JP2001294631A - Acrylic aggregate, light diffusing agent, light-diffusing resin composition and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light scattering resin composition having excellent optical characteristics and impact resistance. SOLUTION: The light diffusing agent of an acrylic aggregate is obtained from an acrylic fine particle having an inner layer composed of at least one or more layers comprising an acrylic polymer having <=0 deg.C glass transition temperature (Tg) and an outermost layer composed of an acrylic polymer having >=50 deg.C Tg in an amount of >=1 mass % and <=5 mass % based on the whole acrylic fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic aggregate formed by aggregating acrylic fine particles, and more particularly, to diffusing light from an illumination cover, an illumination sign, a glazing, various displays, and the like. The present invention relates to a light diffusing agent comprising an acrylic aggregate and a light diffusing resin composition containing such a light diffusing agent suitable for a molded article.

[0002]

2. Description of the Related Art As a light-diffusing resin composition which has been widely used in the past for lighting covers and the like, in order to obtain light-diffusing properties, an inorganic material having a different refractive index from that of the transparent resin is used in the transparent resin. Examples in which organic fine particles are dispersed can be given.

[0003] Examples of transparent resins used in such applications include methacrylic resins, styrene resins, and vinyl chloride resins. Further, as the inorganic fine particles,
Average particle size of barium sulfate, calcium carbonate, quartz, etc. 10
Inorganic transparent fine particles of μm or less (JP-A-54-1552)
41, JP-B-46-43189). Further, as an alternative to these inorganic fine particles, organic fine particles obtained by copolymerizing styrene or substituted styrene with a polyfunctional monomer (JP-B-39-10515, JP-B-46-11834, JP-B-46-11834, 55-7
471 gazette) and the like.

[0004]

However, in general, when conventional fine particles are mixed with a transparent resin as a light diffusing agent, the impact strength of the light diffusing resin composition may be reduced, so that it is limited to limited applications. In some cases it could not be used.

[0005] JP-A-63-137911, JP-A-2-31885 and JP-A-7-238200
Japanese Patent Application Laid-Open Publication No. H11-216, which is composed of core / shell polymer particles for the purpose of suppressing a decrease in the physical strength of the matrix polymer when the light scattering particles are dispersed in the matrix polymer,
It is disclosed that the core comprises a rubbery alkyl acrylate having an alkyl group of 2 to 8 carbon atoms and the outer shell is miscible with the matrix polymer and accounts for about 5 to about 40% of the mass of the particles. I have.

In the above invention, a light diffusing agent is disclosed in which methacrylic resin is used as a matrix polymer (transparent resin) and an outermost layer of an acrylic polymer is formed as an outer shell. In this case, the acrylic polymer generally has excellent optical characteristics and good affinity with the methacrylic resin, so that a light-scattering resin composition having high characteristics is expected to be obtained.

However, in the above example, the glass transition temperature (hereinafter, also referred to as Tg) of the acrylic polymer is used.
Is not described in detail, and the ratio of the outermost layer to the acrylic fine particles is as high as 5% by mass or more. Therefore, when the Tg of the outermost layer is 50 ° C or more, the physical properties of the obtained light-scattering resin composition It is feared that the reduction of the mechanical strength is insufficient and the impact resistance is reduced.

Various emulsion polymerization methods have been proposed as methods suitable for producing acrylic fine particles. For example, JP-A-8-198903 discloses that a monomer or a monomer mixture is first divided into a monomer for initial addition and a monomer for dropping, and then a persulfate initiator is added. Buffer-containing aqueous medium, after the batch addition of the initial addition monomer,
Hold for a period of time to form seed particles and then
A method for producing a polymer latex (hereinafter also referred to as a seed polymerization method) in which the above-mentioned monomer for dropping is immediately dropped over a certain period of time after the persulfate initiator is again added to this polymerization system and held for a certain period of time is disclosed. ing.

In the emulsion polymerization method as described above, after the polymerization is completed, an acid or a salt is added to agglomerate the polymer latex (acrylic fine particles), and the aqueous medium is separated to form an acrylic aggregate. to recover. As a separation method,
Generally, a spray drying method or a method in which an acrylic aggregate is stirred and mixed with an appropriate aqueous solution of an aggregating agent, and a slurry containing the acrylic aggregate is dehydrated and dried.

