is less than 0.45, the content of fine particles is large, and the transparency and light diffusibility of the molded product are deteriorated due to the influence of the fine particles.

  In the present invention, the fine particles are particles having a particle diameter of 50% or less of the most frequent particle diameter in the volume-based particle size distribution in a particle diameter range measurable when measured by a centrifugal sedimentation method. Means. Then, this value is applied as it is to a particle size distribution diagram based on the number, and the content of particles having the particle size is defined as the amount of fine particles contained in the polymer fine particles. That is, if the most frequent particle size in the volume-based particle size distribution is 1 μm, the particle size criterion determined as a fine particle is 0.5 μm (1 μm × 0.5). The amount of particles having a particle size of 0.5 μm or less is the amount of fine particles.

  The smaller the content of such fine particles in the polymer fine particles, the better. Preferably it is 45% or less, More preferably, it is 43% or less, More preferably, it is 40% or less.

  In the present invention, the volume-based most frequent particle diameter (dw) and the number-based most frequent particle diameter (dn) are measured using a centrifugal sedimentation type particle size distribution measuring apparatus (for example, “DC12000” manufactured by CPS Instruments). The measured value is used, and the volume and number-based particle size distribution created based on the measured value is used. It should be noted that measured values are used for data necessary for the measurement, for example, the true specific gravity of the particles, the refractive index at the measurement temperature, the refractive index of the solvent, and the viscosity. In the above measurement, the most frequent particle size (volume basis, number basis) is a value obtained by a centrifugal sedimentation type particle size distribution measuring device with 0.3 μm as the lower limit of measurement.

  Although the conditions at the time of measurement are not particularly limited, for example, the measurement temperature is preferably 10 ° C to 40 ° C, more preferably 10 ° C to 35 ° C.

  The polymer fine particles of the present invention also have a feature that the content of tetramethylsuccinonitrile is 100 ppm or less in the polymer fine particles.

  As described above, conventionally, azobisisobutyronitrile (AIBN) is generally used as a polymerization initiator when performing radical polymerization using a vinyl compound as a monomer component. However, since decomposition products derived from a polymerization initiator having a nitrile group and an azo group, such as AIBN, are toxic, if the decomposition product is contained in the polymer particles, the use of the polymer particles May be limited. Accordingly, the content of such harmful decomposition products is preferably as small as possible. In the polymer fine particles of the present invention, tetramethylsuccinonitrile is the most desirable decomposition product for which the content is desired to be reduced.

  The content of tetramethylsuccinonitrile in the polymer fine particles of the present invention is 100 ppm or less, preferably 50 ppm or less, more preferably 20 ppm or less. Polymer fine particles not containing the decomposition product (that is, content 0%) are the most preferred embodiment of the present invention.

  The tetramethyl succinonitrile is mainly known as a decomposition product of 2,2′-azobisisobutyronitrile. In the present invention, in addition to the tetramethyl succinonitrile, the following general formula is used. It is also recommended to reduce the content of other decomposition products having the structures (I) and (II) represented by the formula in the polymer fine particles.

  The content of the decomposition products (other decomposition products) having the structures of the above general formulas (I) and (II) in the polymer fine particles is preferably 100 ppm or less. In addition, although the above-mentioned tetramethyl succinonitrile is contained in the decomposition product which has the structure of the said general formula (I), in this invention, the structure of the said general formula (I) except tetramethyl succinonitrile is included. It is desirable that the content of the decomposition product having a content of 100 ppm or less. When the above-mentioned other decomposition products are contained in the polymer fine particles (one or more decomposition products having the structure of the general formula (I) and / or one or more decomposition products having the structure of the general formula (II)) The content of these decomposition products is preferably 100 ppm or less. For example, when two kinds of decomposition products having the structure of the general formula (I) are included, the content of each is preferably 100 ppm or less. More preferably, the total amount of one or more decomposition products having the structure of the general formula (I) excluding tetramethylsuccinonitrile and one or more decomposition products having the structure of the general formula (II) is 100 ppm or less. More preferably, the total content of tetrasuccinomethylnitrile and the other decomposition products is 100 ppm or less.

  In addition, it is more preferable that the upper limit of the amount of each other decomposition product and the total content of two or more kinds of other decomposition products is 50 ppm, and a more preferable upper limit is 20 ppm.

  In the present invention, the decomposition product for which the content in the polymer fine particles is preferably limited is not particularly limited as long as it has the structure of the above general formula (I) or (II) in the molecule. Such a decomposition product can be generated when a nitrile-azo polymerization initiator having a nitrile group and an azo group in the molecule is used. Examples of the nitrile-azo polymerization initiator that can produce a decomposition product having the structure of the general formula (I) include polymerization initiators having the structure of the following general formula (III).

  Examples of the polymerization initiator having the structure of the general formula (III) include 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) and 2,2′-azobis (2,4-dimethyl). Valeronitrile), 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 4,4 ′ A polymerization initiator such as azobis (4-cyanopentanoic acid), 4,4′-azobis (4-cyanopentanoic acid) -α, ω-diaminopropyl poly (dimethylsiloxane) copolymer, 4,4′-azobis ( And macroazo polymerization initiators such as 4-cyanopentanoic acid) -polyethylene glycol copolymer. On the other hand, 2- (carbamoylazo) isobutyronitrile is mentioned as a nitrile-azo polymerization initiator which can produce | generate the decomposition product which has the structure of the said general formula (II). That is, in the present invention, it is desirable that the content of decomposition products derived from these polymerization initiators is 100 ppm or less.

  The polymer fine particles of the present invention preferably contain an antioxidant and / or a component derived from an antioxidant and / or a thiol compound and / or a component derived therefrom. When the polymer fine particle contains a component derived from an antioxidant or a thiol compound, the heat resistance of the polymer fine particle can be improved, and the initial color tone (b value) of the polymer fine particle is low, and The change in color tone before and after the heating of the polymer fine particles (difference in b value before and after the heat resistance test) is small.

  Examples of the antioxidant include hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, lactone antioxidants, hydroxylamine antioxidants, and vitamin E antioxidants. It is done. The hindered phenol-based antioxidant means one having a para-substituted 2,6-di-tert-butylphenol structure in the structure of the antioxidant, and the sulfur-based antioxidant is a sulfur element. And a phosphorus-based antioxidant means a compound containing a phosphorus atom in its structure, and a lactone-based antioxidant means a compound having a cyclic ester structure. These structures may contain two or more types at the same time, and in this case, in this specification, each antioxidant is classified mainly according to the portion exhibiting the antioxidant effect.

  Specific examples of the hindered phenol-based antioxidant include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5- Di-tert-butyl-1-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], benzene Propanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy, C7-C9 side chain alkyl ester, 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert -Butyl-a, a ', a' '-(mesitylene-2,4,6-tolyl) tri-p-cresol, calcium diethylbis [[[3,5-bis (1 1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate], ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine -2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tris [(4-tert-butyl-3-hydroxy-2,6-xylyl) methyl] -1,3,5- Triazine-2,4,6 (1H, 3H, 5H) -trione, the reaction product of N-phenylbenzenamine and 2,4,4-trimethylbenzene, diethyl [[3, -Bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate, 2,4-dimethyl-6- (1-methylpentadecyl) phenol, octadecyl-3- (3,5-tert-butyl- 4-hydroxyphenyl) propionate, 2 ′, 3-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] propionohydrazide and the like are raised.

  As the sulfur-based antioxidant, thiodiethylene bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 4,6-bis (dodecylthiomethyl) -o-cresol, 4, 6-bis (octylthiomethyl) -o-cresol, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol and the like; Examples thereof include a thioether compound (1) having a structural unit represented by the following formula (IV) having a thioether bond (C—S—C).

In formula (IV), n means an integer of 1 to 5 (preferably n = 2).

  Among the thioether compounds (1), compounds having two or more structural units represented by the above formula (IV) in the molecule are preferable. More preferably, it is a compound having 2 to 4 structural units represented by the above formula (IV) in the molecule, and particularly preferred are 4 structural units represented by the above formula (IV) in the molecule. It is a compound that has.

  Among the thioether compounds (1), a thioether compound (2) having a structural unit represented by the following formula (V) is preferable. More preferable as the thioether compound (2) is a compound having 2 to 4 structural units represented by the following formula (V) in the molecule, and more preferably a structural unit represented by the following formula (V). It is a compound having four.

Here, n is an integer of 1 to 5 (preferably n = 2), R ¹ is at least one group selected from the group consisting of an alkyl group, an aryl group, an aralkyl group, and an alkenyl group, and R ¹ May have a substituent.

