JPH0570600A - Resin particles and preparation thereof - Google Patents

Abstract

PURPOSE:To provide a sharp particle distribution of a resin by microdispersing a specific resin in an aq. medium and eliminating ionic groups present at the terminals thereof. CONSTITUTION:A resin comprising as the main component a polymer having ionic groups incorporated via ester bonds into the terminals of a polymer compd. is dissolved in an ambiphilic solvent. Water is added to the resulting soln. to microdisperse the same to obtain a liq. dispersion having a concn. of 5 to 500 milliequivalents/1,000 g and a particle size of 0.01 to 1.0mum. This liq. dispersion is heated in an alkaline or acidic region to eliminate the ionic groups present at the terminals of the microdispersed resin particles to coalesce the microdispersed resin to thereby obtain resin particles having an average particle size (D) of 0.1 to 100mum and including at least 70wt.% resin particles falling in the range of 0.5 to 2.0 D.

Description

Detailed Description of the Invention

[0001]

The present invention is widely used as a matting agent, an anti-blocking material, a chromatography carrier, a drug carrier, a powder coating, a gap adjusting material, an electrophotographic toner, cosmetics and the like. The present invention relates to a method for producing resin particles that has been developed.

[0002]

2. Description of the Related Art Conventionally, a "polymerization granulation method" can be exemplified as a method for obtaining resin particles used for such an application. The polymerization granulation method can be roughly classified into an emulsion polymerization method, a suspension polymerization method, a seed polymerization method, and a dispersion polymerization method.

In the emulsion polymerization method, resin particles are obtained by polymerizing in water in a micelle of a polymerizable monomer stabilized with a surfactant. In the emulsion polymerization method, particles having a sharp particle size distribution can be obtained. However, since the particle size is determined by the size of micelles that can stably exist, the particle size is limited to the range of about 0.01 to 0.5 μm, and about 1 μm.
It is impossible to obtain particles having a particle size of m or more. Further, the surfactant, which is essential for the stabilization of micelles, remains on the surface of the produced particles, so that the range of use of the obtained resin particles is limited.

The suspension polymerization method is a method of polymerizing the polymerizable monomer in a suspension system obtained by mechanically stirring water and the polymerizable monomer to obtain particles. In the suspension polymerization method, it is difficult to obtain polymer particles having a sharp particle size distribution because the particle size depends on mechanical stirring. The particle size range of the particles obtained by the suspension polymerization method is about 10 μm or more.

In the seed polymerization method, particles obtained by other methods are used as seed particles, the seed particles are swollen with a solvent and a polymerizable monomer, and the seed particles are grown large by polymerizing in the swollen seed particles. It is a method to let. In the seed polymerization method, in principle, particles having a sharp particle size distribution can be obtained by selecting appropriate seed particles, and the particle size of the particles is the same as the seed particles and the polymerizable monomer. It can be controlled by the swelling ratio with the body. In the seed polymerization method, particles obtained by the emulsion polymerization method, that is, vinyl polymer particles are used as seeds. It is difficult to swell vinyl polymer particles with a polymerizable monomer. The swelling ratio is determined by the balance between the interaction between the polymer forming the seed particles and the monomer used for swelling, the interfacial tension of the swollen particles, and the like, and actually the limit is about 2 to 10 times.
That is, the swelling rate cannot be extremely increased, and the particle size range in which the particles can be grown at one time is naturally limited. Since increasing the particle size by 10 times corresponds to increasing the volume by 1000 times, it is necessary to repeat seed polymerization in order to realize this in seed polymerization. The two-step swelling seed polymerization method is a method devised to increase the swelling rate of seed particles. In the two-step swelling seed polymerization method, first, the seed particles are swollen with an oligomer or a poorly water-soluble low molecular weight substance (: swelling agent) or the like, and then swollen with a polymerizable monomer. By this method, the swelling rate of the seed particles can be increased up to several thousand times. However, since the swelling agent remains in the particles obtained by the two-step swelling seed polymerization method, a step of removing them is essential. Although the seed polymerization method and the two-step swelling seed polymerization method are excellent methods in the sense of producing micron-order resin particles having a sharp particle size distribution, the above problems make the seed polymerization method industrially feasible. Making it difficult.