However, when the acrylic fine particles having an inner layer and an outermost layer made of an acrylic polymer are aggregated, the proportion of the outermost layer in the acrylic fine particles greatly affects the aggregation behavior of the acrylic fine particles. The present inventors have found that this is an important factor in determining the mass average particle diameter of the obtained acrylic aggregate.

That is, when the ratio of the outermost layer to the whole acrylic fine particles is more than 5% by mass, the obtained acrylic aggregates often become fine powder having a mass average particle diameter of less than 100 μm. When an acrylic aggregate having a mass average particle diameter of less than 100 μm is used as a light scattering agent, the handleability is poor, dusting is severe, the working environment is deteriorated, and a dust explosion may occur.

When the ratio of the outermost layer to the whole acrylic fine particles is less than 1% by mass, the whole acrylic aggregates are blocked, the productivity is reduced, and powder may not be obtained. .

In view of the above situation, the present invention has excellent optical characteristics such as total light transmittance and diffusivity,
It is possible to produce a light-scattering resin composition suitable for molded articles having excellent impact resistance such as an o-d impact strength and a 50% breaking height, and it is possible to produce an acrylic resin composition having good handleability and productivity. An object of the present invention is to provide a light scattering agent composed of an aggregate.

[0014]

According to the present invention, there is provided an acrylic aggregate obtained by aggregating acrylic fine particles, wherein the acrylic fine particles have a glass transition temperature (Tg). At least one inner layer made of an acrylic polymer having a Tg of 1% by mass or more and 5% by mass or less, and
And an outermost layer made of an acrylic polymer having a temperature of 50 ° C. or higher.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic fine particles of the present invention comprise an outermost layer made of an acrylic polymer and an inner layer made of an acrylic polymer. The acrylic polymer generally has excellent optical characteristics. The resulting light-scattering resin composition has sufficient optical properties. The inner layer has a Tg of 0.
Since the polymer is a soft polymer having a temperature of not more than ° C, the obtained light-scattering resin composition has sufficient impact resistance. Further, the outermost layer is T
g is a hard polymer having a temperature of 50 ° C. or higher, and the proportion thereof is 1% by mass or more and 5% by mass or less based on the whole acrylic fine particles. It is suppressed, and sufficient impact resistance can be realized. in addition,
Since the ratio of the outermost layer is 1% by mass or more and 5% by mass or less,
The acrylic aggregate of the present invention has a preferable mass average particle diameter, and as a result, good handleability and productivity can be realized.

The outermost layer in the present invention is not particularly limited as long as it is an acrylic hard polymer having a Tg of 50 ° C. or higher, but preferably has a sufficient affinity with a transparent resin as a matrix resin. Further, from the viewpoint of polymerizability and the like, a homopolymer obtained from an alkyl methacrylate of an alkyl group having 4 or less carbon atoms; 70% by mass or more and 100% by mass or less of the alkyl methacrylate of an alkyl group having 4 or less carbon atoms, A copolymer obtained from 30% by mass or less of the copolymerizable unsaturated monomer is preferred.

Examples of the alkyl methacrylate having an alkyl group having 4 or less carbon atoms include methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate. These can be used alone or in combination of two or more. Particularly, methyl methacrylate is preferred.

The unsaturated monomers copolymerizable therewith include 1,3-butadiene, 2,3-butadiene,
Examples thereof include vinyl toluene, cyclohexyl methacrylate, benzyl methacrylate, acrylonitrile, methacrylonitrile and the like.
More than one species can be used.

The ratio of the outermost layer to the whole acrylic fine particles is set to 1% by mass or more, and 1.5% by mass in order to suppress blocking of the acrylic aggregates and to realize good productivity. The above is preferred. Further, in order to achieve good impact resistance of the light-scattering resin composition and to produce an acrylic aggregate having a sufficient mass average particle diameter and to achieve good workability, the content is set to 5% by mass or less. , 4.5 mass% or less.