  The alkyl group is preferably an alkyl group having 1 to 20 carbon atoms, more preferably 3 to 20, still more preferably 6 to 18 and particularly preferably 12 to 18 carbon atoms because it has a high effect of improving heat resistance. It is an alkyl group. Examples thereof include alkyl groups such as propyl group, butyl group, pentyl group, hexyl group, octyl group, dodecyl group (lauryl group), tridecyl group, myristyl group, octadecyl group (stearyl group) and the like.

  Examples of the aryl group include a phenyl group, a hydroxyphenyl group, a tolyl group, and an o-xylyl group. Among these, a phenyl group and a hydroxyphenyl group are preferable.

  Examples of the aralkyl group include a benzyl group, a methylbenzyl group, a phenethyl group, a methylphenethyl group, a phenylbenzyl group, and a naphthylmethyl group. Examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, a 1-butenyl group, Examples include 2-butenyl group.

  Among these, an alkyl group and an aryl group are preferable, and an alkyl group having 12 to 18 carbon atoms is particularly preferable.

Examples of the substituent that R ¹ has include a hydroxyl group, an amino group, a carboxyl group, an alkyl group, an aryl group, an aralkyl group, and an alkenyl group.

  Preferred examples of the thioether compound (2) having four structural units represented by the above formula (V) include a pentaerythrityl tetrakis (3-alkylthiopropionate) compound. Specifically, pentaerythrityl tetrakis (3-methylthiopropionate), pentaerythrityl tetrakis (3-ethylthiopropionate), pentaerythrityl tetrakis (3-propylthiopropionate), pentaerythrityl tetrakis (3-butylthiopropionate), pentaerythrityltetrakis (3-hexylthiopropionate), pentaerythrityltetrakis (3-octylthiopropionate), pentaerythrityltetrakis (3-laurylthiopropionate) ), Pentaerythrityltetrakis (3-tridecylthiopropionate), pentaerythrityltetrakis (3-myristylthiopropionate), pentaerythrityltetrakis (3-stearylthiopropionate), pentaerythritol Such Rutetorakisu (3-phenyl thiopropionate) are exemplified. Among them, those having an alkyl group having 3 to 20 carbon atoms are preferable, more preferably a compound having 6 to 18 carbon atoms in the alkyl group, and particularly preferably a compound having 12 to 18 carbon atoms in the alkyl group.

  In particular, pentaerythrityl tetrakis (3-laurylthiopropionate) having an alkyl group having 12 carbon atoms is preferable because it can be obtained at low cost.

  As the thioether compound (1), a thioether compound (3) having a structural unit represented by the following formula (VI) is also preferably used as the sulfur antioxidant according to the present invention.

In formula (VI), n is an integer of 1 to 5 (preferably n = 2).

  Among the thioether compounds (3) having the structural unit represented by the above formula (VI), the thioether compounds having the structural unit represented by the following formula (VII) are more preferable.

n is an integer of 1 to 5 (preferably n = 2).

In formula (VII), R ² and R ³ are each independently at least one group selected from the group consisting of an alkyl group, an aryl group, an aralkyl group, and an alkenyl group, and R ² and R ³ May have a substituent. In addition, as an alkyl group, an aryl group, an aralkyl group, and an alkenyl group, the thing similar to the case of R < ¹ > in the said thioether type compound (2) can be illustrated preferably. R ² and R ³ are preferably an alkyl group or an aryl group, and particularly preferably an alkyl group.

  Examples of the substituent include an alkyl group, an aryl group, an aralkyl group, an alkenyl group, a hydroxyl group, an amino group, and a carboxyl group.

  Preferred examples of the thioether compound (3) having a structural unit represented by the formula (VII) include a dialkyl-3,3'-thiodipropionate compound. Specifically, dimethyl-3,3′-thiodipropionate, diethyl-3,3′-thiodipropionate, dipropyl-3,3′-thiodipropionate, dibutyl-3,3′-thiodiprote Pionate, dihexyl-3,3′-thiodipropionate, dioctyl-3,3′-thiodipropionate, didodecyl-3,3′-thiodipropionate (dilauryl-3,3′-thiodipropionate ), Dimyristyl-3,3′-thiodipropionate, ditridecyl-3,3′-thiodipropionate, dioctadecyl-3,3′-thiodipropionate (distearyl-3,3′-thiodipropionate) Nate) and the like. Among these, those having an alkyl group having 3 to 20 carbon atoms are preferable, compounds having 6 to 18 carbon atoms in the alkyl group are more preferable, and compounds having 12 to 18 carbon atoms in the alkyl group are more preferable.

  Particularly, didodecyl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, ditridecyl-3,3′-thiodipropionate, dioctadecyl having an alkyl group having 12 to 18 carbon atoms. -3,3'-thiodipropionate is preferred because it is easily available industrially.

  Examples of phosphorus antioxidants include tris (2,4-di-tert-butylphenyl) phosphite, tris [2-[[2,4,8,10-tetra-tert-butyldibenzo [d, f] [ 1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis [2,4-bis (1 , 1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, etc. Is mentioned.

  Examples of the lactone antioxidant include a reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene (CAS No. 181314-48-7), and the like. Examples of hydroxylamine antioxidants include oxidation products of alkylamines from reduced beef tallow, and vitamin E antioxidants include 3,4-dihydro-2,5,7,8-tetramethyl-2. -(4,8,12-trimethyltridecyl) -2H-benzopyran-6-ol and the like. These antioxidants may be used alone or in combination of two or more.

  Among the above antioxidants, it is preferably at least one selected from the group consisting of hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, and lactone antioxidants, and more preferably. It is a hindered phenol antioxidant. In particular, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] is used as a hindered phenol-based antioxidant, and tetrakis [methylene-3] is used as a sulfur-based antioxidant. -(Dodecylthio) propionate] methane (pentaerythrityltetrakis (3-laurylthiopropionate)) is preferred, and tris (2,4-di-tert-butylphenyl) phosphite is preferred as the phosphorus antioxidant. .

  The antioxidant and / or the component derived therefrom is preferably contained in the polymer fine particles according to the present invention in an amount of about 10 ppm or more, more preferably 15 ppm or more, further preferably 50 ppm or more, More preferably, it is 100 ppm or more, particularly preferably 200 ppm or more and 500 ppm or more, still more preferably 0.1% or more. When there is too little content of antioxidant, the effect of a heat resistant improvement may be difficult to be acquired. Although an upper limit is not specifically limited, It is preferable that it is 5% or less, More preferably, it is 3% or less, More preferably, it is 1% or less. In addition, when the polymer microparticles | fine-particles which concern on this invention contain 2 or more types of antioxidant, it is preferable that the sum total of the content exists in the range of the said content.

  The content of the antioxidant in the polymer fine particles according to the present invention will be described in detail in Examples below. For example, after the polymer fine particles are dissolved in a suitable solvent, or from the polymer fine particles to the antioxidant. Extracted into a solvent, and then analyzed by high-performance liquid column chromatography (for example, “NANOSPACE SI-2” manufactured by Shiseido Co., Ltd.), from a standard solution calibration curve prepared in advance using only an antioxidant. The antioxidant content in the polymer fine particles can be calculated.

  The polymer fine particles of the present invention preferably contain a thiol compound and / or a component derived from a thiol compound. A thiol-based compound has a thiol group (-SH) in the molecule, and this thiol-based compound binds to the end of the polymer chain that repeats the polymerization reaction, thereby stabilizing the polymer chain and suppressing depolymerization. Therefore, heat resistance is improved.

  Therefore, examples of the existence form of the thiol compound in the polymer fine particles include a form in which the thiol-based compound is present by being bonded to the carbon atom at the end of the polymer chain constituting the polymer fine particle by an S—C bond.

  By the way, the sulfur-based antioxidant has a sulfur atom in the molecule like the thiol-based compound, but the sulfur-based antioxidant exists as a sulfur-based antioxidant in the polymer fine particles. Yes. However, the sulfur-based antioxidant is difficult to form a bond with the polymer chain constituting the polymer fine particles. Therefore, the presence form of the thiol-based compound and the sulfur-based antioxidant in the polymer fine particles is different.

  The sulfur-based antioxidants are partially oxidized during the polymerization reaction, sulfonated, or exist in some presumed intermediate structures having radical scavenging ability. It is thought that what has contributes to the improvement in heat resistance. However, from the viewpoint of the contribution to improving the heat resistance of the polymer fine particles, it is preferably present in the polymer fine particles in the form of a sulfur-based antioxidant. This is because the sulfur-based antioxidant itself has a higher radical scavenging ability than that having an intermediate structure that has already undergone decomposition, and an excellent heat resistance improvement effect can be obtained. On the other hand, as described above, the thiol-based compound is preferably present in the polymer fine particle in combination with the polymer chain constituting the polymer fine particle, that is, as a component derived from the thiol-based compound.

