JP6862772B2 - Method for producing porous polyurethane particles - Google Patents

Description

The present invention relates to a method for producing a polyurethane resin containing a water-soluble porogen. More specifically, the present invention relates to a method for producing polyurethane porous particles having a sharp pore size distribution in a wide particle size range by adding a polyurethane reaction solution to a porogen in a stirred state in a stirring device. In the present invention, it is not necessary to use a large-scale facility such as an extruder, and the preparation can be performed with a simple stirring device, so that the manufacturing cost can be significantly reduced. Furthermore, since the obtained polyurethane porous particles do not contain additives such as a defoaming agent, they are most suitable for the life science field and the food field where high safety is required.

As a method for obtaining a porous polyurethane resin, a method of foam molding a so-called polyurethane foam has been widely known. Polyester-based polyols and polyether-based polyols are mainly used in combination with aromatic isocyanates such as MDI (methylene diphenyl diisocyanate) and TDI (toluene diisocyanate) to provide heat insulating materials (hard polyurethane foam) and cushioning materials (soft polyurethane foam). Manufactured. Polyurethane foam is generally used in combination with an auxiliary agent such as a tertiary amine catalyst, a silicone defoaming agent, or a thickener in order to realize a high foaming ratio and high moldability. (Patent Document 1)

As another method for obtaining a polyurethane resin porous body, a polyurethane solution using a water-soluble polar solvent such as DMF (N, N-dimethylformamide) as a solvent is put into a poor solvent (mainly water) to make microporous. A so-called wet method (phase-separated molding method) for molding a plastic resin is known as a molding method for artificial leather and foam rolls (Patent Document 2).

In addition to this, a method of molding a non-woven fabric (web) as a polyurethane resin porous body has been known for a long time (Patent Document 3).

Further, a method of obtaining a polyurethane resin porous body by extruding a polyurethane solution containing a pore-forming material (porogen) and then immersing it in water to elute and remove the pore-forming material at the same time as gelation is also known. There is (Patent Document 4).

In the case of polyurethane foam, it has not yet been realized to completely suppress the bleed-out of the auxiliary agent used during molding, for example, the odor inside a new car or the odor of amine from a new sofa or bed, etc. This is an experienced phenomenon. Furthermore, aromatic isocyanates such as MDI and TDI are used in general polyurethane foams, and urethane bonds in the molecule may be hydrolyzed after long-term use to generate aromatic amines that are toxic to the human body. It is known (Patent Document 5).

Further, in the case of the polyurethane resin porous body molded by the wet method (phase separation molding method) of Patent Document 2, the water-soluble polar solvent (DMF, etc.) dissolved in the resin is completely removed even after the molded product is sufficiently washed with water. It is difficult to remove this residual solvent, and there is concern that this residual solvent is one of SVHC (substance of very high concern) in artificial leather sheets and the like.

The non-woven fabric mentioned in the prior art 3 is divided into several molding methods, and among them, the non-woven fabric molded by the mainstream dry spinning method or wet spinning method has a problem of residual solvent as described above.

The molded product of the prior art 4 has a sheet shape, and porous particles cannot be obtained. Further, as described above, it is very difficult to avoid residual solvent in the molded product.

Since MDI is used in most of the prior arts 2 to 4, the production of aromatic amines during long-term use poses a safety problem as in the case of foam.

Japanese Unexamined Patent Publication No. 2015-127395 Japanese Unexamined Patent Publication No. 4-264144 Japanese Unexamined Patent Publication No. 52-81177 Japanese Unexamined Patent Publication No. 2006-152177 Japanese Unexamined Patent Publication No. 7-224141

An object of the present invention is to provide a highly safe method for producing porous polyurethane particles, which is optimal for the life science field and the food field. The porous particles are polyurethane resins containing porogen before eluting the water-soluble porogen, and become polyurethane porous particles by eluting the porogen. The polyurethane porous particles obtained in the present invention are characterized in that the particle size can be set arbitrarily, the particle size distribution is narrow, and the pore size distribution is sharp.

As a result of diligent research to achieve these objectives, the present inventors put a water-soluble porogen in a stirring state in a stirring and mixing device, and a small amount of a solvent-free polyurethane resin reaction solution is added thereto. It was found that by supplying them one by one, porogen adheres to the droplets of the polyurethane reaction solution, and eventually polyurethane particles containing porogen are obtained. Further, after the polyurethane particles are cured, the porous particles can be obtained by eluting the porogen from the particles, as well as the design of the stirring and mixing device, the amount of porogen charged, the stirring speed, the amount of the polyurethane reaction solution supplied, and the amount of the polyurethane reaction liquid supplied. We have found that the above-mentioned series of problems can be solved by adjusting the supply rate to the optimum range, and have completed the present invention.
That is, the present invention is shown in the following [1] to [6].

[1] In a mixer having a rotary stirring blade, the reaction solution of the solvent-free polyurethane resin (A) is added in a state where the porogen (B) dissolved in water is agitated, and the polyurethane resin particles containing the porogen are mixed. In the manufacturing method
(1) Using a mixer in which the diameter (p) of the stirring blade is 60% or more of the inner diameter of the mixer,
(2) A method for producing a polyurethane resin, which comprises adjusting the stirring speed so that the peripheral speed of the tip of the stirring blade is 6.0 m / s or more and 15.0 m / s or less.

[2] Polygen (B) is polyvinyl alcohol (sakenization degree 70% or more and less than 98%), polyethylene glycol having an alkoxylated terminal, water-soluble cellulose derivative, polyacrylamide, polymethacrylamide, sodium chloride, potassium chloride, The method for producing a polyurethane resin according to [1], which comprises a single substance or a combination of two or more kinds selected from the group consisting of polysaccharides.

[3] The method for producing a polyurethane resin according to [1] or [2], wherein the average particle size of Porogen (B) is 5 μm or more and less than 900 μm.

[4] The polyurethane according to any one of [1] to [3], wherein the index ε {(D90-D10) ÷ D50} of the particle size distribution of Porogen (B) is less than 2.00. Resin manufacturing method.

[5] Polyurethane resin (A)
Polyfunctional isocyanate compound (I) containing at least one (one) selected from the group consisting of aliphatic polyisocyanates and alicyclic polyisocyanates, and
High molecular weight polyol compound (P) containing at least one selected from the group consisting of polycarbonate-based polyols and polyether-based polyols,
The method for producing a polyurethane resin according to any one of [1] to [4], which is a reaction product of a chain extender (E) and a cross-linking agent (X).