The mass-average particle diameter is determined by laser diffraction /
It can be measured by a scattering method or the like. In order to realize the above-described good workability, the mass average particle diameter of the acrylic aggregate is preferably 100 μm or more, and 200 μm or more.
m or more, more preferably 300 μm or more. On the other hand, when the mass average particle diameter of the acrylic aggregate is too large, the workability is deteriorated. Therefore, the mass average particle diameter is preferably 1000 μm or less, more preferably 700 μm or less, and still more preferably 500 μm or less.

Further, the mass average particle diameter of the acrylic fine particles is preferably 1 μm or more and 5 μm or less. Because, if the mass average particle diameter of the acrylic fine particles is 1 μm or more,
Good appearance of the finally obtained molded body can be realized and 5μ
This is because good optical characteristics can be realized when the value is m or less.

The inner layer in the present invention is not particularly limited as long as it is an acrylic soft polymer having a Tg of 0 ° C. or lower, but from the viewpoint of polymerizability, a homopolymer obtained from an alkyl acrylate having an alkyl group having 8 or less carbon atoms. An alkyl acrylate having an alkyl group having 8 or less carbon atoms;
A copolymer obtained from 0% by mass or more and 100% by mass or less and 30% by mass or less of a monofunctional monomer having at least one vinyl group copolymerizable with the alkyl acrylate is preferable.

Further, from the viewpoint of the balance of properties, 0.1% by mass or more and 1% by mass with respect to 100% by mass of the monomer component in the inner layer.
0% by mass or less of a graft-linking agent and 0.1% by mass or more of 1
0% by mass or less of a polyfunctional crosslinking agent having at least two vinyl groups may be contained.

Examples of the alkyl acrylate having an alkyl group having 8 or less carbon atoms include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like, and these may be used alone or in combination of two or more. Among these, butyl acrylate, 2-
It is preferred to use ethylhexyl acrylate.

Examples of the copolymerizable monofunctional monomer having at least one vinyl group include aromatic unsaturated monomers such as styrene, vinyl toluene and α-methylstyrene; and methyl methacrylate, phenyl methacrylate and naphthyl methacrylate. A vinyl monomer and the like can be exemplified.

The graft-crosslinking agent is one in which the reactivity of at least one of the functional groups is different from that of the other, and examples thereof include allyl esters of acrylic acid, methacrylic acid, maleic acid and fumaric acid. It is preferable to use allyl acrylate or allyl methacrylate.

The polyfunctional cross-linking agent is one in which the reactivity of a plurality of functional groups is similar, and examples thereof include 1,3-butylene methacrylate and 1,4-butanediol diacrylate.

From the viewpoint of the balance of properties, two or more inner layers such as an intermediate layer and an innermost layer may be formed on acrylic fine particles.

Examples of the method for producing the acrylic fine particles in the present invention include an emulsion polymerization method, an aqueous medium polymerization method without an emulsifier, a method using an emulsion polymerization method and a polymerization method without an emulsifier in combination. It is not limited to these methods.

The mass average particle diameter is 1 μm or more and 5 μm
In the following, a seed polymerization method may be employed to produce acrylic fine particles having excellent characteristics.

As a specific example of the seed polymerization method, (a) first, the above-mentioned monomer or monomer mixture is divided into a monomer for initial addition and a monomer for dropping, and (a) , A pH buffer such as boric acid or sodium carbonate is added to the aqueous medium,
(C) While this aqueous medium is heated to 70 to 85 ° C. and stirred under an inert atmosphere, a persulfate initiator such as potassium persulfate is added, and immediately the above-mentioned monomer for initial addition is immediately added at once. And hold for a certain time to produce seed (seed) particles,
(D) Subsequently, after the persulfate initiator is again added to the polymerization system, the above-mentioned monomer for dropping is immediately dropped over a certain period of time, and the method is held for a certain period of time. be able to.

Further, an acrylic polymer is added as seed particles to an aqueous medium containing an emulsifier such as sodium mono-n-pentylphenylhexaoxyethylene phosphate and sodium di-n-pentylphenylhexaoxyethylene phosphate. In some cases, seed polymerization is performed by dropping a polymerization initiator such as a peroxide such as t-butyl hydroperoxide and a monomer and a monomer.

In order to promote the polymerization stably, the seed particles may contain a chain transfer agent such as mercaptan.