The dispersion polymerization method comprises a polymerizable monomer, an initiator,
This is a method in which a stabilizer is dissolved in an organic solvent and polymerization is initiated to grow polymer particles insoluble in the organic solvent, using the aggregates of oligomers generated in the initial stage as particle nuclei. Although the dispersion polymerization method is an excellent method for the purpose of producing resin particles of a micron order having a sharp particle size distribution, it is difficult to make a mass product because an organic solvent is used as a medium, and as an industrial production method of resin particles. Cannot be established.

The above-mentioned "polymerization granulation method", that is,
The resin particles produced by emulsion polymerization, suspension polymerization, seed polymerization, and dispersion polymerization are limited to "vinyl polymer" particles, as is obvious from the production method. With such a method, it is not possible to obtain resin particles of a condensation polymer represented by, for example, polyester and polyamide. A spray drying method, a salting-out method, a solvent removal method, a dispersion shaping method and the like have been proposed as a method for producing resin particles that is not limited to the type of resin.

The spray drying method is a method for obtaining particles by spray drying an emulsion or solution of a resin. The particle size of the particles obtained can be controlled to some extent by controlling the concentration of the emulsion or solution and the size of the fog droplets formed during spray drying. However, it is difficult to make the sizes of the mist droplets perfectly uniform, and coalescence of mist droplets occurs, so that the particle size distribution of the obtained particles becomes broad.

[0009] The salting-out method is a method in which a resin dissolved in a solvent is extruded into a system in which the resin is insoluble to deposit the resin to form particles. According to this method, the average particle size can be controlled to some extent by the concentration of the solution. However, since the size of each particle depends on the mechanical condition after ejection, the particle size distribution must be broad to some extent.

The solvent removal method is a method of mechanically suspending a solution of a resin dissolved in an organic solvent in water and gradually evaporating the organic solvent to obtain resin particles. With this method, it is difficult to obtain fine resin particles having a uniform particle size distribution because the particle size depends on mechanical stirring as in the suspension polymerization method.

The dispersion shaping method is a method in which a resin is crushed, and then crushed particles are dispersed in a non-solvent of the resin, and a sphere is formed by applying a temperature higher than the softening temperature of the resin. However, it is difficult to disperse fine powder in water, and a dispersant, a suspension stabilizer and the like are essential. Since these remain on the surface of the produced particles, the use range of the obtained resin particles is limited. Since the crushed resin has an irregular shape, it is difficult to make the particle diameters uniform by spheronization, and the particle diameter distribution becomes broad due to the secondary aggregation of the resin particles generated in the non-solvent. In order to suppress the secondary agglomeration of the resin particles, the concentration of the resin particles in the dispersion medium must be lowered, and in addition to the difficulty of the dispersion of the resin particles described above, it is necessary to establish this method industrially. Making it difficult.

[0012]

SUMMARY OF THE INVENTION As described above, the conventional method for producing resin particles produces resin particles having a sharp particle size distribution that is largely dependent on the type of resin. It was difficult to manufacture industrially.

[0013]

In view of such circumstances, the inventors of the present invention industrially manufacture resin particles having a sharp particle size distribution, having an arbitrary particle size, and independent of the type of resin. As a result of earnest research to find a method,
The next invention has been reached. That is, according to the present invention, the average resin particle size is 0.1 to 100 μm, which contains at least a polymer having a group having an ionic group through an ester bond at the end of a polymer compound, and has an average resin particle size of 0.5D. ~ 2.
The resin particles are characterized in that 70% by weight or more of particles are present in the range of 0D, and the main component is a polymer having a polymer compound containing an ionic group through an ester bond at the end thereof. The resulting resin is microdispersed in an aqueous medium, and in the microdispersion system, the ionic groups present at the terminals are cut off to combine the microdispersed resins, and the average particle diameter (D) is 0.1 to 0.1. 100 μm,
The method for producing resin particles is characterized in that the particles falling within the range of 0.5D to 2.0D are 70% by weight or more of the whole resin particles.