[6] Porous particles having an average particle size of 400 μm or more and 3 mm or less, an average pore diameter of 5 μm or more and 900 μm or less, and a pore volume of 2.0 cm ^ 3 / g or more.

According to the method for producing porous polyurethane particles of the present invention, the porous polyurethane has a narrow particle size distribution, a sharp pore size distribution, excellent heat resistance and hydrolysis resistance, and high safety to the living body in a simple process. Particles can be obtained.

It is a figure which showed the outline of a mixer. It is a figure which showed an example of the stirring blade inside a mixer. It is a figure which showed the appearance of the polyurethane resin particle. It is a figure which showed the appearance of the polyurethane porous particle.

The present invention is at least
・ Using a rotary stirring and mixing mixer,
-Using a stirring blade having an effective length (p) of 60% or more with respect to the inner diameter (d) of the mixer,
・ Set the rotation speed (peripheral speed) of the tip of the stirring blade to 6.0 m / s or more and 15.0 m / s or less.
-Add water-soluble porogen (B) to a depth (h) of 2% or more and 30% or less with respect to the inner diameter (d) of the mixer.
-A solvent-free polyurethane resin (A) reaction solution was added to the agitated water-soluble porogen (B), and the mixture was added.
The present invention relates to a method for producing polyurethane resin particles containing porogen (B).
Further, it is possible to obtain polyurethane porous particles by eluting porogen from the polyurethane resin particles obtained by this production method.

According to the study of the inventor, by adjusting the design of the mixer for stirring and mixing, the amount of porogen (B) charged, the stirring speed, the supply amount and the supply speed of the solvent-free polyurethane resin (A) reaction solution, to the optimum range. It is possible to obtain polyurethane resin particles (and porous particles obtained by eluting them) having a narrow particle size distribution and a small variation in pore diameter.
Furthermore, by using a solvent-free polyurethane resin in which an aliphatic or alicyclic isocyanate compound (I) is combined with a polycarbonate-based or polyether-based polyol, it is excellent in hydrolysis resistance, heat resistance, and yellowing resistance. Polyurethane resin particles (and porous particles obtained by eluting them) can be obtained.

Further, in order to obtain porous particles having a sharp pore size distribution, it is a major premise to use a porogen having a narrow particle size distribution, and further, in a polyurethane resin under the condition that the shape of the porogen (B) is not deformed at the time of preparation. It is important to evenly disperse the porogen.

Hereinafter, the present invention will be described in detail.
First, the apparatus and granulation conditions will be described.

The stirring / mixing mixer has the ability to sufficiently stir Porogen (B). Further, it is important to select a stirring blade in order to realize uniform stirring while suppressing pulverization of Porogen (B).
The inner surface of the stirring mixer and the surface of the stirring blade are preferably made of stainless steel such as SUS316 or SUS304 in consideration of adhesion stains of the polyurethane reaction liquid, suppression of charge of the contents, and corrosion resistance.

Furthermore, it is necessary to take care to prevent the accumulation of particles inside the mixer as much as possible. In particular, the corners of the wetted parts must be rounded (corner rounded) to about 3 to 30% of the inner diameter of the mixer. desirable.
The stirring blade is preferably a turbine blade, a paddle type, or a blade blade, and more preferably a turbine blade or a blade blade.

The design of the stirring blade is not particularly limited, and known blades such as propeller type, paddle type, swept blade, turbine blade, blade blade, and anchor type can be used in combination of one or more stages. A blade with a large shearing force is preferable for uniform stirring and mixing, but on the other hand, a blade with a high shearing force also has a strong force for crushing porogen, so it is important to determine the balance.
The most important point in selecting a stirring blade in the present invention is the ratio of the effective length of the stirring blade to the inner diameter of the mixer.

The effective length (p) of the stirring blade must be 60% or more of the inner diameter (d) of the mixer, and if it is less than this value, a lump is formed between the inner surface of the mixer and the stirring blade during the preparation of the polyurethane resin particles. This makes it difficult to obtain particles. This value is preferably 65% or more, more preferably 70% or more.

The rotation speed of the stirring blade must be 6.0 m / s or more and 15.0 m / s or less as the peripheral speed of the tip of the stirring blade. If it is less than this value, the stirring of the porogen and the polyurethane resin tends to be non-uniform, and satisfactory polyurethane resin particles cannot be obtained. On the other hand, if it exceeds this value, the shearing force of the stirring blade becomes large, so that the shape of the polyurethane resin particles approaches a true sphere and becomes good. Further, since the pulverization of porogen is promoted by the excessive shearing force, the pore size distribution of the obtained polyurethane porous particles becomes large. The preferred range of peripheral speed is 6.5 m / s or more, 14.0 m / s or less, and more preferably 7.0 m / s or more and 13.0 m / s or less.

Considering the suppression of porogen pulverization, it is preferable that the stirring time of the mixer is short, and the stirring should be stopped at least within 10 minutes from the start of stirring. The stirring time is preferably within 7 minutes, more preferably within 5 minutes.
Optimal operating conditions vary depending on the brittleness and hardness of the porogen used, but granulation is completed at the fastest possible rotation speed that allows crushing of the porogen and in the shortest processing time in which the porogen is uniformly dispersed in the polyurethane resin. It is essential to let them produce good products.

The charging depth (h) of Porogen (B) inside the mixer before the start of stirring needs to be 2% or more and 30% or less with respect to the inner diameter of the mixer. It is preferably 2% or more and 25% or less, and more preferably 2% or more and 20% or less. If it is less than the lower limit, the amount of porogen is too small, so that the adhesion of the polyurethane reaction liquid to the wall inside the mixer and the stirring blade is relatively increased, and the polyurethane resin particles are different from the charging ratio. When the upper limit is exceeded, the convection of the upper and lower layers in the mixer is reduced, and there arises a problem that polyurethane resin particles having different compositions are unevenly distributed in the upper layer portion and the lower layer portion.

The charging ratio of the polyurethane resin (A) and the porogen (B) is in the range of (A) :( B) = 1.0: 5.0 to 1.0: 30.0 in terms of mass ratio. If the amount of porogen is too small, the mixing property in the mixer is lowered, and it becomes difficult to prepare satisfactory polyurethane resin particles. If the amount of pologene is too large, the polyurethane reaction solution is relatively insufficient, and not only the shape of the polyurethane resin particles becomes irregular, but also the pillars forming the porous particles become thin and the polyurethane porous particles become brittle. ..