After the production of the acrylic fine particles is completed, the acrylic fine particles are agglomerated by adding a coagulant such as an acid such as sulfuric acid; a salt such as calcium carbonate or calcium acetate, and a mass average of 100 μm or more and 1000 μm or less. An acrylic aggregate having a particle diameter can be obtained. Since the amount and type of the coagulant vary depending on the amount and type of the emulsifier used when producing the acrylic fine particles, a preferable amount and type are appropriately selected.

In the present invention, since the ratio of the outermost layer to the acrylic fine particles is 1% by mass or more and 5% by mass or less, the mass average particle size of the acrylic aggregate should be 100 μm or more and 1000 μm or less. Can be.

The obtained acrylic aggregate can be recovered as a powder by filtration, centrifugation, extrusion drying, or the like.

The acrylic aggregate obtained as described above can be particularly preferably used as a light scattering agent, and the obtained light diffusing resin composition has excellent optical properties and impact resistance. Is also excellent.

The light-scattering agent of the present invention is preferably at least 1 part by mass, more preferably at least 3 parts by mass, even more preferably at least 5 parts by mass with respect to 100 parts by mass of the transparent resin in order to realize a sufficient diffusivity. The above is added. Further, in order to realize a sufficient total light transmittance, it is added preferably at most 30 parts by mass, more preferably at most 25 parts by mass, further preferably at most 20 parts by mass.

The diffusivity means the average of the ratio of the amount of diffused light at the positions of 20 ° and 70 ° to the amount of diffused light at the position of 5 ° with respect to the incident light. preferable. Further, the total light transmittance is preferably 65% or more.

Examples of the transparent resin used in the present invention include methacrylic resin, styrene resin, vinyl chloride resin and the like, and methacrylic resin is preferable from the viewpoint of affinity with the outermost layer of the acrylic fine particles.

From the viewpoint of the balance of optical characteristics,
A glass transition temperature (Tg) contained in the acrylic fine particles having a refractive index of an inner layer made of an acrylic polymer having a temperature of 0 ° C. or less;
The absolute value of the difference from the refractive index of the transparent resin is 0.01 or more.
It is preferably 1 or less.

The molded article made of the light diffusing resin composition of the present invention is obtained by adding acrylic fine particles to a transparent resin monomer, a monomer mixture, or a mixture of a polymer and a monomer (syrup). A casting polymerization method of mixing and dispersing and polymerizing in a mold;
Acrylic fine particles are mixed and dispersed in a transparent resin, and the resulting mixture is pelletized using an extruder or the like, and can be produced by extrusion molding or injection molding.

Further, as long as the object of the present invention is achieved, a face wash, a stabilizer, and other additives may be added in order to increase the commercial value.

As the impact resistance of the finally obtained molded product, the Izod impact strength of the molded product is 2000 J / m.
^It is preferably at least ^2, more preferably at least 2500 J / m ² .

As the impact resistance of the finally obtained molded article, the 50% breaking height of the molded article is preferably 0.19 m or more, more preferably 0.20 m or more.

In the present invention, the ratio of the outermost layer to the acrylic fine particles is 1% by mass or more and 5% by mass or less, so that the above-mentioned preferable mechanical properties can be realized.

Since the light-diffusing resin composition of the present invention is excellent in optical properties and impact resistance, it is a molded article aimed at diffusing light for lighting covers, lighting signs, glazing, various displays and the like. And can be suitably used.

[0048]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

MMA is methyl methacrylate, 2
EHA is 2-ethylhexyl acrylate, BA is butyl acrylate, KPS is potassium persulfate, AMA is allyl methacrylate, 1,3BD is 1,3-butylene methacrylate, and St is styrene.

Unless otherwise specified, all reagents are commercially available good products, and parts are parts by mass.

[Preparation of Test Piece] (A) Injection molding machine: V-17-6, manufactured by Japan Steel Works, Ltd.
5-type screw-type automatic injection molding machine, (a) Injection molding conditions: cylinder temperature 250 ° C, injection pressure 70 MPa, (c) Specimen size: Specimen 1: 100 mm x 100 m
mx 2 mm (thickness), Test piece 2: 70 mm x 12.5 mm x 2 mm (thickness).