Since the object of the present invention is to provide a method for producing resin particles which does not depend on the type of resin, the type of resin is not limited at all, and vinyl type resins such as styrene type and acrylic type resin, It can be applied to all kinds of resins that can be dispersed in water by introducing an ionic group, such as polyester-based or polyamide-based condensed resins or epoxy resins.

However, the significance of the present invention is exerted by applying it to an area where a method for producing resin particles having a sharp particle diameter molecule is not established industrially, that is, to a condensation resin such as a polyester resin or a polyamide resin. To be done. In particular, as the polyester resin, either a saturated polyester resin or an unsaturated polyester resin can be used. The polyester resin preferably comprises a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid and 1,5-naphthalic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid and p- (hydroxyethoxy) benzoic acid. Acids, succinic acid, adibic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and other aliphatic dicarboxylic acids, fumaric acid, maleic acid, itaconic acid, hexahydrophthalic acid, tetrahydrophthalic acid, and other unsaturated aliphatic acids, and , Alicyclic dicarboxylic acid and the like can be used. If necessary, trimellitic acid, trimesic acid,
A small amount of tri- and tetracarboxylic acids such as pyromellitic acid may be contained. Examples of the glycol component include ethylene glycol, propylene glycol, 1,3-brovandiol, 1,4-butanediol, 1,5-bentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol. , 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, spiroglycol, 1,4-phenyleneglycol, 1,4
An ethylene oxide adduct of phenylene glycol,
Dimethylol heptane, tricyclodecane diol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and other diols, bisphenol A ethylene oxide adducts and propylene oxide adducts, hydrogenated bisphenol A ethylene oxide adducts and propylene oxide adducts Etc. can be used. In addition to these, a small amount of triols such as trimethylolethane, trimethylolpropane, glycerin, and ventaerythritol and tetraols may be included, if necessary. Further, as the polyester polyol, lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone may be included. Among the polyester-based resins, a resin particularly preferably used is one in which an aromatic polyvalent carboxylic acid is used as an acid component and an aliphatic and / or alicyclic polyhydric alcohol is used as an alcohol component.

The ionic group contained in the resin has a function of stably dispersing the resin in the aqueous medium. What is stable dispersion?
It means a state of being dispersed in an aqueous medium by the action of an electric double layer formed by dissociation of an ionic group contained in the resin itself. As the ionic group contained in the resin, a carboxyl group, a sulfonic acid group, a sulfuric acid ester group, a phosphoric acid group, or salts thereof (hydrogen salt, metal salt,
(Ammonium salt) group or anionic group, or a primary to tertiary amine group or other cationic group, preferably a carboxyl group, a carboxylate ammonium base,
Sulfonic acid groups, sulfonic acid alkali metal bases and the like can be used. In the present invention, these ionic groups are mainly introduced at the terminal of the polymer through an ester bond. These ionic groups are other groups such as alkylene groups,
It is introduced at the end of the polymer through a benzyl group, a ferulene group, or the like, or through an ester bond.

Particularly, as the ionic-containing compound capable of introducing an ionic group at the terminal of the polyester, parasulfobenzoic acid, metasulfobenzoic acid, orthosulfobenzoic acid, compounds of these metal salts, trimellitic acid, etc. Can be illustrated. Among these, more preferable are metasulfobenzoic acid and parasulfobenzoic acid, and particularly preferable is metasulfobenzoic acid. In the present invention, it is an essential requirement to introduce an ionic group at the polymer terminal, but it is acceptable to further contain the ionic group in the form existing in the chain copolymerized with the resin. As the ionic group-containing compound copolymerizable with the polyester resin, as the sulfonic acid metal group-containing compound, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4
-Metal salts such as sulfophthalic acid, 4-sulfonaphthalene-2,7 dicarboxylic acid and 5 [4-sulfophenoxy] isophthalic acid, and 2-dimethylaminomethyl, 2-methyl 1,3 propanediol as the amino group-containing compound. Etc. can be given. As the metal salt, Li, Na, K,
Examples thereof include salts of Mg, Ca, Cu, Fe and the like, and particularly preferable is Na salt.