In the present invention, in most cases, the reaction of the polyurethane resin (A) is not completed when it is taken out from the mixer. In many cases, the polyurethane resin particles taken out remain flexible and sticky, and after dusting the polyurethane resin particles with the used porogen as a dusting agent, the environment at 60 ° C to 120 ° C for about 2 to 5 days. By curing, the urethanization reaction can be completed while maintaining good shape of the particles themselves and the pores. Generally, the reaction rate of the two-component polyurethane can be determined by the peak intensity of the isocyanate group appearing at 2270 cm ^ -1 in the FT-IR spectrum, and it can be determined that the reaction is completed when the peak disappears.

The porogen for the dusting agent may be dusted after the particles are taken out, but before taking out from the mixer, the porogen is added into the mixer immediately after the uniform polyurethane resin particles are prepared, and it takes several seconds to several tens of seconds. It is preferable to mix for a short time and dust. At this time, in order to suppress the deformation of the polyurethane resin particles, it is desirable that the rotation speed (peripheral speed) of the stirring blade is 6.0 m / s or less.

Porogen (B) contained in the polyurethane resin particles is completely eluted in a water bath, a hot water bath, or the like, and then dried to obtain porous particles. The porous particles preferably have an average particle size of 400 μm or more and 3.0 mm or less, an average pore diameter of 5 μm or more and 900 μm or less, and a pore volume of 2.0 cm ^ 3 / g or more. More preferably, the average particle size is 450 μm or more and 2.5 mm or less, the average pore diameter is 7 μm or more and 500 μm or less, and the pore capacity is 2.5 cm ^ 3 / g or more.

Before elution of Porogen (B) from the polyurethane resin particles in which the reaction is completed, it is preferable to classify the porogen (B) as necessary and adjust the particle size to a predetermined size range. This is because the apparent specific gravity of the polyurethane porous particles after eluting the porogen becomes small, which makes the classification treatment using a sieve difficult.

When the polyurethane porous particles are used in water, the particles after elution of Porogen (B) can be stored in water without being dried. This is also effective in suppressing the floating of the porous particles due to the remaining air bubbles in the pores when the once dried porous particles are immersed in water again.

When applying porous particles to applications that require biocompatibility, it is desirable to sterilize them in advance. As a sterilization method, a known method can be used, and preferably, sterilization by immersing in ethanol having a concentration of 30% by volume or more, sterilization by an autoclave at 120 ° C., sterilization by gamma irradiation, and the like can be mentioned.

Subsequently, the raw materials used will be described.

The porogen (B) that can be used in the present invention is water-soluble, and is a polyvinyl alcohol (sakenization degree of 70% or more and less than 98%), polyethylene glycol having an alkoxylated terminal, and a water-soluble cellulose derivative (methyl cellulose, carboxymethyl cellulose, It is a single substance or a combination of two or more selected from the group consisting of sodium salt of carboxymethyl cellulose, hydroxypropyl methyl cellulose, etc.), polyacrylamide, polymethacrylicamide, sodium chloride, potassium chloride, and polysaccharides. Of these, water-soluble cellulose derivatives, sodium chloride, potassium chloride, and polysaccharides are preferable. Particularly preferred are sodium chloride, potassium chloride and polysaccharides. Most preferred are sodium chloride and potassium chloride.

The shape of the porogen (B) may be either particulate or fibrous, but its size (or diameter) is an important point. If this size is not uniform, the pores of the porous particles after elution of porogen from the polyurethane resin particles are likely to be uneven.

When the porogen (B) is in the form of particles, its average particle size is preferably 5 μm or more and less than 900 μm. More preferably, the average particle size is 7 μm to 500 μm, and most preferably the average particle size is 10 μm to 400 μm.

When the porogen (B) is in the form of particles, it is desirable that ε {(D90-D10) ÷ D50}, which is an index of the particle size distribution of the porogen (B), is less than 2.00. This particle size distribution can be measured by Microtrac HRA (manufactured by Nikkiso Co., Ltd., laser diffraction type particle size distribution meter, measured by wet circulation using a poor solvent for porogen) and the like.

The high molecular weight polyol compound (P) constituting the solvent-free polyurethane resin (A) may contain a polycarbonate-based or polyether-based polyol having an average number of functional groups of less than 3 and a number average molecular weight of 400 or more and 3000 or less. preferable.
The number average molecular weight of the polyol can be calculated from the hydroxyl value according to JIS K1557.
Further, the number average molecular weight of the polyol can be measured by converting it into polyethylene, polystyrene or the like using a gel permeation chromatograph (GPC).

Here, the "average number of functional groups" means a calculated value obtained from the hydroxyl value and the number average molecular weight.
The total amount of the polycarbonate-based polyol and the polyether-based polyol preferably occupies 75% or more of the high molecular weight polyol compound (P) in terms of mass ratio, more preferably 85% or more, and most preferably 95% or more.

Polycarbonate-based polyols are obtained by a known method of condensing a low molecular weight diol and a low molecular weight carbonate.

The low molecular weight diol is a compound having two or more active hydrogen groups and a number average molecular weight of less than 400, such as ethylene glycol, 1,2- or 1,3-propanediol, 1,2- or 1,3-butane. Diol, 1,4-butanediol (hereinafter abbreviated as 1,4-BD), 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, alkane (7-22) diol, diethylene glycol, triethylene Glycol, dipropylene glycol, 1,3- or 1,4-cyclohexanedimethanol and mixtures thereof, 1,4-cyclohexanediol, alkane-1,2-diol (C17-20), 3-methyl-1,5 -Pentanediol, 2-ethyl-1,3-propanediol, 2-normalpropyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2-normalbutyl-1,3-propanediol, 2-Isobutyl-1,3-propanediol, 2-terriarybutyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propane Diol, 2-ethyl-2-normalpropyl-1,3-propanediol, 2-ethyl-2-normalbutyl-1,3-propanediol, 2-ethyl-3-ethyl-1,4-butanediol, 2 -Methyl-3-ethyl-1,4-butanediol, 2,3-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2,3,4-triethyl-1, 5-Pentanediol, Dimethylolpropionic Acid, Dimethylolbutanoic Acid, Dimeric Acid Diol, alkylene Oxide Additives of Bisphenol A, Bisphenol F Hydrochloride, Bisphenol A Hydrochloride, 1,4-dihydroxy-2-butene, p-xylyl Lenglycol, bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) isophthalate, 1,4-bis (2-hydroxyethoxy) benzene, 1,3-bis (2-hydroxyethoxy) benzene, resorcin, Hydroquinone, 2,2'-bis (4-hydroxycyclohexyl) propane, 2,6-dimethyl-1-octene-3,8-diol, 3,9-bis (1,1-dimethyl-2-hydroxyethyl)- 2,4,8,10-Tetraoxaspiro [5,5] Undecane, Bisphenol F, Bispheno Examples thereof include dihydric alcohols such as Lu A, which can be used alone or in combination of two or more.