[Evaluation Method] (A) Glass transition temperature Tg (° C.): An acrylic polymer having the same composition as the acrylic polymer constituting the inner layer and the outer layer is produced by cast polymerization, and each side is 0.5 mm or less. And cut into a cube according to JIS K 7121.
The glass transition temperature Tg was measured by DSC30 manufactured by Ller.

(A) Mass average particle diameter (μm): A laser diffraction / scattering type particle size distribution measuring apparatus is used to measure the mass average particle diameter of acrylic fine particles and an acrylic aggregate obtained by aggregating the acrylic fine particles. (Made by Horiba,
LA-910).

(C) Refractive index: An acrylic polymer having the same composition as the acrylic polymer constituting the inner layer was produced by cast polymerization, and a plate having a thickness of 3 mm was produced. By injection molding transparent resin raw material pellets,
mm plates were produced. JIS for each board
K7105 according to Kalnew Optical Co., Ltd.
The refractive index was measured by PR-2. The value at 23 ° C. and D line (λ = 589 mm) was defined as the refractive index.

(D) Total light transmittance (%): Measured using test piece 1 in accordance with ASTM D-1003-61. 65% or more was regarded as pass (○), and less than 65% was rejected (x).

(E) Diffusivity (%): As shown in FIG.
The measuring equipment and the test piece were arranged. In the figure, (1) is a collimator manufactured by Nippon Kogaku as a light source, (2) is a test piece 1,
(3) is a luminance meter (auto spot) manufactured by Minolta. Among them, the light source (1) irradiates the test piece 1 surface of (2) at a right angle, and adjusts the brightness so that the illuminance on the test piece 1 surface of (2) becomes 10 ft-cd. The luminance meter (3) was placed at a position 1 m above the extension of the test piece 1 of the light sources (1) and (2), and the luminance on the surface of the test piece (2) was measured. Further, the luminance meter (3) is connected to the test piece 1 of (2).
Was rotated at 5 °, 20 °, and 70 ° around an axis centered at, and the luminance on one surface of the test piece of (2) was measured.

Using the obtained luminance (diffusion light amount), the diffusion rate was calculated according to the following equation.

Diffusivity (%) = ｛(luminance at 20 ° +
Luminance at 70 °) / (Luminance at 5 ° × 2)｝ ×
100.

The case where the calculated diffusion rate was 55% or more was judged as pass (○), and the case where it was less than 55% was judged as failed (×).

(F) Notched Izod impact strength (J /
m ² ): Measured using test piece 2 in accordance with ASTM D-256.

(G) 50% breaking height (m): 50% RH at 23 ° C. using a Dupont impact strength tester shown in FIG.
The test piece 1 held for 48 hours in the environment of
An m-diameter firing pin was brought into contact. Thereafter, a 200 g weight was dropped freely from the vertical direction to collide with the firing pin, and the height at which half of the test pieces 1 broke, that is, the 50% breaking height was evaluated as an index of the surface impact strength. In addition, 20 test pieces were created for each evaluation sample, measured, and the obtained results were averaged.

Example 1 Light-scattering resin composition 1 (a) Production of first inner layer: 300 parts of deionized water, 0.9 part of boric acid and 0.09 part of sodium carbonate were charged into a reaction vessel and reacted. The temperature in the vessel was raised to 80 ° C.,
Immediately after charging 2 parts, 5 parts of 2EHA was charged and polymerization was started.

The deionized water, the monomer and the dropping monomer in the reaction vessel are replaced with nitrogen to replace the oxygen contained therein, so that the polymerization is not substantially inhibited.
(Hereinafter, simply referred to as nitrogen substitution.) 40 minutes after the start of the polymerization, 95 parts of 2EHA was dropped into the reaction vessel over 5 hours, and 1 hour and 5 hours after the start of the dropping, 0.05 parts of KPS was additionally added. did. One hour after the completion of the dropwise addition, 0.05 parts of KPS was further added, and the inside of the reaction vessel was heated to 85 ° C and held for 1.5 hours. The mass average particle diameter of the polymer after recovery was 1.6 μm. The Tg of the polymer constituting the first inner layer was -55 ° C.