These ionic groups are essential for the stable dispersion of the resin in the aqueous medium. The content of the ionic group is arbitrarily set within the range in which the target resin can be dispersed in water, but is generally 5 to 500 with respect to the resin.
meq / 1000 g, preferably 10-300 meq /
1000 g, more preferably 20-200 meq / 1
The range is 000 g. If the ionic group content is less than the lower limit, it may be difficult to microdisperse the resin in the aqueous medium. If the upper limit is exceeded, the resin may become soluble in water. The micro dispersion is a dispersion having an average particle size of 0.5 μm or less.

The method of microdispersing the resin containing an ionic group in an aqueous medium is not particularly limited. For example, the resin is once dissolved in an alcoholic, cellosolve-based, or ketone-based bipolar solvent and water is then added thereto. How to add,
Examples thereof include a method of directly adding hot water to the heat-melted resin and a method of previously mixing water and an amphoteric solvent and adding the resin to the resin. The resin introduced with an ionic group in the present invention has a self-emulsifying action and therefore is rapidly microdispersed. The particle size of the micro-dispersed particles takes a value between about 0.01 μm and 1.0 μm, but in the present invention, it is approximately 0.05 to 0.
It is preferable to adjust the microdispersion step and the ionic group content of the resin so that the particle diameter is about 5 μm.

The microdispersed particles of the ionic group-containing resin produced in this manner have an electric double layer formed on the surface thereof by dissociation of the ionic groups possessed by the resin itself, and have extremely stable dispersibility. I have.

Even if the micro-dispersed particles are taken out by drying, they are aggregated due to their small particle size, and it is impossible to take out individual particles as independent powders, which is extremely industrially useful. It will be limited. It has been attempted to appropriately agglomerate the micro-dispersed particles by causing an aggregating agent or the like to act on the aqueous dispersion of such a resin to form resin particles having a certain size. Since it cannot be generated uniformly, the obtained resin particles have a broad particle size distribution. In the present invention, the electric double layer is destroyed by an external environmental element such as a coagulant and the microdispersed particles are not aggregated, but the ionic groups themselves present on the surface of the microdispersed particles are cut off from the resin. It is characterized in that the dispersion stability of the micro-dispersed particles is deteriorated and the plurality of micro-dispersed particles are united to grow the particles.

There is no particular limitation on the method of cutting the ionic group from the resin, but it is preferable to heat the ionic group in an alkaline or acidic environment to remove one of the ionic groups and the polymer containing the ionic group. A method of hydrolyzing a part is preferable. The method of operating the pH of the system is not particularly limited, but an electrolyte having a buffering effect to some extent to avoid a sudden change in pH, for example, acetic acid and an ammonium cation such as dimethylamine, trimethylamine, dimethylaminoethanol, or an alkali. It is desirable to control the pH in the form of using metal ions together.
At this time, a hydrolysis catalyst may be used together. As a hydrolysis catalyst, a carboxyl group or a sulfonic acid group,
Or the compound containing the group of those salts can be illustrated. In the present invention, in particular, since the ionic group is introduced into the polymer terminal through an ester bond, the ionic group can be relatively easily cleaved by these operations.

The microdispersed particles from which the ionic groups have been cut off become unstable in dispersibility because the ionic group density on the surface decreases. Therefore, the particles are aggregated and coalesced with other particles, but the specific surface area of the resin particles is decreased by the coalescence, so that the ionic group density on the particle surface is increased (returned to the original) and the dispersion stability is restored again. The stabilization of redispersion by the coalescence of a plurality of particles is the most characteristic effect of the present invention. That is, in a system in which the dispersion stability has been destroyed due to external environmental factors such as the introduction of a flocculant, the once broken dispersion stability does not return to the original state, and aggregation proceeds transiently. Therefore, agglomeration and coalescence of particles proceed until agglomeration and separation of agglomerates are balanced by mechanical action such as stirring, and the resulting particle size distribution of the particles depends on the mechanical environment. However, in a system in which the dispersion stability once collapsed is re-stabilized by the coalescence of particles, the aggregation of particles does not proceed indefinitely, but the ionic groups are not cleaved and proceed depending on the degree. Therefore, it is possible to easily limit the particle size of the resin particles obtained by the amount of cutting off the ionic group and the speed thereof, and the particle size distribution becomes extremely sharp. Further, in the present invention, since the ionic group is mainly introduced at the polymer terminal, the change in the molecular weight due to the cutting of the ionic group is suppressed to the minimum, and it is easy to control the physical properties of the intended resin particles. Becomes