Examples of the low molecular weight carbonate include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, diaryl carbonates such as diphenyl carbonate, and alkylene carbonates such as ethylene carbonate and propylene carbonate.
The preferred number average molecular weight of the polycarbonate-based polyol in the present invention is 400 or more and 3,000 or less, more preferably 400 or more and 2,000 or less, and most preferably 400 or more and 1,000 or less. When the number average molecular weight increases, the viscosity of the liquid increases, the workability when preparing the polyurethane resin (A) decreases, the mixability with the polyfunctional isocyanate compound (I) deteriorates, and the reaction becomes non-uniform. Is likely to cause harmful effects.

Generally, a polyether polyol is obtained by adding an ethylene oxide or an alkylene oxide having 3 or more carbon atoms to an initiator using a low molecular weight active hydrogen compound alone or in a combination of a plurality of them using a Lewis acid catalyst or the like. is there. Examples of the "alkylene oxide having 3 or more carbon atoms" include 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, tetrahydrofuran (1,4-butylene oxide) and the like. In the present invention, ethylene oxide, propylene oxide, or tetrahydrofuran is preferable.

As the low molecular weight active hydrogen compound used as an initiator of the polyether polyol, in addition to the above low molecular weight diol, a low molecular weight polyol having three or more active hydrogen groups and a number average molecular weight of less than 400 is preferable, and glycerin and trimethylolpropane Trivalent alcohols such as (hereinafter abbreviated as TMP), polyhydric alcohols having four or more hydroxyl groups such as tetramethylolmethane, pentaerythritol, dipentaerythritol, D-sorbitol, xylitol, D-mannitol, D-mannit, etc. Low molecular weight polyamines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, tolylenediamine, diethyltrilenideamine, diaminodiphenylmethane, isophoronedimine, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine , N-methyl-diethanolamine, N-phenyl-dipropanolamine and other low molecular weight amino alcohols, and the above-mentioned low molecular weight polyamines and low molecular weight amino alcohols with alkylene oxide added, and the like, which are used alone or 2 It can be used in a combination of more than one species.

The number of functional groups of the initiator of the polyether polyol is preferably less than 4.0, more preferably less than 3.0. When the number of functional groups of the initiator exceeds the upper limit, the flexibility and toughness of the obtained polyurethane resin (A) are likely to be lost.

In the present invention, a polyester polyol can be used in combination with a part of the high molecular weight polyol compound (P) as long as the performance is not impaired. Examples of the polyester polyol include a polycondensate obtained by reacting a low molecular weight active hydrogen compound with a polybasic acid under known conditions.

Examples of the low molecular weight active hydrogen compound include the above-mentioned low molecular weight diols and low molecular weight polyols, which can be used alone or in combination of two or more.

Examples of polybasic acids include oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, 1,1-dimethyl-1,3-dicarboxypropane, 3-methyl-3-ethylglutaric acid, and azeline. Acids, sebatic acids, other aliphatic dicarboxylic acids (11 to 13 carbon atoms), suberic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, octadecanedioic acid, nonadecandioic acid, Eikosandioic acid, methylhexanedioic acid, citraconic acid, hydrogenated dimeric acid, maleic acid, fumaric acid, itaconic acid, orthophthalic acid, isophthalic acid, terephthalic acid, toluenedicarboxylic acid, dimeric acid, hetic acid and other carboxylic acids, and , Acid anhydrides derived from these carboxylic acids, acid halides, ricinoleic acid, 12-hydroxystearic acid and the like.

Specific examples of the polycondensate of a low molecular weight polyol and a polybasic acid include poly (ethylene butylene adipate) polyol, poly (ethylene adipate) polyol, poly (ethylene propylene adipate) polyol, poly (propylene adipate) polyol, and poly. Examples thereof include (butylene hexamethylene adipate) polyol, poly (butylene adipate) polyol, and poly (hexamethylene adipate) polyol.

Further, as the polyester polyol, polycaprolactone polyol, polyvalerolactone polyol, and further, obtained by ring-opening polymerization of lactones such as ε-caprolactone and γ-valerolactone using the low molecular weight polyol as an initiator. Examples thereof include a lactone-based polyol obtained by copolymerizing the divalent alcohol.

The chain extender (E) used in the present invention is a compound selected from the above-mentioned low molecular weight diols, and can be used alone or in combination of two or more.
In the present invention, the molar ratio to the high molecular weight polyol (P) is preferably 0.01 or more and 0.20 or less. If it is less than 0.01, the aggregation of urethane bonds, that is, the so-called hard segment domain is insufficient, and the strength and heat resistance of the polyurethane resin (A) are lowered. On the other hand, if the upper limit is exceeded, the hard segment domain becomes excessive, and the flexibility and toughness of the obtained polyurethane resin (A) are likely to be lost.

The cross-linking agent (X) used in the present invention is selected from the above-mentioned low molecular weight polyols (active hydrogen compounds having a trivalent or higher valence) alone or in combination of two or more, and has a molecular weight of 30 or more and 450 or less per functional group. Compounds are preferred, more preferably 40-400. Further, preferable active hydrogen groups of the cross-linking agent are hydroxyl groups and amino groups.
A particularly preferable one of the cross-linking agent (X) in the present invention is TMP.
In the present invention, the molar ratio to the high molecular weight polyol (P) is preferably 0.01 or more and 0.20 or less. If it is less than 0.01, the effect of using the cross-linking agent is not seen, and if it exceeds 0.20, the hard segment domain is excessive, and the flexibility and toughness of the obtained polyurethane resin (A) are likely to be lost. ..