  The thiol-based compound may have a functional group other than the thiol group. Examples of the other functional group include carbon such as carboxyl group, phenyl group, methyl group, ethyl group, propyl group, and butyl group. Examples thereof include an alkyl group of 1 to 20. The thiol-based compound may have a single functional group among the other functional groups described above, or may have a different type of functional group. It may have a plurality of groups.

  As the thiol-based compound that can be used in the present invention, a polyfunctional and high molecular weight thiol having a plurality of thiol groups and the above-mentioned other functional groups and having a molecular weight of 200 or more, preferably 500 to 5000 is preferable. When the thiol compound is monofunctional and the molecular weight is less than the above range, a low molecular weight polymer is likely to be formed. The molecular weight is more preferably 800 to 2500, and even more preferably 1000 to 1500. Since a low molecular weight polymer is likely to be eluted from polymer fine particles, for example, such an elution component may be a problem in a film or the like used for packaging food or medical products. Examples of the polyfunctional and high molecular weight thiol compounds include pentaerythritol tetrakisthioglycolate (PETG), trimethylolpropane tristhioglycolate (TMTG), butanediol bisthioglycolate (BDTG), ethylene glycol bisthioglycolate ( EGTG) and the like.

  As described above, the polymer fine particles according to the present invention preferably contain sulfur element in the form of a sulfur-based antioxidant and / or a component derived therefrom, a thiol-based compound and / or a component derived therefrom. . More preferably, the polymer fine particles contain sulfur element in the form of a component derived from a sulfur-based oxide or thiol-based compound (that is, a form in which the thiol-based compound is incorporated in the molecular chain constituting the polymer fine particle). It is a waste.

  In addition, the content of elemental sulfur in the polymer fine particles is preferably 1 ppm or more in terms of the amount of sulfur atoms. More preferably, it is 10 ppm or more, More preferably, it is 55 ppm or more, Especially preferably, it is 110 pm or more, It is preferable that it is 5500 ppm or less, More preferably, it is 3300 ppm or less, Especially preferably, it is 1100 ppm or less. Moreover, as a preferable range, it is preferable that it is 10-5500 ppm, More preferably, it is 55-3300 ppm, More preferably, it is 110-1100 ppm.

  When the polymer fine particles contain only a sulfur-based antioxidant, the amount of sulfur atoms derived from the sulfur-based antioxidant is preferably within the above-mentioned range, while only the thiol-based compound is contained in the polymer fine particles. The amount of sulfur atoms derived from the thiol-based compound incorporated in the molecular chain constituting the polymer fine particle is preferably within the above range, and the sulfur-based antioxidant and the component derived from the thiol-based compound are both If included, the total amount of both is preferably in the above range.

  Note that the content of sulfur element can be analyzed by, for example, inductively coupled plasma emission spectroscopy (ICP) or mass spectrometry.

  Examples of the presence of the component derived from the antioxidant and / or thiol compound in the polymer fine particles of the present invention include FIGS. These are diagrams schematically showing the embodiment of the polymer fine particles of the present invention. FIG. 1A shows an embodiment in which an antioxidant is attached to the surface of the polymer fine particles (first embodiment), FIG. (B) shows an embodiment in which a layer containing an antioxidant is present in the vicinity of the surface of the polymer fine particles (second embodiment), and FIG. 1 (c) shows that the antioxidant is contained in the entire interior of the polymer fine particles. The aspect (3rd aspect) which has disperse | distributed is shown. In order to prevent segregation of characteristics and to make organic polymer fine particles exhibiting excellent heat resistance as a whole, the third aspect in which an antioxidant is dispersed inside the polymer fine particles is preferable. . Such polymer fine particles are obtained by cutting the fine particles and analyzing the cut surface with an analyzer capable of element mapping (for example, an X-ray microanalyzer (EPMA) or the like). This can be confirmed by observing the state. In any of the embodiments shown in FIGS. 1A to 1C, the component derived from the thiol-based compound is present bound to the polymer chain constituting the polymer fine particle.

  The polymer fine particles of the first aspect are obtained by mixing polymer fine particles (either dry fine particles or fine particle dispersion) obtained by polymerization and an antioxidant (which may be powdery or liquid). The polymer fine particles of the second aspect having an antioxidant layer on the surface are obtained by oxidizing the fine particle dispersion after polymerization or by dissolving or dispersing the produced polymer fine particles in an appropriate solvent. It is obtained by dipping in an inhibitor solution and impregnating the surface layer portion of the polymer fine particles with an antioxidant. Furthermore, the polymer fine particles of the third aspect in which the antioxidant is dispersed inside the polymer fine particles are obtained by a method of performing a polymerization reaction in the presence of the antioxidant (details will be described later). Of the three modes, the second and third modes are preferable, and the third mode is particularly preferable because the effect of using a sulfur-based antioxidant is high.

  As the monomer component constituting the polymer fine particles of the present invention, any of (meth) acrylic monomers and monomers copolymerizable with the (meth) acrylic monomers can be used.

  Examples of the (meth) acrylic monomer include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, and tetrahydro acrylate. Furfuryl, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, etc. However, it is not limited to these. These (meth) acrylic monomers may be used alone or in combination of two or more. In addition, it is preferable that the polymer fine particles according to the present invention contain the (meth) acrylic monomer as a main component, and specifically, those containing 50 to 100% by mass of the (meth) acrylic monomer. Preferably, it is recommended that 60 to 100% by mass of the (meth) acrylic monomer is used.

  Moreover, you may use the crosslinkable (meth) acrylic-type monomer which has a several polymerizable double bond group in a molecule | numerator as a monomer copolymerizable with the above-mentioned (meth) acrylic-type monomer. By using such a monomer component, polymer fine particles having a crosslinked structure between molecules can be obtained. Examples of such crosslinkable (meth) acrylic monomers include trimethylolpropane triacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, decaethylene glycol dimethacrylate, and pentamethacrylate. (Meta) such as decaethylene glycol, pentamethaethylene diacrylate, ethylene glycol, 1,3-butylene dimethacrylate, allyl methacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, diethylene glycol dimethacrylate An acrylic monomer is mentioned.

  Furthermore, as a monomer copolymerizable with the above-mentioned (meth) acrylic monomer, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butyl Styrene monomers such as styrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof, N, N-divinyl Cross-linking agents such as aniline, divinyl ether, divinyl sulfide, divinyl sulfonic acid, etc., polybutadiene, and JP-B-57-56507, JP-A-59-221304, JP-A-59-221305, JP-A-59-221306 Gazette, JP-A-59-22130 It may be used such as a reactive polymer as described in JP-like.

  As the monomer component copolymerizable with the (meth) acrylic monomer, one kind may be used alone, or a plurality may be used in combination.

  In addition, the polymer fine particles of the present invention containing an antioxidant preferably have an initial b value of −1.0 to 3. More preferably, it is -0.5-1.5, More preferably, it is -0.3-1.0. Here, the b value indicates that the larger the value is, the more polymer fine particles are yellowish, and the smaller the value (negative value), the more bluish, and the b value is near 0. Shows that it is colorless. The initial b value indicates the hue of the polymer fine particles immediately after production, that is, the polymer fine particles of the present invention having the initial b value in the above range have a color tone almost infinitely colorless. It can be said.

  The b value means a b value among L, a, and b measured by a color difference meter. For example, b value is calculated | required by measuring the reflected light in the powder state of polymer fine particles using the spectroscopic color difference meter "SE2000" by Nippon Denshoku Industries Co., Ltd.

  The polymer fine particles according to the present invention preferably have a b value change amount (Δb) of 1.0 or less before and after being heated at 100 ° C. for 1 hour in an air atmosphere. More preferably, it is 0.5 or less, More preferably, it is 0.1 or less, Especially preferably, it is 0.05 or less. A smaller value of Δb indicates that there is less change in the hue of the polymer fine particles after heating.

  Next, the method for producing polymer fine particles of the present invention will be described.

  As described above, the polymer fine particles of the present invention can be produced by various methods (first aspect, second aspect, and third aspect). Among these, polymerization is performed in the presence of an antioxidant. It is preferably obtained by the method for carrying out the reaction (third aspect). That is, the production method of the present invention is a method characterized by radical polymerization of monomer components in the presence of an antioxidant. In this way, if the polymerization reaction is allowed to proceed in the presence of an antioxidant, the antioxidant is incorporated into the resulting polymer, so that the segregation of the antioxidant is unlikely to occur, and oxidation is prevented in the resulting polymer fine particles. Polymer fine particles having excellent heat resistance are obtained by dispersing the agent.

  In addition, since an antioxidant has an effect of scavenging radicals, an antioxidant is not usually used in radical polymerization using free (free) radicals as a driving force for the polymerization reaction. This is because the presence of an antioxidant in the reaction system makes it difficult for the polymerization reaction to proceed and the polymerization rate decreases. Therefore, radical polymerization in the presence of an antioxidant is the greatest difference between the present invention and the prior art.