(A) Preparation of the second inner layer: 25 parts of the polymer obtained in (a) and 300 parts of deionized water were charged into a reaction vessel on a solid basis, and the inside of the reaction vessel was replaced with nitrogen.
C., and a mixture of 75 parts of 2EHA and 2.0 parts of AMA was dropped into the reaction vessel over 7 hours. Also, KPS
2 hours, 4.5 hours, and 7 hours after the start of dropping, 0.05 part of each was charged into the reaction vessel. The Tg of the polymer constituting the second inner layer was −53 ° C.

(C) Production of the outermost layer: 97 parts of the polymer obtained in (b) were charged into a reaction vessel on a solid basis, and the inside of the reaction vessel was purged with nitrogen and then heated to 80 ° C. afterwards,
A mixture obtained by mixing 3 parts of MMA and 0.003 parts by mass of a polymerization initiator t-butyl hydroperoxide was charged into the reactor and kept for 1 hour. The mass average particle diameter of the acrylic fine particles after collection was 2.3 μm. The Tg of the polymer constituting the outermost layer was 105 ° C.

(D) Production of acrylic aggregate: 50 parts by mass of an aqueous solution of calcium acetate adjusted so that the concentration of calcium acetate is 1% by mass is based on 100 parts by mass of the acrylic fine particles obtained in (C). , The temperature in the stirring tank is 25 ° C
While stirring to obtain an acrylic aggregate. The mass average particle diameter of the obtained acrylic aggregate is 420 μm.
And the handleability was good.

(E) Evaluation: The obtained acrylic aggregate was mixed with a methacrylic resin (Acrypet (registered trademark) VH: a product of Mitsubishi Rayon Co., Ltd.) in the composition shown in Table 1 and extruded. After pelletizing using, a test piece was prepared by injection molding. Table 1 shows the evaluation results of the test pieces thus obtained.

The absolute value of the refractive index difference between the polymer constituting the first inner layer and the second inner layer of the acrylic fine particles and the Acrypet VH was 0.012 and 0.011, respectively.

As described above, the light diffusing agent of the present invention has good handleability and productivity, excellent optical characteristics such as total light transmittance and diffusivity, and Izod impact strength and 50% breaking height. It was found that a light-scattering resin composition having excellent impact resistance could be produced.

Example 2 Light Scattering Resin Composition 2 (A) Production of Inner Layer: 300 parts of deionized water, boric acid 0.9
Parts, 0.09 part of sodium carbonate was charged into the reactor, and the atmosphere in the reactor was replaced with nitrogen. After the temperature in the reaction vessel was raised to 80 ° C., 0.001 part of KPS was added under stirring and under a nitrogen flow, and immediately. , A mixture of 5 parts of BA and 0.1 part of n-octyl mercaptan was charged to initiate polymerization.

Forty minutes after the start of the polymerization, 45 parts of BA and AMA
A mixture of 2.0 parts of n-octyl mercaptan and 0.5 part of n-octyl mercaptan was added dropwise over 2.5 hours, and the mixture was kept for 30 minutes.
A mixture of 0 parts, 2.0 parts of AMA, and 1.0 part of 1,3BD was added dropwise over 2.5 hours. After 1.5 hours, 3 hours, and 5.5 hours from the start of the first dropping, 0.05 parts of KPS was added.
C. for 2.5 hours. Immediately after the completion of the dropwise addition, 0.2 part by mass of a 1: 1 mixture of sodium mono-n-pentylphenylhexaoxyethylene phosphate and sodium di-n-pentylphenylhexaoxyethylene phosphate was added as an emulsifier. Tg of the polymer constituting the inner layer
Was -45 ° C.

(A) Production of the outermost layer: Polymerization was carried out in the same manner as in the case of the light-scattering resin composition 1, except that the polymer obtained in the above (A) was used. The mass average particle diameter of the obtained acrylic fine particles was 1.5 μm. The Tg of the polymer constituting the outermost layer was 105 ° C.

(C) Production of acrylic aggregate: except that the acrylic fine particles obtained in (a) above were used,
An acrylic aggregate was produced in the same manner as in the case of the light-scattering resin composition 1. The mass average particle diameter of the obtained acrylic aggregate was 440 μm, and the handleability was good.

(D) Evaluation: Test pieces were prepared and evaluated in the same manner as in the case of the light-scattering resin composition 1, and the results were evaluated.
It was shown to. The absolute value of the difference in refractive index between the polymer constituting the inner layer of the acrylic fine particles and the Acrypet VH is 0.1.
024.