In the present invention, it is desirable to use a urethanization catalyst in consideration of advantages such as shortening of the reaction time of the polyurethane resin (A) and completion of the reaction.
Any commonly used urethanization catalyst can be used as the catalyst, but so-called amine-based catalysts such as tertiary amines and quaternary ammonium salts have harmful effects due to residual catalysts in the resin (adverse effects on living organisms and odors). ) Is not preferable. Metallic catalysts are preferred, including bismuth, lead, tin, iron, titanium, zirconium, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese and calcium. Organic compounds such as, inorganic compounds and the like can be mentioned.
Among these, the most preferable ones are bismuth-based catalysts and zirconium-based catalysts.
The catalyst may be used alone or in the form of a mixture of two or more.
The amount of the catalyst used is determined by the properties of other raw materials, reaction conditions, desired reaction time, etc., and is not particularly limited, but is generally 0. It is preferably 001 to 0.05% by mass, and more preferably 0.002 to 0.02% by mass.

In addition, if necessary, lubricants, flame retardants, plasticizers, hydrolysis inhibitors, antioxidants, UV absorbers, colorants, various fillers, internal mold release agents, blocking inhibitors, reinforcing fibers, etc. Although it can be used by adding a processing aid, it is desirable to reduce the amount used as much as possible in consideration of bleeding out from the polyurethane resin (A) after molding. Among these auxiliaries, those having no active hydrogen group capable of reacting with isocyanate can be used by being mixed with the polyfunctional isocyanate compound (I) in advance.

As the polyfunctional isocyanate compound (I) used in the present invention, at least one selected from the group consisting of aliphatic isocyanates and alicyclic isocyanates is used, and each isocyanurate form or allophanate form can be contained.

Examples of the polyfunctional isocyanate compound (I) used in the present invention include hexamethylene diisocyanate (hereinafter referred to as HDI), tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, and 3-methyl-pentane-1,5-. Aliphatic diisocyanates such as diisocyanate, decamethylene diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate; aromatic aliphatic diisocyanates such as xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, tetramethylxylylene diisocyanate; isophorone diisocyanate (isophorone diisocyanate) (Hereinafter referred to as IPDI), norbornan diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, methylene dicyclohexyldiisocyanate (also known as hydrogenated diphenylmethane diisocyanate, hereinafter referred to as H12-MDI), alicyclic diisocyanate such as hydrogenated tetramethylxylene diisocyanate. , And the adduct form obtained by reacting the isocyanate trimmer form, allophanate form, biuret form, dimer form, dimer trimmer form, carbodiimide form, uretonimine form, bifunctional or higher-functional polyol and the like with the isocyanate form.

These organic isocyanates may be used alone or in the form of a mixture of two or more. In the present invention, an isocyanate selected from an aliphatic, aromatic aliphatic, and alicyclic type is preferable in consideration of the biosafety of the obtained polyurethane porous particles, and HDI, IPDI, or H12 is particularly preferable from the viewpoint of heat resistance and the like. -MDI is preferred. These organic diisocyanates have a high vapor pressure at room temperature, and in consideration of the working environment when preparing urethane resin, unreacted diisocyanates are used after adducting, trimming (isocyanurate), allophanate, biuret, etc. Distillation-removed ones are more preferable. These reactions may be used alone or in combination of two or more.

As a preferable form of the polyfunctional isocyanate compound (I) of the present invention, the organic isocyanate is adducted with the above-mentioned low molecular weight diol (divalent alcohol), the organic isocyanate is trimmed, or the organic isocyanate is made with a monohydric or higher alcohol. Isocyanateized, and then the unreacted isocyanate monomer component is distilled off. These reactions may be used alone or in combination of two or more.

The most preferable form of the polyfunctional isocyanate compound (I) of the present invention is that the organic isocyanate is adducted with the above-mentioned low molecular weight diol (dihydric alcohol) and then trimmerized, and the unreacted isocyanate monomer component is distilled off and removed. , The polyol is partially reacted to form a prepolymer.

As the polyol used for prepolymerization, the above-mentioned polyether polyol is preferable. Of these, polyethylene glycol (hereinafter abbreviated as PEG) is preferable.
The number average molecular weight of PEG is preferably 200 to 1,500, more preferably 300 to 1,000, and most preferably 400 to 800.

The amount of the polyether polyol introduced in the prepolymerization is preferably in the range of 1 to 20% with respect to the polyurethane resin (A) to be prepared. It is preferably 1 to 15%, more preferably 1 to 10%.
In the case of a prepolymer using PEG, when the introduction amount falls below the lower limit, the polyurethane resin (A) becomes cloudy white (reversible whitening, and becomes transparent when dried) under high temperature and high humidity (for example, during the elution operation of porogen). Back) There is a risk. On the other hand, when the introduction amount exceeds the upper limit, the viscosity of the polyfunctional isocyanate compound (I) increases, the workability when preparing the polyurethane resin (A) decreases, or the mixture with the high molecular weight polyol compound (P). It is easy for adverse effects such as worsening and non-uniform reaction to occur.

The method for producing polyurethane porous particles in the present invention and the produced porous particles will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the examples and comparative examples, "%" means "mass%".

<Preparation method of polyurethane resin particles>
(1) A high molecular weight polyol (P), a chain lengthing agent (E), a cross-linking agent (X), and if necessary, an auxiliary agent such as a catalyst are mixed in advance to adjust the temperature.
(2) Pologen (B) is sufficiently pre-dried to remove water to 0.1% or less.
(3) Porogen (B) is charged into a mixer for stirring and mixing equipped with a stirring blade, and purged with nitrogen gas.
(4) In another mixer, the polyfunctional isocyanate compound (I) and the polyol mix premixed in (1) are uniformly mixed.
(5) This mixed solution is sufficiently defoamed by a decompression operation or the like, and is dropped into the mixer at the same time as the stirring of the mixer charged with Porogen is started.
(6) Polyurethane resin particles in which the porogen (B) is attached to the polyurethane resin (A) in a coat shape can be obtained at a predetermined rotation speed and mixing time.
(7) Porogen (B) is added as a dusting agent according to the state of the polyurethane resin particles, and the particles are stirred at a low speed for several seconds to several tens of seconds to dust the particles.
(8) The obtained particles are placed in a sealed container and cured in an atmosphere of 90 ° C. for 2 days.
(9) Polyurethane resin particles can be obtained by classifying with a sieve having an arbitrary opening.

For mixing the above polyol mix and the polyfunctional isocyanate compound (I), a low-pressure injector equipped with a known mechanical agitator or a high-pressure injector using a high-pressure collision mixing method can be used.