  In the method of the present invention, any known polymerization method such as emulsion polymerization, suspension polymerization or seed polymerization can be employed. Among these, the suspension polymerization method and the seed polymerization method are preferable. A solvent may be used during the polymerization reaction, for example, water; alcohols such as methanol, ethanol, isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate Organic solvents such as the like can be used.

  In general, suspension polymerization is carried out by polymerizing a droplet suspension composition obtained by dispersing and suspending a monomer composition comprising monomer components in water. This is a method of obtaining a dispersion liquid in which coalesced fine particles are dispersed and contained in water.

  When preparing the droplet suspension composition, conventionally known dispersion, suspension methods, and apparatuses can be employed as means for suspending the monomer composition in water. For example, T.W. K. A high-speed stirrer such as a homomixer or a line mixer (for example, Ebara Milder (registered trademark)) can be used.

  Further, in order to control and stabilize the particle diameter of the droplets of the monomer composition, it is preferable that a dispersion stabilizer described later is coexisted when preparing the droplet suspension composition. In preparing the fine particles of the third aspect “an aspect in which the antioxidant is contained in the fine particles”, it is preferable to disperse and dissolve the antioxidant in the monomer composition.

  The polymerization initiator (described later) may be present in the suspension composition at the time of the polymerization reaction, but is dispersed and dissolved in the monomer composition phase or the aqueous phase at the time of preparing the droplet suspension composition. In particular, an embodiment in which the monomer composition is dissolved in advance is preferable. The polymerization reaction is preferably performed with stirring. For the stirring, stirring using a conventionally known stirring blade such as a paddle blade, a turbine blade, a blue margin blade, or a propeller blade may be employed.

Therefore, the suspension polymerization preferably comprises the following steps.
(1) a step of preparing a monomer composition by dispersing and dissolving a polymerization initiator and an antioxidant in a monomer component;
(2) a step of preparing a droplet suspension composition by suspending the monomer composition in water obtained by dispersing and dissolving a dispersion stabilizer (used as necessary);
(3) A polymerization reaction of the droplet suspension composition is started (by heating or the like), the droplet monomer composition is polymerized, and a dispersion liquid in which polymer fine particles are dispersed and contained in water is obtained. Preparing step.

  As the antioxidant, those described above are used. However, since the production method of the present invention involves radical polymerization of the monomer component described above in the presence of the antioxidant, It is preferably one that dissolves in the monomer component or the polymerization solvent. The blending amount of the antioxidant is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the monomer component. More preferably, they are 0.1 mass part-3 mass parts, More preferably, they are 0.5 mass part-2 mass parts. In addition, when using 1 type of antioxidant independently, when using 2 or more types of antioxidant, it is preferable to set it as the range of the said compounding quantity.

  In the method of the present invention, the antioxidant and / or thiol compound is used. The antioxidant and the thiol compound may be used alone or in combination. The thiol-based compound contributes to improving the heat resistance of the polymer fine particles. As the thiol-based compound, those described above can be used, and the amount used is preferably 0.05 to 10 parts by weight, more preferably 100 parts by weight of the polymerizable monomer component. 1 part by mass to 5 parts by mass. The timing of adding the thiol-based compound is not particularly limited, and may be mixed with the monomer component or the polymerization initiator in advance before the start of polymerization. You may add in a polymerization system. In addition, from the viewpoint of maximizing the effect of the addition of the thiol compound, it is preferable to mix and use a monomer component, a polymerization initiator, and the like in advance.

  In addition, also when using together an antioxidant and a thiol type compound, it is preferable that these usage-amount is also in the said range.

  In the present invention, a non-nitrile-azo initiator that has an azo group in the molecule but has no nitrile group is used as the polymerization initiator. Non-nitrile-azo initiators include, for example, dimethyl 2,2′-azobis (2-methylpropionate), 2,2′-azobis (2,4,4′-trimethylpentane), 2,2 ′. -Azobis (2-methylpropionamidooxime), 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2'-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2,2′-azobis {2-methyl-N- [2-hydroxyethyl) propionamide]}, 2,2′- Azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide), 2,2'-azobis (N-cyclohex Ru-2-methylpropionamide), 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazoline) -2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [2- (3,4) , 5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl) propane] dihydrochloride 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis (2-methylpropionamidine) dihydrochloride, , 2'-azobis [N-(2-carboxyethyl) -2-methyl - propionamidine], and the like. Among these, it is recommended to use dimethyl 2,2′-azobis (2-methylpropionate) and 2,2′-azobis (2,4,4′-trimethylpentane), which are highly soluble in organic solvents. Is done. Since these polymerization initiators do not have a nitrile group and an azo group in the molecule at the same time, they produce tetramethylsuccinonitrile and decomposition products having the structures shown in the above formulas (I) and (II). It is hard to do.

  As described above, the compounds having the structures represented by the above formulas (I) and (II) are derived from a polymerization initiator having an azo group and a nitrile group in the molecule. Therefore, in the present invention, it is preferable not to use a nitrile-azo polymerization initiator having an azo group and a nitrile group in the molecule. Specific nitrile-azo polymerization initiators include those represented by the above formula (III). Among them, 2,2′-azobisisobutyronitrile is recommended to be avoided. Is mentioned.

  The amount of the non-nitrile-azo polymerization initiator used is preferably 0.1 parts by mass to 10 parts by mass, more preferably 0.3 parts by mass to 100 parts by mass of the polymerizable monomer component. 5 parts by mass, and more preferably 0.5 to 3 parts by mass.

  The polymerization temperature is preferably 60 ° C to 100 ° C, more preferably 65 ° C to 95 ° C, and further preferably 70 ° C to 90 ° C. The polymerization reaction is preferably 2 hours to 7 hours, more preferably 2.5 hours to 5 hours, and even more preferably 3 hours to 4.5 hours. Moreover, it is preferable to perform a polymerization reaction in the range of pH 4-10.

  Further, at the time of the polymerization reaction, a dispersion stabilizer may be used in order to proceed the polymerization reaction stably. Examples of the dispersion stabilizer include water-soluble polymers such as polyvinyl alcohol, gelatin, tragacanth, starch, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, sodium polyacrylate, and sodium polymethacrylate; anionic surfactants; cationic surfactants Zwitterionic surfactant; nonionic surfactant; other alginate, zein, casein, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, diatomaceous earth, bentonite, titanium hydroxide, Thorium hydroxide, metal oxide powder, etc. are used.

  Examples of the anionic surfactant include fatty acid salts such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfonic acid. Salt, alkane sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl sulfate, and the like.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene- Examples include oxypropylene block polymers.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride. Examples of the zwitterionic surfactant include lauryl dimethylamine oxide.

  What is necessary is just to adjust the usage-amount of the said dispersion stabilizer suitably according to the size of the desired polymer fine particle. For example, if it is desired to obtain polymer fine particles having a particle size of 0.1 μm to 20 μm, 0.01 parts by mass to 10 parts by mass, more preferably 0.05 parts by mass to 100 parts by mass of the monomer component. 5 parts by mass, more preferably 1 part by mass to 2 parts by mass is recommended.

  In addition to the antioxidant and the dispersion stabilizer, various additives may be used as necessary. Specific examples include pigments, plasticizers, polymerization stabilizers, fluorescent brighteners, magnetic powders, ultraviolet absorbers, antistatic agents, and flame retardants.

  On the other hand, the seed polymerization method is an embodiment of an emulsion polymerization method. After producing seed particles that are precursors of polymer fine particles, the seed particles absorb a polymerizable monomer component, In this method, polymer components are polymerized to obtain polymer fine particles. The seed polymerization method has an advantage that the degree of polymerization of the polymer fine particles and the particle diameter can be controlled more easily than other polymerization methods. Further, the physical properties of the polymer fine particles can be controlled by changing the monomer component composition between the monomer component constituting the seed particle and the monomer component absorbed by the seed particle.

  When the seed polymerization method is adopted, the timing of addition of the antioxidant and the thiol compound may be any of the seed particle production stage and the polymerizable monomer component absorption stage. From the viewpoint of effectively exhibiting the effect of the system compound, it is preferable to absorb the antioxidant and the thiol system compound in the seed particles simultaneously with the monomer component at the absorption stage of the polymerizable monomer component. For example, it is more preferable that the seed particles absorb a monomer composition containing a monomer component, an antioxidant, a thiol compound, and a polymerization initiator.

  As in the case of the suspension polymerization method, the amount of the antioxidant is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass with respect to the total amount of monomer components (100 parts by mass). It is above, More preferably, it is 0.5 mass part or more, Preferably it is 5 mass parts or less, More preferably, it is 3 mass parts or less, More preferably, it is 2 mass parts or less.