As described above, the light diffusing agent of the present invention has good handleability and productivity, is excellent in optical characteristics such as total light transmittance and diffusivity, and has Izod impact strength and 50% breaking height. It was found that a light-scattering resin composition having excellent impact resistance could be produced.

[Example 3] Light scattering resin composition 3 (A) Production of second inner layer: (A) of light scattering resin composition 2
40 parts on a solid basis of the polymer obtained in the above, 1.1 parts of deionized water, and sodium mono-n-pentylphenylhexaoxyethylene phosphate and di-n-pentylphenylhexaoxyethylene sodium phosphate The reactor was charged with 0.2 part of a 1: 1 mixture and purged with nitrogen, and the temperature inside the reaction vessel was raised to 80 ° C. Thereafter, a mixture of 60 parts of BA, 2.0 parts of AMA, and 0.2 parts by mass of a polymerization initiator t-butyl hydroperoxide was dropped into the reaction vessel over 3.5 hours to perform polymerization. The Tg of the polymer constituting the second inner layer was -43 ° C.

(A) Production of the outermost layer: Polymerization was carried out in the same manner as in the case of the light-scattering resin composition 1 except that the polymer obtained in the above (A) was used. The mass average particle diameter of the obtained acrylic fine particles was 2.0 μm. The Tg of the polymer constituting the outermost layer was 105 ° C.

(C) Production of acrylic aggregate: except that the acrylic fine particles obtained in (a) above were used,
An acrylic aggregate was produced in the same manner as in the case of the light-scattering resin composition 1. The mass average particle diameter of the obtained acrylic aggregate was 425 μm, and the handleability was good.

(D) Evaluation: Test pieces were prepared and evaluated in the same manner as in the case of the light-scattering resin composition 1, and the results were evaluated.
It was shown to. Note that the absolute value of the refractive index difference between the polymer constituting the second inner layer of the acrylic fine particles and the Acrypet VH is:
0.024.

As described above, the light diffusing agent of the present invention has good handleability and productivity, is excellent in optical characteristics such as total light transmittance and diffusivity, and has Izod impact strength and 50% breaking height. It was found that a light-scattering resin composition having excellent impact resistance could be produced.

Example 4 Light Scattering Resin Composition 4 (A) Production of Third Inner Layer: Light Scattering Resin Composition 3 (A)
40 parts on a solid basis of the polymer obtained in the above, 1.1 parts of deionized water, and sodium mono-n-pentylphenylhexaoxyethylene phosphate and di-n-pentylphenylhexaoxyethylene sodium phosphate 0.2 parts of a 1: 1 mixture was charged into a reactor and polymerized in the same manner as in the case of the light-scattering resin composition 3. The Tg of the polymer constituting the third inner layer was -43 ° C.

(A) Production of the outermost layer: Polymerization was carried out in the same manner as in the case of the light-scattering resin composition 1, except that the polymer obtained in the above (A) was used. The mass average particle diameter of the obtained acrylic fine particles was 2.6 μm. The Tg of the polymer constituting the outermost layer was 105 ° C.

(C) Production of acrylic aggregate: except that the acrylic fine particles obtained in (a) above were used,
An acrylic aggregate was produced in the same manner as in the case of the light-scattering resin composition 1. The obtained acrylic aggregate had a mass average particle size of 410 μm, and the handleability was good.

(D) Evaluation: Test pieces were prepared and evaluated in the same manner as in the case of the light-scattering resin composition 1, and the results were evaluated.
It was shown to. Note that the absolute value of the refractive index difference between the polymer constituting the third inner layer of the acrylic fine particles and the Acrypet VH is:
0.024.

As described above, the light diffusing agent of the present invention has good handleability and productivity, excellent optical characteristics such as total light transmittance and diffusivity, and Izod impact strength and 50% breaking height. It was found that a light-scattering resin composition having excellent impact resistance could be produced.

Comparative Example 1 Light scattering resin composition 5 The inner layer / outermost layer had a mass ratio of 80/20 and the inner layer was BA.
/ St (mass ratio: 95/5), and the outermost layer is M
Acrylic fine particles of MA having a mass average particle diameter of 2 μm were aggregated in the same manner as in the case of the light-scattering resin composition 1. The obtained acrylic aggregate has a mass average particle diameter of 6
The particle size was 0 μm, the powder was severe, and the handleability was poor.