The R value at this time ([total number of moles of isocyanate groups of the polyfunctional isocyanate compound] / [total number of moles of hydrogen groups in the polyol mix]) is preferably 0.70 or more and less than 1.30. It is more preferably 0.70 or more and less than 1.25, and further preferably 0.70 or more and less than 1.20.
The polyurethane resin particles thus obtained are spherical particles having a porogen on the outer surface as shown in FIG.

<Synthesis example 1>
995 g of HDI (manufactured by Tosoh, NCO content: 49.9% by mass), 1.0 g of phenol, 1,3- in a four-necked flask with a capacity of 1000 ml equipped with a stirrer, a thermometer, and a cooling tube. 5 g of butandiol (manufactured by Daicel Chemical Industries, Ltd., hereinafter referred to as 1,3-BG) was charged, and a urethanization reaction was carried out at 80 ° C. for 2 hours under a nitrogen stream. Then, the reaction solution was kept at 60 ° C., 0.5 g of a 20% diethylene glycol (manufactured by Adeka Corporation) solution of potassium octylate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the isocyanurate-forming reaction was carried out for 2 hours. After the NCO content reached 39.5% by mass, 0.3 g of 2-ethylhexyl acid phosphate (manufactured by Johoku Chemical Industry Co., Ltd., hereinafter referred to as JP-508) was added to carry out a termination reaction. The unreacted HDI was removed by thin-film distillation of this reaction solution at 130 ° C. × 0.04 kPa to obtain purified polyisocyanate (hereinafter referred to as PI) 1 in a yield of 37.1% by mass. PI-1 is a transparent viscous liquid having an NCO content of 21.8% by mass, a GPC number average molecular weight of 680, an average functional group number of 3.5 based on the formula (1), and an EO content (PEG content). The free HDI content was 0% by mass and 0.2% by mass. The average number of NCO functional groups was calculated from the formula (1).

Average number of NCO functional groups = NCO content x number of GPCs Average molecular weight / (100 x 42) ... (1)
<GPC: Measurement of number average molecular weight>
-Measuring instrument: HLC-8220 (manufactured by Tosoh Corporation)
-Column: TSKgel (manufactured by Tosoh)
・ G3000H-XL
・ G2500H-XL
・ G2000H-XL
・ G1000H-XL
-Carrier: tetrahydrofuran (THF)
-Detector: RI (refractive index) detector-Sample: 0.5% THF solution-Temperature: 40 ° C
-Flow velocity: 1.000 ml / min
・ Calibration curve: Standard polystyrene (manufactured by Tosoh)
F-80 (Molecular weight: 7.06 × 105, Molecular weight distribution: 1.05)
F-20 (molecular weight: 1.90 x 105, molecular weight distribution: 1.05)
F-10 (Molecular weight: 9.64 × 104, Molecular weight distribution: 1.01)
F-2 (Molecular weight: 1.81 × 104, Molecular weight distribution: 1.01)
F-1 (Molecular weight: 1.02 × 104, Molecular weight distribution: 1.02)
-A-5000 (Molecular weight: 5.97 × 103, Molecular weight distribution: 1.02)
-A-2500 (Molecular weight: 2.63 × 103, Molecular weight distribution: 1.05)
A-500 (Molecular weight: 5.0 × 102, Molecular weight distribution: 1.14)

<Synthesis example 2>
In the same reaction vessel as in Synthesis Example 1, 995 g of IPDI (manufactured by Ebonic, NCO content: 37.8% by mass), 1.0 g of phenol, and 5 g of 1,3-BG were charged, and the temperature was 80 ° C. under a nitrogen stream. The urethanization reaction was carried out for 2 hours. Then, the reaction solution was kept at 60 ° C., 0.5 g of a 20% diethylene glycol solution of potassium octylate was added, and the isocyanurate-forming reaction was carried out for 2 hours. After the NCO content reached 31.0% by mass, 0.3 g of JP-508 was added to carry out a termination reaction. A part of unreacted IPDI was removed by thin-film distillation of this reaction solution at 130 ° C. × 0.04 kPa to obtain purified PI-2 in a yield of 34.5% by mass. PI-2 is a transparent viscous liquid with an NCO content of 20.0% by mass, a GPC number average molecular weight of 700, an average functional group number of 3.3 based on formula (1), and an EO content (PEG content). The content was 0% by mass and the free IPDI content was 15.0% by mass.
When free IPDI was distilled off to 0.2% by mass by thin film distillation, a solid having an NCO content of 17.3% by mass and a melting point of 108 ° C. was obtained.

<Synthesis example 3>
In the same reaction vessel as in Synthesis Example 1, 900 g of PI-1 and 100 g of PEG-600 (polyoxyethylene glycol manufactured by Sanyo Chemical Industries, Ltd., terminal OH functional group number 2, number average molecular weight 600) were charged, and 80 g under a nitrogen stream. The urethanization reaction was carried out at ° C. for 5 hours to obtain PI-3. PI-3 was a transparent viscous liquid having an NCO content of 19.3% by mass, a GPC number average molecular weight of 795, and an average NCO functional group number of 3.6 based on the formula (1). The EO content (PEG content) is 10% by mass.

<Synthesis example 4>
In the same reaction vessel as in Synthesis Example 1, 850 g of PI-2 and 150 g of PEG-1000 (polyoxyethylene glycol manufactured by Sanyo Chemical Industries, Ltd., terminal OH functional group number 2, number average molecular weight 1000) were charged, and 80 g under a nitrogen stream. The urethanization reaction was carried out at ° C. for 5 hours to obtain PI-4. PI-4 was a transparent viscous liquid having an NCO content of 17.5% by mass, a GPC number average molecular weight of 815, and an average NCO functional group number of 3.4. The EO content (PEG content) is 15% by mass.

<Synthesis example 5>
In the same reaction vessel as in Synthesis Example 1, 500 g of 4,4'-diphenylmethane diisocyanate (Millionate MT manufactured by Tosoh Corporation, NCO content: 33.6 mass%, hereinafter referred to as MT) and 150 g of PEG-1000 were charged, and a nitrogen stream was charged. Below, the urethanization reaction was carried out at 80 ° C. for 5 hours. Then, 350 g of polyphenylene polymethylene polyisocyanate (Millionate MR-200 manufactured by Tosoh Corporation, NCO content: 30.8% by mass, hereinafter referred to as MR-200) was added and mixed uniformly to obtain PI-5. PI-5 was a brown transparent viscous liquid having an NCO content of 26.3% by mass, a GPC number average molecular weight of 355, and an average NCO functional group number of 2.2. The EO content (PEG content) is 15% by mass.