  The blending amount of the thiol compound is also preferably 0.05 parts by mass to 10 parts by mass, more preferably 1 part by mass to 10 parts by mass with respect to the total amount of the monomer components, as in the case of the suspension polymerization method. It is.

  The antioxidant and the thiol compound may be used alone or in combination, and the blending amount is preferably within the above range.

  Seed particles are obtained by dispersing and polymerizing monomer components in a reaction solvent containing water and an emulsifier. As the monomer component, any of the above-mentioned (meth) acrylic monomers and styrene monomers and monomers copolymerizable therewith can be used.

  The above-mentioned various surfactants can be used as the emulsifier, and among them, anionic surfactants and nonionic surfactants are preferably used. The amount of the emulsifier used may be appropriately selected depending on the type of monomer component and the desired particle size, but is usually 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the monomer component used as a raw material for seed particles. It is preferred to be parts by mass. More preferably, it is 0.05 mass% or more, More preferably, it is 0.5 mass part or more, It is more preferable to set it as 8 mass parts or less, More preferably, it is 5 mass% or less.

  As the polymerization initiator, a non-nitrile-azo polymerization initiator is used as in the case of the suspension polymerization method. The amount used is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the monomer component. More preferably, it is 0.3-5 mass parts, More preferably, it is 0.5-3 mass parts.

  The reaction temperature during the production of seed particles is preferably 20 ° C to 70 ° C. The particle diameter of the seed particles may be appropriately determined according to the use of the polymer fine particles, but is preferably 0.1 μm to 5 μm.

  Next, a polymerizable monomer component (preferably a monomer composition containing a monomer component, an antioxidant and / or a thiol compound and a polymerization initiator) is absorbed into the obtained seed particles ( Absorption process). The composition of the monomer component used at this time may be the same as that of the seed particles, or may be changed according to a desired application and physical properties. The monomer component is a seed particle suspension in a pre-emulsion (monomer dispersion) obtained by emulsifying the monomer composition in a reaction solvent (preferably water) using an emulsifier. It is preferable to add to.

  As an emulsifier, the same thing as what was used by manufacture of seed particles is mentioned, and a compounding quantity shall be 0.01 mass part-10 mass parts with respect to 100 mass parts of monomer ingredients contained in a pre emulsion. Is preferred. More preferably, it is 0.05 mass part-8 mass parts, More preferably, it is 0.5 mass part-5 mass parts. Moreover, as a polymerization initiator, the same thing as the case of suspension polymerization can be used. The amount of the polymerization initiator used is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the monomer component contained in the pre-emulsion. More preferably, it is 0.1 mass part-10 mass parts, More preferably, it is 0.5 mass part-5 mass parts.

  It is preferable to perform an absorption process at 0 to 70 degreeC, More preferably, it is 15 to 40 degreeC.

  After confirming that the seed particles have absorbed a monomer component (preferably a monomer composition containing a monomer component, an antioxidant and a polymerization initiator), the polymerizable monomer in the seed particles Is polymerized (polymerization step). The absorption of the polymerizable monomer can be confirmed by observing the particle diameter of the seed particles before and after the absorption step with a microscope. That is, if the particle diameter after completion of the absorption process is larger than the particle diameter before the absorption process starts, it can be determined that the monomer component is absorbed in the seed particles.

  The method for initiating the polymerization reaction is not particularly limited. For example, polymerization is performed by generating radicals in the polymerization reaction system by a method using a radical polymerization initiator, a method of irradiating ultraviolet rays or radiation, a method of applying heat, or the like. And a method of radical polymerization of the polymerizable monomer component. These methods may be used in combination.

  The reaction conditions (temperature, time, pH) in the polymerization step can be the same as in the suspension polymerization method. Moreover, you may use various additives as needed.

  The fine polymer particles produced by the radical polymerization reaction may be subjected to a process such as drying and, if necessary, classification. In addition, it is preferable to perform drying at 180 degrees C or less, More preferably, it is 150 degrees C or less, More preferably, it is 120 degrees C or less. A box-type dryer or the like can be used as the dryer. The oxygen concentration during drying is preferably 10% by volume or less. More preferably, it is 5 volume% or less, More preferably, it is 2 volume% or less.

  The polymer fine particles of the present invention obtained by carrying out a polymerization reaction in the presence of an antioxidant and / or a thiol compound using the specific polymerization initiator described above are only excellent in heat resistance. In addition, the initial b value is low, and the color tone does not easily change over time. Furthermore, in addition to providing safety, the content of fine particles having a specific size or less is also reduced. Therefore, the polymer fine particles of the present invention are used in various applications, for example, a light diffusing sheet or light guide plate used for LCDs, or a light diffusing agent or anti-blocking agent contained in an optical resin used for PDP, EL display and touch panel. It is also suitable for optical applications such as additives such as agents, antiblocking agents for various films, lubricants, and the like.

  Next, the case where the polymer fine particles of the present invention are used for the above applications will be described. When the polymer fine particles of the present invention are used as additives for various applications, the polymer fine particles of the present invention are preferably used as a resin composition mixed with other components such as a binder resin.

  The amount of polymer fine particles contained in the resin composition may be appropriately determined according to the use of the resin composition and desired properties, but is usually used for optical use such as a light diffusion plate (described below). Aspect (I)) is preferably 0.01 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin. More preferably, it is 0.05 mass part or more, More preferably, it is 0.1 mass part or more, More preferably, it is 10 mass part or less, More preferably, it is 5 mass part or less. Moreover, if it is a case where it uses as a light-diffusion sheet obtained by coating the coating liquid containing the said resin composition on base materials, such as a film (the aspect of the following (II)), with respect to 100 mass parts of binder resin. The amount is preferably 5 parts by mass or more and 600 parts by mass or less. More preferably, it is 10 to 500 mass parts, More preferably, it is 20 to 400 mass parts. When the content of the polymer fine particles is too large, the strength of the molded product obtained by using this resin composition may be reduced. On the other hand, when the content is too small, the polymer fine particles may be obtained by using the polymer fine particles. It may be difficult to obtain an effect (such as light diffusibility).

  The transparent binder resin contained in the resin composition is not particularly limited, and any of those used as a binder resin in this field can be used. For example, (I) When the member formed using the resin composition of the present invention is formed by molding the resin composition itself into a plate shape, a sheet shape or the like (binder resin, plate shape, sheet A base resin of a molded article), polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins, polystyrene resins, polyether sulfone resins, polyurethane resins, polycarbonate resins, Polyolefin resins such as polysulfone resins, polyether resins, polymethylpentene resins, polyether ketone resins, (meth) acrylonitrile resins, polypropylene resins, norbornene resins, amorphous polyolefin resins, polyamide resins , Polyimide resin, and triacetyl cellulose Resin etc. are mentioned.

  In addition, (II) a member to be molded is formed by laminating (coating, laminating, etc.) the resin composition of the present invention on a previously prepared plate-like or sheet-like substrate surface. In some cases, examples of the binder resin include acrylic resins, polypropylene resins, polyvinyl alcohol resins, polyvinyl acetate resins, polystyrene resins, polycarbonate resins, fluororesins, silicone resins, and polyurethane resins.

  In addition to the polymer fine particles and the transparent binder resin, the resin composition of the present invention may contain other components as necessary as long as the effects of the present invention are not impaired. Examples of other components include various additives such as an ultraviolet absorber for enhancing physical properties such as light resistance and UV resistance, a crosslinking agent, a fluorescent whitening agent, and a flame retardant. These may use only 1 type and may use 2 or more types together.

  As described above, since the polymer fine particles of the present invention are excellent in heat resistance and have a reduced content of fine particles, deterioration due to heating is also caused when a molded product is produced from the above resin composition. In addition, since the polymer fine particles of the present invention are dispersed and fixed in the transparent binder (or base material) resin, coloring based on thermal discoloration of the fine particles is suppressed, and the color is colorless. It has excellent transparency and light diffusibility, and can exhibit excellent optical properties such as high brightness and high transparency. Therefore, in an image display device, it is also suitably used for optical members such as a light diffusion sheet (film) and a light diffusion plate that uniformly diffuse light from a light source on the image display surface. In addition, the shape of the molded body is not limited to a sheet shape (film shape) or a plate shape, and may be a molded body such as a column, a cone, or a sphere.

  For example, when the molded body obtained from the resin composition according to the present invention is a sheet (film) -like molded body such as a light diffusion sheet (film), the form has a planar portion, and a binder. The form which has at least one part the structure by which polymer fine particles are fixed by resin is mentioned. For example, (i) a resin composition itself, a plate-like or sheet-shaped form (light diffusion plate), (ii) a plate-like or sheet-like base material surface prepared in advance or in part, The form (light diffusion sheet) etc. which laminated | stacked and integrated the layer which consists of the said resin composition are mentioned. In both cases (i) and (ii), the polymer fine particles of the present invention are dispersed and fixed in the transparent binder resin, so that excellent optical properties can be exhibited.