It is difficult to unconditionally limit the amount of the ionic groups cleaved off because it depends on the particle size of the initial micro-dispersed particles and the particle size of the desired resin particles, but the particles of the initial micro-dispersed particles are difficult to determine. Assuming that the diameter is 0.1 μm and the target particle diameter is about 1 to 10 μm, this corresponds to cutting off 10 to 50% of the initial ionic group content. The particles of the present invention have an average diameter of 0.1 to 100 μm, preferably 1 to 20 μm. Further, particles having an average diameter D of 0.5 to 2.0D are 70% by weight or more, and preferably 80% by weight.
It is at least wt%, more preferably at least 85 wt%.

In order to realize the redispersion stability by coalescence, the specific surface area of the resin particles must be reduced by the coalescence, that is, the resin particles must be spheroidized. Therefore, the environment in which the ionic group is cleaved is preferably such that the resin is in a plasticized state to some extent. The plasticization of the resin is realized, for example, by introducing a solvent or the like, or by simply raising the environmental temperature above the softening point of the resin.

It should be noted that other dispersion stabilizers are added to the particles in order to prevent unnecessary aggregation of the particles until the particles lose their stability due to the cutting off of the ionic group and are re-stabilized by coalescence and spheronization. It can be installed in. Dispersion stabilizers having such an action include, for example, a formalin condensate of naphthalene sulfonate, a polystyrene sulfonate,
Polyacrylic acid or a salt thereof, polyvinyl alcohol, and other known commercially available dispersants having a protective colloid action can be used.

The obtained resin particles are taken out as a dry powder according to a conventional method such as filtration, freeze drying, spray drying and the like.
In the aqueous medium at the time of coalescing growth of resin particles, other dispersions, for example, pigments, carbon flakes, silica, inorganic particles such as talc, or by coexisting with polymer particles or the like, these to coalesce growth of resin particles Accordingly, it can be incorporated into the particles. These can be appropriately added for the purpose of imparting coloring or hiding properties to the resin particles, and further imparting other functionality, within a range not impairing the stability of the dispersion. Further, the resin particles obtained according to the present invention have excellent dispersion stability in an aqueous medium, and therefore, dye coloring is easy. The resin particles in the present invention can be easily colored in high concentration with a disperse dye, vat dye, acid dye, basic dye or the like. Examples are shown below,
The present invention will be described in more detail, but the present invention is not limited thereto.

[0028]

Example 1 In an autoclave equipped with a thermometer and a stirrer, dimethyl terephthalate 95 parts by weight dimethyl isophthalate 95 parts by weight metasodium sulfobenzoic acid methyl ester 5 parts by weight ethylene glycol 40 parts by weight Ethylene oxide adduct of bisphenol A (Average molecular weight 350) 175 parts by weight Tetraptoxy titanate 0.1 part by weight was charged and heated at 180 to 230 ° C. for 120 minutes to carry out a transesterification reaction. Then, the reaction system was heated to 250 ° C., and the reaction was continued for 60 minutes at a system pressure of 1 to 10 mmHg, and as a result, a copolyester resin (A1) was obtained.
The obtained copolyester resin (A1) had a number average molecular weight of 4,500, a glass transition temperature of 63 ° C., and the composition was analyzed by NMR. As an acid component, terephthalic acid 48.9 mol% isophthalic acid 48.8 mol% metasodium sulfobenzoic acid was used. Acid 2.3 mol% As an alcohol component, it was ethylene glycol 58.4 mol% and ethylene oxide adduct of bisphenol A 43.6 mol%. Further, the content of sodium sulfonate group was 92 m equivalent / kg from the determination of S.