<Preparation Examples 1 to 4: Preparation of Porogen (B)>
Porogen (B) was prepared according to the formulation shown in Table 3.
For sodium chloride (hereinafter abbreviated as NaCl), Naclefor 5 (manufactured by Naikai Salt Industries Co., Ltd.) is appropriately classified with a predetermined sieve, and before use, it is dried in a hot air dryer at 90 ° C. for 48 hours or more. (B-1, average particle size = 135 μm, ε = 0.37).
For potassium chloride (hereinafter abbreviated as KCl), a special grade reagent (manufactured by Wako Pure Chemical Industries, Ltd.) was used, and the mixture was similarly classified and dried (B-2, average particle size = 200 μm, ε = 0.95). ).
As sucrose, frost sugar FS-2 (manufactured by Nissin Sugar Co., Ltd.) was used, and the sucrose was similarly classified and dried (B-3, average particle size = 41 μm, ε = 1.95).
Hydroxypropyl methylcellulose (Methcell HPMC, manufactured by Dow Chemical Co., Ltd.) was also classified and dried in the same manner (B-4, average particle size = 85 μm, ε = 1.88).

Table 3 shows D10 (particle size at the position of 10% by mass counting from the smallest particle size side) and D50 (particle size at the position of 50% by mass) of the volume distribution measured by the laser diffraction type particle size distribution diameter. , Average particle size) and D90 (particle size at the position of 90% by mass counting from the smallest particle size side) are also shown.
Furthermore, the ε value is described as a guideline for the particle size range. The smaller the value of ε, the narrower the particle size distribution.
ε = (D90-D10) ÷ D50 ・ ・ ・ ・ ・ (2)

Explanation of symbols HPMC: Hydroxypropylmethylcellulose D10: Particle size D50 at the position of 10% by mass counting from the smallest particle size side: Particle size D90 at the position of 50% by mass counting from the smallest particle size side: Smallest particle size Particle size ε at 90% by mass counting from the side: Estimated particle size distribution width, ε = (D90-D10) ÷ D50

<Synthetic Examples 6 to 12: Preparation of solvent-free polyurethane resin (A) reaction solution>
According to the formulation shown in Table 4, the high molecular weight polyol (P), the chain extender (E), the cross-linking agent (X), and the urethanization catalyst are first mixed at 80 ° C. for 1 hour, and then a mixture of polyol components (hereinafter referred to as polyol mix). ) Was prepared.

Next, the polyol mix and the polyfunctional isocyanate compound (I) were each adjusted to 60 ° C. and mixed at the blending ratios shown in Table 4 to prepare a polyurethane reaction solution.
For mixing, a rotation / revolution type mixer (manufactured by Shinky Co., Ltd., ARE-310 type, stirring condition: 2000 rpm × 120 seconds, defoaming condition: 2200 rpm × 60 seconds) was used.

Explanation of symbols in the table PCD-500: Ethanol distilled by reacting a mixture of 3-methyl-1,5-pentanediol and 1,6-hexamethylenediol (molecular ratio = 9: 1) with diethyl carbonate. Polycarbonate-based polyol (high molecular weight polyol, manufactured by Tosoh, molecular weight = 500, number of functional groups = 2.0) obtained by removing
PCD-1000: Obtained by reacting a mixture of 3-methyl-1,5-pentanediol and 1,6-hexamethylenediol (molecular ratio = 5: 5) with diethyl carbonate to remove distilled ethanol. Polycarbonate-based polyol (high molecular weight polyol, manufactured by Tosoh, molecular weight = 1000, number of functional groups = 2.0)
1,4-BD: 1,4-Butanediol (chain extender, manufactured by Mitsubishi Chemical Corporation, molecular weight = 90.1, number of functional groups = 2.0)
TMP: Trimethylolpropane (crosslinking agent, manufactured by Mitsubishi Gas Chemical Company, molecular weight = 134.2, number of functional groups = 3.0)
Bismuth-based catalyst: Neostan U-600 (manufactured by Nitto Kasei Co., Ltd., bismuth tris (2-ethylhexanoate), Bi content 18.0 to 19.0%)
[E] / [P]: (Ratio of the number of moles of active hydrogen groups [E] of the chain extender (E) to the number of moles of active hydrogen groups [P] of the high molecular weight polyol (P))
[X] / [P]: (Ratio of the number of moles [X] of active hydrogen groups of the cross-linking agent (X) to the number of moles [P] of active hydrogen groups of the high molecular weight polyol (P))
Molecular weight of polyol component: Average value of molecular weight per mole of each polyol component Number of functional groups of polyol: Average value of number of functional groups per mole of each polyol component EO content: Mass% of polyethylene glycol unit in the system

<Examples 1 to 11 and Comparative Examples 1 to 7>
As a mixer for stirring and mixing, a combination of a 2 liter polypropylene beaker (manufactured by AZONE), a high flex disperser (manufactured by SMT, HG-92 special type) and a turbine blade, or a high-speed mixer (manufactured by Nippon Coke Co., Ltd., A combination of FM-10 type Henschel mixer) and blade blades was used.

Porogen (B) was charged in advance in the tank of the mixer, and the mixture was sufficiently purged with nitrogen gas to prepare for granulation. Then, at the same time as stirring was started at a predetermined rotation speed, the polyurethane reaction solution was added dropwise based on the formulation shown in Table 5. The dropping time was 3 seconds or more and 10 seconds or less from the start of stirring. After 50 seconds from the start of stirring, stirring was stopped and the granulated particles were collected.
In Examples 8, 9, 10 and 11, when the stirring of the mixer was stopped, the particles remained tacky and the particles were slightly flexible. Therefore, 50% of the pologene (B) used was used as a dusting agent. The polyurethane resin particles were additionally charged into the mixer and mixed for 20 seconds at a peripheral speed of the stirring blade = 3.0 m / s to recover the polyurethane resin particles.

The recovered granulated product was placed in a stainless steel container, covered, and cured in a hot air dryer at 90 ° C. After that, when the peak near 2270 cm-1 in the ATR-FT-IR (manufactured by JASCO Corporation) spectrum disappeared, it was judged that the urethanization reaction was completed, and the obtained particles were sieved with a predetermined opening. Classification (eg, under a 2.0 mm sieve, above a 0.7 mm sieve) was performed to obtain polyurethane resin particles.