  The above-mentioned “having a planar portion” generally means a substantially flat surface portion having a certain area spread such that the shape of the optical member is a plate shape, a sheet shape or a film shape. However, in the present invention, the present invention is not limited to such a mode, and even if it is not the main component, a substantially flat surface portion is provided on at least a part of the shape. It only has to have.

  As a method for producing a molded article of the above form (i), the above resin composition is extruded while melting and kneading with a known extruder, and is in the form of a plate (thickness: 1 mm or more) or sheet (thickness: 200 μm). To less than 1 mm) and a film (thickness: 1 μm to less than 200 μm). Moreover, the molded object shape | molded in the film form can also be extended | stretched to a uniaxial or biaxial direction using a conventionally well-known extending | stretching apparatus, and it can also shape | mold into a thin film-like stretched film (thickness: 5 micrometers-100 micrometers). . At this time, in order to enhance physical properties such as light resistance and UV resistance, additives such as various additives, stabilizers and flame retardants may be added to the resin composition as necessary. In order to obtain a molded article having uniform optical properties, the resin composition is preferably mixed and dispersed in advance with the polymer fine particles of the present invention in a binder resin. Similarly, the additive may be mixed with the resin composition.

  Examples of the method for obtaining the molded article having the form (ii) include a method of laminating a layer made of the resin composition on a previously prepared base material surface. The lamination method is not particularly limited, and the resin composition is mixed with an organic solvent (for example, alcohols such as methanol, ethanol and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as toluene and xylene; ethyl acetate). Such as polyesters such as polyethylene terephthalate and polyethylene naphthalate; triacetyl cellulose; olefin polymers such as cyclopolyolefin and amorphous polyolefin; polymethyl methacrylate (Meth) acrylate resin-based polymers such as (meth) acrylate having a lactone ring structure; polystyrene resin; polycarbonate resin, etc.) (coating method, casting method, etc.). Specific coating methods include known laminating methods such as reverse roll coating, gravure coating, die coating, comma coating, and spray coating.

  Moreover, after laminating | stacking the said resin composition on the base-material surface, it is good also as a stretched film by extending | stretching the base material on which the resin composition was laminated | stacked to the uniaxial or biaxial direction with the conventionally well-known extending | stretching apparatus. At this time, the application timing of the resin composition is not particularly limited, and a method (in-line method) for forming the resin composition layer at any stage of the film production process may be employed. Moreover, after extending | stretching the said base material and obtaining a stretched film, the method (offline system) of forming the layer which consists of a resin composition on the said film is also employable.

  As above-mentioned as a molded object obtained from the said resin composition, an optical member, such as a light-diffusion plate, a light-diffusion sheet, and a light-diffusion film, the anti-blocking film used for packaging materials, etc. are mentioned. In particular, since the polymer fine particles of the present invention do not contain a decomposition product having toxicity derived from AIBN, they are also suitably used as food packaging materials. When the molded body is a light diffusing sheet and a light diffusing film, the film thickness is preferably 300 μm or less, and when it is a light diffusing plate, the thickness is preferably 8 mm or less. In the case of a blocking film, the thickness is preferably 0.5 mm or less.

  What is necessary is just to manufacture a light-diffusion plate according to the manufacturing method of the molded object of the form of said (i). That is, the resin composition may be extruded into a desired thickness and shape by melt kneading with a known extruder. When manufacturing a light diffusing plate, among the above-mentioned binder resins, it is preferable to use a polycarbonate resin, a (meth) acryl-styrene resin, a polystyrene resin, or the like.

  In addition, when the resin composition is melt-extruded, the polymer fine particles may be used in advance as a master batch by being melt-kneaded with a part of the binder resin, and when being supplied to the extruder, The above binder resin and the above polymer fine particles may be mixed and used. From the viewpoint of preventing segregation of polymer fine particles in the molded product, it is preferably used as a master batch.

  What is necessary is just to manufacture a light-diffusion film according to the manufacturing method of the molded object of the form of said (ii). That is, a resin composition layer may be formed by applying a coating solution (including an organic solvent if necessary) prepared using the above resin composition on a substrate prepared in advance. When manufacturing a light-diffusion film, it is preferable to use a polyester-type resin, an acrylic resin, and a polycarbonate-type resin among the above-mentioned binder resins.

  In addition, a light-diffusion film can also be manufactured according to the manufacturing method of the form of said (i). Moreover, you may extend | stretch the molded object obtained as needed to the uniaxial or biaxial direction.

  The anti-blocking film can be produced according to the production method of any of the above (i) and (ii). When manufacturing according to the manufacturing method of the form of (i), specifically, a resin composition in which the base resin of the film and the polymer fine particles of the present invention (used as an antiblocking agent) are mixed is melted by heat. What is necessary is just to shape | mold into a film. Examples of the base resin include thermoplastic resins, for example, polyolefins such as polyethylene and polypropylene, and polyesters such as polyethylene terephthalate (PET).

  The blending amount of the polymer fine particles when the polymer fine particles of the present invention are used as an antiblocking agent is preferably 0.001 to 5% by mass with respect to the thermoplastic resin, for example. More preferably, it is 0.005-3 mass%, More preferably, it is 0.01-2 mass%. Usually, since it is difficult to blend such a small amount, a master batch in which a predetermined amount of polymer fine particles is blended is manufactured in advance, and the master batch is blended with a thermoplastic resin to produce a thermoplastic resin for a film. Then, what is necessary is just to heat-melt the said thermoplastic resin composition for films, and to shape | mold into a film. If it is necessary to stretch the film, a stretching process may be performed using a conventionally known stretching apparatus. At this time, as a stretching apparatus, a conventionally known stretching apparatus can be used, and conditions such as a melting temperature and a stretching ratio may be appropriately determined according to the use of the base resin or film to be used.

  Moreover, an anti-blocking film can also be manufactured according to the manufacturing method of the molded object of the form of said (ii). That is, a resin composition layer may be formed by applying a coating liquid containing a resin composition and a binder resin on a base material prepared in advance.

  The polymer fine particles of the present invention have good heat resistance. Therefore, when the polymer fine particles of the present invention are used as an anti-blocking agent, the polymer fine particles are not easily discolored even when exposed to high processing temperatures when the resin composition is processed into a film, so that coloring of the film is suppressed. The In addition, since the fine particles of the present invention do not contain harmful degradable organisms derived from AIBN, the anti-blocking film is a general packaging material, a food packaging material such as a food packaging film, or a pharmaceutical product such as a pharmaceutical packaging film. It is suitably used as a packaging material.

  The polymer fine particles of the present invention may be used in addition to the above-mentioned optical materials and film antiblocking agents, for example, toner additive for electrostatic charge image development, additive for decorative plate, additive for artificial marble, chromatography column. It is also suitably used as a filler, a liquid crystal display panel gap adjusting agent, a Coulter counter display particle, an immunodiagnostic carrier, a cosmetic additive, and the like.

  Hereinafter, the present invention will be described in more detail based on examples. However, the written examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are encompassed within the technical scope of the present invention. Unless otherwise specified, mass parts may be expressed as “parts” and mass% as “%”. Various measurements and evaluations were performed according to the following methods.

[Decomposition temperature]
The thermal decomposition start temperature of the polymer fine particles is 15 mg of sample using a thermal analyzer (DTG-50M, manufactured by Shimadzu Corporation), a heating rate of 10 ° C./min (maximum temperature of 500 ° C.), in the air , And measured at a flow rate of 20 ml / min. First, using a precision balance, weigh a 15 mg sample in a specified aluminum cup, place this aluminum cup in a predetermined position on the thermal analyzer, and adjust the air to flow at a specified flow rate (20 ml / min). After the apparatus was stabilized, temperature increase was started. The intersection of the extension line of the base line (horizontal line part) of the TG curve obtained at this time and the tangent line of the mass decreasing part (lower right oblique line part) was defined as the thermal decomposition start temperature of the polymer fine particles.

[Color difference]
35 g of polymer fine particles obtained in the following experimental example were packed in a colorless and transparent bag (80 mm × 60 mm) made of polyethylene, and a measurement sample having a bag thickness of about 1.5 cm was prepared. A color difference meter (trade name “SE-2000”, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure and correct the standard white plate before measuring the sample, and then the sample was measured. The color difference is measured for the polymer fine particles immediately after the production and after the heating test, the value immediately after the production is the initial b value, the value after the heating test is the b value after heating, and these differences (b value after heating−initial b) Value) as a Δb value.

  The heating test was performed as follows. About 100 g of polymer fine particles were spread in a 15 cm × 20 cm container, which was left in a hot air dryer heated to 100 ° C. for 1 hour, then taken out and allowed to cool to room temperature in air. The color difference of the polymer fine particles after the heating test was measured in the same manner.