100 parts by weight of the copolyester resin (A1) and 30 parts by weight of butyl cellosolve were dissolved at 110 ° C., and then 200 parts of water at 80 ° C. was added, and the particle diameter was about 0.1 μm.
An aqueous microdispersion of the copolyester resin of m was obtained. Further, the obtained water-based microdispersion was put into a distillation flask and distilled until the distillation temperature reached 100 ° C. After cooling, water was added to make the solid content concentration 30%. To a four-necked 1 liter separable flask equipped with a thermometer, a condenser, and a stirring blade, 220 parts by weight of the aqueous copolymer polyester microdispersion and 2.0 parts by weight of acetic acid were added, and then dimethylaminoethanol was added to the system. PH was 9.5. Then, the temperature was raised to 85 ° C. and stirring was continued for 120 minutes. As a result, the micro-dispersed particles having a particle diameter of 0.1 μm, which were present in the aqueous dispersion of the copolyester, grew as a united particle, and when the average particle diameter was 5.3 μm and the diameter was D, it was 0.5.
Occupancy rate of particles having a particle size in the range of D to 2D is 95 wt%
To obtain polyester resin particles. The sodium sulfonate group content of the obtained polyester particles is 50 m equivalent / k
g, and about 40% of the initial ionic groups were cleaved. Furthermore, the supernatant liquid obtained by filtering the polyester resin particles was analyzed, and as a result, sodium sulfobenzoic acid was detected.

[0030]

Example 2 In an autoclave equipped with a thermometer and a stirrer, dimethyl terephthalate 136 parts by weight dimethyl isophthalate 53 parts by weight parasodium sulfobenzoic acid methyl ester 6 parts by weight ethylene glycol 24 parts by weight 1,4 butanediol 31 parts by weight Parts Cyclohexanedimethanol 60 parts by weight Tetraptoxytitanate 0.1 parts by weight was charged and the polymerization was carried out in the same manner as in Example 1 to obtain a copolyester resin (A2). The obtained copolyester resin (A2) had a number average molecular weight of 4,200, a glass transition temperature of 64 ° C., and a composition as a result of NMR analysis. As an acid component, terephthalic acid 69.8 mol% isophthalic acid 27.7 mol% parasodium sulfobenzoic acid was used. Acid 2.5 mol% As an alcohol component, it was ethylene glycol 31.5 mol% 1,4 butanediol 28.3 mol% cyclohexanedimethanol 40.2 mol%. Further, the content of sodium sulfonate group was 87 m equivalent / kg from the determination of S.

The copolyester resin (A2) was made into an aqueous microdispersion in the same manner as in Example 1. thermometer,
To a four-necked 1 liter separable flask equipped with a condenser and a stirring blade, 220 parts by weight of the obtained copolyester water-based microdispersion and 4.0 parts by weight of acetic acid were added, and then dimethylaminoethanol was added to the system. pH to 1
It was set to 1.4. Then, the temperature was raised to 90 ° C. and stirring was continued for 120 minutes. As a result, the micro-dispersed particles having a particle size of 0.1 μm existing in the copolyester aqueous dispersion were coalesced and the average particle size was 12.4 μm, and when the diameter was D, particles in the range of 0.5D to 2D. Polyester resin particles having a diameter occupancy of 87 wt% were obtained. The sodium sulfonate group content of the obtained polyester particles was 37.
It was m equivalent / kg, and about 60% of the initial amount of ionic groups had been cut off. Furthermore, the supernatant liquid obtained by filtering the polyester resin particles was analyzed, and as a result, sodium sulfobenzoic acid was detected.

[0032]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to industrially produce resin particles having an arbitrary average particle diameter and a sharp particle diameter distribution, and in principle, the molecular weight of the raw material polymer is not lowered. In addition, it is extremely useful as a method for producing resin particles that does not depend on the type of resin.

Claims (2)

[Claims] 1. An average resin particle diameter of 0.1 to 1 containing at least a polymer compound in which a group having an ionic group through an ester bond is contained at the terminal of the polymer compound.
A resin particle having a particle size of 00 μm and 70% by weight or more of particles in the range of 0.5D to 2.0D. 2. A resin containing a polymer as a main component, which contains a group having ionicity through an ester bond at the end of the polymer compound, is microdispersed in an aqueous medium, and in the microdispersion system, By cutting off the ionic group present at the terminal, the microdispersed resin is united, and the average particle diameter (D) is 0.1 to 100 μm, and 0.5D to
A method for producing resin particles, characterized in that 70% by weight or more of all particles falling within the range of 2.0D are resin particles.