When the porogen (B) is NaCl or KCl, the obtained polyurethane resin particles are placed in a rut and fired at 500 ° C. for 24 hours to incinerate the polyurethane resin, and the particle size distribution of the recovered porogen (B) is measured. , It was confirmed that it has properties within the scope of rights of the present invention.

If the polyurethane resin particles used as the granulated product are water-soluble cellulose derivatives, the polyurethane resin particles should be thoroughly washed with ion-exchanged water at 25 ° C. to completely elute the porogen (B). By drying this, polyurethane porous particles could be obtained.
When the porogen (B) used is other than a water-soluble cellulose derivative, the porogen (B) can be completely eluted by thoroughly washing with warm water at 90 ° C., and by drying this, the polyurethane resin (A) can be completely eluted. ) Perforated particles were obtained. The properties of the porous particles are shown in Table 5, and the appearance is shown in FIG.

Explanation of symbols in the table Average pore diameter: The average value was obtained by observation with an optical microscope.
Pore volume: Measured with a mercury porosimeter.
Condition of the inner wall surface of the mixer: The condition of the inside of the mixer after the polyurethane resin particles are manufactured. The formation state of the block mass in which the particles were aggregated was determined. ◎: None, ○: Almost none, △: Slightly present, ×: Yes.
Shape of porous particles: The shape of porous particles in which porogen is eluted from polyurethane resin particles. ◎: Spherical, ○: Slightly distorted, △: Distorted is conspicuous, ×: Indeterminate form.
Elution of aromatic amines from the porous particles: The polyurethane porous particles after elution of porogen were immersed in high-temperature water, and the presence or absence of the eluted aromatic amines was judged. Specifically, 1 g of the porous particles was placed in 100 ml of ion-exchanged water and treated in an autoclave at 121 ° C. for 8 hours. Then, the sample cooled to room temperature was placed in a 1000 ml eggplant-shaped flask, 70 ml of methanol was further added, and the sample was heated at 70 ° C. for 30 minutes. After the heating was completed, the mixture was cooled to room temperature within 2 minutes, and the aromatic amine was extracted into the organic layer with 50 ml of tert-butyl methyl ether. The aromatic amine contained in this extract was qualitative, and the amount of aromatic amine was quantified by GC-MS (gas chromatograph-mass spectrometer) and HPLC (high performance liquid chromatograph).
Particle size distribution of recovered porogen: The obtained polyurethane resin particles were placed in a rut and fired at 500 ° C. for 24 hours to incinerate the polyurethane resin and recovered porogen (B) particle size distribution.

<Examples 1 to 11>
As shown in Tables 5 and 6, the polyurethane resin particles obtained in the present invention and the polyurethane porous particles in which porogen (B) is eluted from them have a sharp pore size distribution in a wide particle size range. It is a feature. In addition, unlike general polyurethane foam, there is no eluate such as silicone or aromatic amine, so it was confirmed that it is most suitable for the life science field and food field where high safety is required.
<Comparative Examples 1 to 7>
As described in Table 7, the porous bodies obtained in Comparative Examples 1 to 6 were obtained in Examples in terms of granulation stability, particle shape, pore diameter and shape, and elution resistance. The result was lower than that of the porous body.

In Comparative Examples 1 and 2, since the diameter of the stirring blade was small with respect to the inner diameter of the granulation tank, the mixture of Porogen (B) and the polyurethane reaction solution was insufficient, so that a rice cake-like mass was formed on the inner wall surface and also. There was a big problem in granulation stability, such as the shape of the particleized part becoming distorted.
In Comparative Example 3, since the rotation speed (peripheral speed) of the stirring blade was lower than 6.0 m / s, the stirring / shearing force became insufficient and the shape of the particles became distorted.
In Comparative Example 4, the rotation speed (peripheral speed) of the stirring blade exceeded 15.0 m / s, so that the stirring / shearing force became excessive and the pulverization of porogen (B) was promoted at the time of granulation. The pore size of the polyurethane porous particles after elution of porogen became smaller.
In Comparative Example 5, since the amount of porogen charged in the granulation tank was too small, sufficient stirring and mixing could not be performed, rice cake-like lumps were formed on the inner wall surface, and the shape of the polyurethane particles was distorted. occured.

In Comparative Example 6, the amount of porogen charged into the granulation tank was too large, so that sufficient stirring and mixing could not be performed, and the shape of the polyurethane particles was distorted.
In Comparative Example 7, by using the aromatic isocyanate, the aromatic amine was eluted from the polyurethane porous particles when hydrolyzed.

Claims (6)

A method for producing polyurethane resin particles containing porogen by adding a reaction solution of solvent-free polyurethane resin (A) while stirring porogen (B) dissolved in water in a mixer having a rotary stirring blade. In
(1) Using a mixer in which the diameter (p) of the stirring blade is 60% or more of the inner diameter of the mixer,
(2) A method for producing polyurethane resin particles , which comprises adjusting the stirring speed so that the peripheral speed of the tip of the stirring blade is 6.0 m / s or more and 15.0 m / s or less. Porogen (B) is composed of polyvinyl alcohol (saccharification degree 70% or more and less than 98%), polyethylene glycol having an alkoxylated terminal, water-soluble cellulose derivative, polyacrylamide, polymethacrylamide, sodium chloride, potassium chloride, and polysaccharide. The method for producing polyurethane resin particles according to claim 1, wherein the polyurethane resin particles are selected alone or in combination of two or more. The method for producing polyurethane resin particles according to claim 1 or 2, wherein the average particle size of the porogen (B) is 5 μm or more and less than 900 μm. The method for producing polyurethane resin particles according to any one of claims 1 to 3, wherein the index ε {(D90-D10) ÷ D50} of the particle size distribution of the porogen (B) is less than 2.00. .. Polyurethane resin (A)
Polyfunctional isocyanate compound (I) containing at least one (one) selected from the group consisting of aliphatic polyisocyanates and alicyclic polyisocyanates, and
High molecular weight polyol compound (P) containing at least one selected from the group consisting of polycarbonate-based polyols and polyether-based polyols,
The method for producing polyurethane resin particles according to any one of claims 1 to 4, further comprising a reaction product of a chain extender (E) and a cross-linking agent (X). Any of claims 1 to 5, wherein the average particle size of the particles is 400 μm or more and 3 mm or less, the average pore diameter is 5 μm or more and 900 μm or less, and the pore capacity is 2.0 cm ^ 3 / g or more. The method for producing polyurethane resin particles according to item 1 .

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