[Content of Antioxidant (Phosphorus, Phenol) in Polymer Fine Particles-1]
Preparation of sample solution 1 g of a weighed sample (polymer fine particles) was mixed with 10 ml of chloroform and subjected to ultrasonic treatment to extract dissolved components in the fine particles. 100 ml of methanol was added to the resulting solution to insolubilize the polymer component, followed by filtration, and the resulting solution was concentrated. Next, 2 ml of chloroform was added thereto for dilution, and further acetonitrile was added to make a total volume of 10 ml. The obtained solution was filtered with a filter having a pore diameter of 0.45 μm to obtain a sample solution.

Preparation of Standard Solution 12 mg of the antioxidant used in the following Examples and Comparative Examples was weighed into a 25 ml volumetric flask, dissolved by adding 5 ml of chloroform, and diluted with acetonitrile to prepare a 25 ml solution (concentration 480 ppm). This solution was appropriately diluted with acetonitrile to obtain a standard solution (96 ppm, 19.2 ppm, 3.8 ppm). This standard solution was analyzed by high performance liquid chromatography (“NANOSPACE SI-2” manufactured by Shiseido Co., Ltd., column: “CAPCELL PAK MG” manufactured by Shiseido Co., Ltd., film thickness: 5 μm, 1.5 mm ID × 150 mm, detector: photodiode array). A calibration curve was created.

Measurement of content of antioxidants (phosphorus and phenol) The sample solution prepared by the above procedure was subjected to high performance liquid chromatography (“NANOSPACE SI-2” manufactured by Shiseido Co., Ltd.), column: “CAPCELL PAK MG manufactured by Shiseido Co., Ltd. The film thickness is 5 μm, 1.5 mm ID × 150 mm, detector: photodiode array), and the amount of antioxidant contained in the polymer fine particles of the following examples and comparative examples is determined from a calibration curve prepared in advance with a standard solution. Calculated. Measurement conditions are as follows.
Measurement conditions Column thermostat: 40 ° C
Eluent: methanol / acetonitrile = 50/50
Flow rate: 100 μl / min
Sample injection volume: 10 μl
Detection wavelength: 280 nm

[Content of Antioxidant (Sulfur) in Polymer Fine Particles -2]
Preparation of sample solution 0.2 g of a weighed sample (polymer fine particles) is put in a mixed solution of ± α-tocopherol (5% toluene solution) 1 ml and chloroform 3 ml, and subjected to ultrasonic treatment for 15 minutes to disperse the fine particles. The mixture was allowed to stand at room temperature, and the sulfur-based antioxidant in the polymer fine particles was extracted. After 15 hours, the ultrasonic treatment was performed again for 15 minutes, and the mixture was allowed to stand at room temperature for 2 days and nights to extract the sulfur-based antioxidant in the polymer fine particles. Thereafter, the extract was filtered through a disk filter having a pore size of 0.45 μm, the solvent was distilled off, and the total amount of the obtained residue was dissolved in 15 ml of toluene to obtain a sample solution.

Preparation of Standard Solution A standard solution (96 ppm, 19.2 ppm, 3.8 ppm) was prepared in the same manner as in [Antioxidant Content-1] except that toluene was used as a solvent, and a liquid chromatograph was prepared. A calibration curve was prepared by analyzing with a mass spectrometer (LS-MS, “NANOSPACE SI-2” manufactured by Shiseido Co., Ltd., detector: “LC-Q DECA XP” manufactured by ThermoQuest).

Measurement of sulfur-based antioxidant content Sample solution prepared by the above procedure was subjected to high performance liquid chromatography (“NANOSPACE SI-2” manufactured by Shiseido Co., Ltd., detector: “LC-Q DECA XP” manufactured by ThermoQuest) The amount of sulfur-based antioxidant contained in the polymer fine particles of the following examples and comparative examples was calculated from a calibration curve prepared in advance with a standard solution. The measurement conditions were as follows. Measurement was performed five times under the following conditions, and the average value of the obtained measurement values was taken as the content.
Measurement conditions Detection method (method): Ion trap type Detection conditions: Ionization method
APPI method Positive ion detection M / z: 50-2000
APPI method Negative ion detection M / z: 50-2000
Column temperature: 45 ° C
Eluent: Toluene Flow rate: 100 μl / min

[Sulfur element content in polymer fine particles]
The content of the elemental sulfur contained in the polymer fine particles was obtained by decomposing the polymer fine particles obtained in Examples and Comparative Examples described later with an acid aqueous solution, using an inductively coupled high-frequency plasma emission spectrometer (ICP, Shimadzu Corporation). "ICPE-9000" manufactured).

[Average particle diameter (median diameter), volume-based most frequent particle diameter, number-based most frequent particle diameter, coefficient of variation]
After sufficiently blending 0.4 g of polymer fine particles with 2 g of a surfactant (“Neoperex (registered trademark) G-15”, sodium dodecylbenzenesulfonate, manufactured by Kao Corporation), the dispersion is dispersed in 30 g of ion-exchanged water. To prepare a polymer fine particle dispersion.

  The measurement was performed using a disk centrifugal high-resolution particle size distribution measuring apparatus (“DC12000”, manufactured by CPS Instruments) according to the measuring method described in the instruction manual attached to the apparatus. First, a sucrose solution having a predetermined concentration (8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%) was prepared. Next, the disk-shaped measuring solvent tank was filled with a sucrose solution prepared in advance so that the sucrose concentration increased from the center to the circumference. In addition, the outermost layer (circumferential part) of the measurement solvent tank is covered with dodecane (oil layer).

After calibrating the instrument using a standard sample dispersion (0.1 ml, average particle size 0.46 μm) with a known particle size described in the attached instruction manual, the polymer fine particle dispersion was sampled. The sample was injected from the inlet and measured under the following measurement conditions to determine the volume-based and number-based most frequent particle size, average particle size, and variation coefficient of the particle size. In the measurement, the most frequent particle diameter (volume basis, number basis) was 0.3 μm as the measurement lower limit.
Measurement conditions Measurement particle diameter width: 0.3 μm to 15 μm
Refractive index of particles: 1.5
Specific gravity of particles: 1.385 g / ml
Particle sphericity: 1
Standard particle size for calibration: 0.46 μm
Density of calibration standard particles: 1.385 g / ml
Density of sucrose solution: 1.044 g / ml
Refractive index of sucrose solution: 1.36
Viscosity of sucrose solution: 1.268 cps

Coefficient of variation of particle diameter (%) = (σ / d50) × 100
Here, σ is the standard deviation of the particle size, and d50 is the mass-based average particle size.

  In Table 1, “average particle size” means a particle size of 50% in the cumulative distribution in the particle size distribution on each of the number basis and the volume basis. Further, the “fine particle amount” means fine particles contained in the polymer fine particles obtained in the following experimental examples. Here, the fine particle amount is represented by [(volume maximum frequency in the number-based particle size distribution diagram). Based on the value of (particle diameter) × 50%], the amount of particles having a particle diameter equal to or smaller than the value of the above formula is shown. The criteria for determining the amount of fine particles were evaluated as “the amount of fine particles is large” when the amount of fine particles exceeds 45% and “the amount of fine particles is small” when the amount is 45% or less.

[Tetramethylsuccinonitrile content in polymer particles]
1) Preparation of test solution 0.5 g of polymer fine particles obtained in the following examples and comparative examples were subjected to reflux extraction for 1 hour in 20 ml of methanol, the obtained extract was filtered, and the filtrate was 50 ml with methanol. To prepare a test solution.

2) Preparation of standard solution 50 mg of TMSN (tetramethylsuccinonitrile) was dissolved in acetone and fixed in 50 ml to prepare a standard stock solution. This standard stock solution was diluted with methanol to prepare standard solutions of various concentrations (0.05 μg / ml, 0.1 μg / ml, 0.5 μg / ml, 1 μg / ml).

3) Measurement by Gas Chromatograph-Mass Spectrometer With respect to the standard solution and the test solution, the amount of tetramethylsuccinonitrile contained in the polymer fine particles obtained in the following Examples was measured by a gas chromatograph-mass spectrometer under the following conditions.