Further, test pieces were prepared and evaluated in the same manner as in the case of the light-scattering resin composition 1, and the results were shown in Table 1. The inner layer had a Tg of -40 ° C, and the outermost layer had a Tg of 1
And the absolute value of the refractive index difference between the polymer constituting the inner layer of the acrylic fine particles and the Acrypet VH is 0.05 ° C.
It was 18.

[Comparative Example 2] Light scattering resin composition 6 An acrylic aggregate was prepared in the same manner as in the case of light scattering resin composition 5, except that the mass ratio of the inner layer / outermost layer was changed to 70/30. Manufactured and evaluated. The mass average particle diameter of the obtained acrylic aggregate was 40 μm, the powder was violent, and the handleability was poor.

COMPARATIVE EXAMPLE 3 Light scattering resin composition 7 A bead made of 100 parts by mass of polystyrene having a Tg of 100.degree.
6 parts by mass with respect to 0 parts by mass, light-scattering resin composition 1
The evaluation was performed in the same manner as in the above.

The above-mentioned beads and Acrypet VH
The absolute value of the refractive index difference was 0.100.

[Comparative Example 4] Light scattering resin composition 8 Light scattering resin composition 1 using only ACRYPET VH
The evaluation was performed in the same manner as in the above.

[0092]

[Table 1]

[0093]

As described above, the acrylic fine particles are contained in at least one inner layer made of an acrylic polymer having a Tg of 0 ° C. or less, and 1% by mass to 5% by mass with respect to the whole acrylic fine particles. The light diffusing agent of the acrylic aggregate obtained from the acrylic fine particles by forming from the outermost layer made of the acrylic polymer having a Tg of 50 ° C. or higher has good handleability and productivity. Thus, a light-scattering resin composition having excellent optical properties and impact resistance can be produced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a diffusivity measuring device.

FIG. 2 is a schematic diagram illustrating a Dupont-type impact strength tester.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) G02B 5/02 G02B 5/02 B F term (reference) 2H042 BA02 BA13 BA15 BA18 BA20 4F070 AA32 AB08 AB23 AC76 AC78 AC83 DA39 DC07 DC11 4F071 AA22 AA24 AA33 AA33X AA77 AA86 AF23 AF23Y AF30 AF31 AF31Y AG32 AH19 BA01 BA03 BB01 BB05 BB06 BB12 BC01 BC03 4J002 BC031 BD031 BG051 BN122 FA082 GP00 4J026 AA45 AA14 DB07 GA07 DA07

Claims (8)

[Claims] An acrylic aggregate obtained by aggregating acrylic fine particles, wherein the acrylic fine particles have at least one inner layer made of an acrylic polymer having a glass transition temperature (Tg) of 0 ° C. or less. And the proportion of the acrylic fine particles in the whole is 1% by mass or more and 5% by mass or less, and Tg is 5% by mass or less.
An acrylic aggregate comprising an outermost layer made of an acrylic polymer at 0 ° C. or higher. 2. The acrylic according to claim 1, wherein the mass average particle size of the acrylic fine particles is 1 μm or more and 5 μm or less, and the mass average particle size of the acrylic aggregate is 100 μm or more and 1000 μm or less. Aggregates. 3. The method according to claim 1, wherein the acrylic fine particles are produced by a seed polymerization method.
The acrylic aggregate according to the above. 4. A light diffusing agent comprising the acrylic aggregate according to claim 1. 5. A light diffusing resin composition comprising 100 parts by mass of a transparent resin and 1 to 30 parts by mass of the light diffusing agent according to claim 4. 6. The absolute value of the difference between the refractive index of the acrylic polymer constituting the inner layer and the refractive index of the transparent resin contained in the acrylic fine particles is 0.01 to 0.1.
The light diffusing resin composition according to claim 5, wherein: 7. An Izod impact strength of 2000 J / m ²
A molded article comprising the light diffusing resin composition according to claim 5 or 6, characterized in that: 8. A molded article comprising the light diffusing resin composition according to claim 5, wherein a 50% breaking height is 0.19 m or more.