Measurement conditions Model: QP-5050A (manufactured by Shimadzu Corporation)
Column: DB-5MS (J & W SCIENTIFIC)
φ0.25mm × 30m, film thickness 0.25μm
Injection method: Split (5: 1)
Injection volume: 1 μl
Temperature: Inlet: 80 ° C
Column: 60 ° C, hold for 5 minutes → 10 ° C / min temperature rise → 160 ° C
Gas pressure: Helium (carrier gas) 100 kPa
Ion source temperature: 280 ° C
Ionization voltage: 70 eV
Ionization method: EI
Set mass number: m / z 69.54

Production of polymer fine particles Experimental Example 1
Into a flask equipped with a stirrer, an inert gas introduction tube, a reflux condenser and a thermometer, polyoxyethylene distyryl phenyl ether sulfate ammonium salt (“Hitenol (registered trademark) NF-08”, Daiichi Kogyo Seiyaku Co., Ltd.) 150 parts of deionized aqueous solution in which 1 part was dissolved, 75 parts of methyl methacrylate prepared in advance, 25 parts of trimethylolpropane trimethacrylate (TMPTMA), 2 parts of lauryl peroxide (LPO) and thiosalicylic acid ( TSA) After charging a monomer solution in which 1 part was dissolved, T.S. K. The mixture was stirred at 8000 rpm for 5 minutes with a homogenizer (manufactured by Tokushu Kikai Kogyo Co., Ltd.) to obtain a uniform suspension, and 150 parts of deionized water was further added.

Next, the reaction vessel was kept at 65 ° C. by heating until the liquid temperature reached 65 ° C. while blowing nitrogen gas into the flask. The reaction starts when the liquid temperature reaches 75 ° C. due to self-heating. After stirring at this temperature for 1.5 hours, the liquid temperature is further raised to 85 ° C. and stirred for 2 hours to complete the polymerization reaction. I let you. Thereafter, the reaction solution was cooled and filtered, and the polymerization product was dried with a hot air dryer at 80 ° C. for 3 hours to obtain polymer fine particles 1.
The average particle diameter (median diameter, the same applies hereinafter) of the obtained polymer fine particles 1 was 1.02 μm.

Experimental example 2
Polymer fine particles 2 were obtained in the same manner as in Experimental Example 1, except that 2 parts of azobisisobutyronitrile (AIBN) was used as the polymerization initiator.
The average particle diameter of the obtained polymer fine particles 2 was 1.04 μm.

Experimental example 3
Using 2 parts of non-nitrile-azo initiator (“V-601”, dimethyl-2,2′-azobis (2-methylpropionate), manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, a single amount A body solution obtained by adding 0.1 part of a hindered phenol antioxidant (“Irganox (registered trademark) 1010”, manufactured by Ciba Specialty Chemicals) to the monomer solution of Experimental Example 1 Except that it was used, polymer fine particles 3 were obtained in the same manner as in Experimental Example 1.
The average particle diameter of the obtained polymer fine particles 3 was 1.06 μm.

Experimental Example 4
The use of 2 parts of a non-nitrile-azo initiator (“V-601”) as a polymerization initiator, the monomer solution of Experimental Example 1 as a monomer solution, and PETG (pentaerythritol as a thiol compound) Polymer fine particles 4 were obtained in the same manner as in Experimental Example 1, except that 0.5 part of tetrakisthioglycolate (manufactured by Sakai Chemical Co., Ltd.) was used.
The average particle diameter of the obtained polymer fine particles 4 was 1.06 μm.

  Table 1 shows the blending compositions of Experimental Examples 1 to 4 and the evaluation results of the obtained polymer fine particles 1 to 4.

  In Table 1, “MMA” means methyl methacrylate and “TMPTMA” means trimethylolpropane trimethacrylate.

  From Table 1, the polymer fine particle of Experimental Example 1 using a peroxide-based polymerization initiator had a dn / dw value of 0.38 and a large amount of fine particles, whereas the non-nitrile-azo-based start The dn / dw values of Experimental Examples 3 and 4 using the agent were 0.51 (Experimental Example 3) and 0.52 (Experimental Example 4), and the amount of fine particles was small. Experimental Examples 3 and 4 had the same amount of fine particles as the fine particles (Conventional Example) of Experimental Example 2 using AIBN.

  From these results, even when non-nitrile-azo initiators are used, by using a thiol compound and an antioxidant together, the content of fine particles equivalent to conventional polymer fine particles and initiation of thermal decomposition are started. It can be seen that fine polymer particles having a temperature and free of harmful decomposition products can be obtained.

  Further, when comparing the particle size distributions of the experimental examples 1 and 3 (number basis, volume basis, FIGS. 2 to 5), the volume basis particle size distribution shows the same most frequent particle size, but the number basis particle size In the distribution, in Experimental Example 1 (dn / dw = 0.38) in which the ratio dn / dw between the number-based most frequent particle diameter and the volume-based most frequent particle diameter is less than 0.45, Experimental Example 3 (dn / It can be seen that the amount of particles having a small particle diameter is small compared to dw = 0.51) (FIGS. 3 and 5). In Experimental Example 3, the amount of fine particles was 38.8%, which was small compared to Experimental Example 1. That is, the amount of fine particles contained in the fine particles after polymerization can be determined from the ratio dn / dw between the most frequent particle diameter based on the number and the most frequent particle diameter based on the volume, and when the dn / dw is 0.45 or more. It can be seen that the polymer fine particles have a reduced content of fine particles of a predetermined size.

  The polymer fine particles of the present invention are excellent in heat resistance and not only have a narrow particle size distribution but also have a reduced content of fine particles. Therefore, after mixing with other resins, etc., it is difficult to cause deterioration of the polymer fine particles, and further to defects (coloring, etc.) on the molded product even when exposed to high temperature, and the particle size distribution is higher. It is also suitable for applications that require control with level accuracy. Furthermore, since the polymer fine particles of the present invention contain little or no toxic decomposition products (by-products) derived from specific polymerization initiators, they can be used in a wide range of fields including medical and food fields. Can be used. Specifically, the polymer fine particles of the present invention include an antiblocking agent for resin films, an optical resin material that imparts light diffusibility and antireflection antiglare properties to various display devices, a spacer for liquid crystal, and an electrostatic charge image developing toner. Additives, powder paints and water dispersion type paints, decorative plate additives, artificial marble additives, cosmetic fillers, chromatography column fillers, light diffusing agents, abrasives, etc. It can be applied to various fields such as optical materials and chemical products. In particular, it is suitably used as various additives such as anti-blocking agents for food packaging materials.

It is a schematic diagram which shows the form of the polymer fine particle of this invention. It is a figure which shows the particle size distribution (volume basis) of the polymer fine particle 1. It is a figure which shows the particle size distribution (number basis) of the polymer fine particle 1. FIG. It is a figure which shows the particle size distribution (volume basis) of the polymer fine particle 3. It is a figure which shows the particle size distribution (number basis) of the polymer fine particle 3.

Claims (7)

A Ru polymer microparticles name by polymerizing a monomer composition containing an azo radical polymerization initiator, - (meth) monomer component and a non-nitrile containing acrylic monomer
The monomer composition further contains a hindered phenol antioxidant and / or a thiol compound, or the polymer fine particles are mixed with a hindered phenol antioxidant or hindered phenol antioxidant. Soaked in an antioxidant solution in which the agent is dissolved or dispersed,
The thermal decomposition starting temperature is 310 ° C. or higher,
The volume-based most frequent particle diameter (dw) is 0.1 μm to 20 μm,
The ratio dn / dw of the number-based most frequent particle diameter (dn) to the volume-based most frequent particle diameter (dw) is 0.45 or more ,
Upper Symbol thiol compound comprises a molecular weight of 200 or more multifunctional thiol compounds, and,
A polymer fine particle having excellent heat resistance, wherein the content of tetramethylsuccinonitrile is 100 ppm or less in the polymer fine particle.   The polymer fine particles according to claim 1, further comprising thiosalicylic acid as a thiol-based compound.   The polymer fine particles according to claim 1 or 2, wherein the content of fine particles having a particle diameter of 50% or less of the most frequent particle diameter in the volume-based particle size distribution in the polymer fine particles is 45% or less.   The polymer fine particle according to any one of claims 1 to 3, wherein the monomer component further contains a crosslinkable (meth) acrylic monomer. 5. The polymer fine particle according to claim 1, wherein the polymer fine particle includes one or more selected from the group consisting of a hindered phenol-based antioxidant , a thiol-based compound , and a component in which a thiol-based compound is bonded to a polymer chain terminal. Polymer fine particles. A method for producing polymer fine particles according to any one of claims 1 to 5,
100 parts by mass of a radically polymerizable monomer containing a (meth) acrylic monomer, 0.1 part by mass to 10 parts by mass of a non-nitrile-azo radical polymerization initiator, 0.05 part by mass of a hindered phenol antioxidant The monomer composition containing 5 parts by mass to 5 parts by mass and / or 0.05 part by mass to 10 parts by mass of a thiol compound is subjected to radical polymerization, and the thiol compound includes a polyfunctional thiol compound having a molecular weight of 200 or more. A method for producing polymer fine particles.   The method for producing polymer fine particles according to claim 6, wherein the monomer composition further contains thiosalicylic acid as a thiol compound.