JP7842582B2 - Thermoplastic polyurethane resin composition with excellent extrusion film moldability and method for producing the same - Google Patents

Description

This invention relates to a thermoplastic polyurethane resin composition exhibiting excellent extruded film moldability, comprising specific multilayer polymer particles and a thermoplastic polyurethane elastomer, and a method for producing the same.

Thermoplastic polyurethane elastomers are widely used due to their excellent mechanical, thermal, and electrical properties. Their applications are not limited to injection molding; they are also used in extrusion molding applications such as sheet and film extrusion. As a polyurethane-based resin composition that exhibits excellent affinity with thermoplastic polyurethane elastomers without substantially impairing their superior mechanical properties and flexibility, and without problems such as bleed-out or phase separation, resin compositions of thermoplastic polyurethane elastomers and multilayer polymer particles are known. Patent Document 1 discloses a flexible resin composition of thermoplastic polyurethane elastomer and an acrylic-based flexible multilayer polymer. Furthermore, Patent Document 2 discloses a thermoplastic elastomer composition containing two or more multilayer polymer particles with optimized compositions of a thermoplastic elastomer, a rubber component layer, a thermoplastic resin component layer, the number-average molecular weight (Mn) of the outermost thermoplastic resin component, and the average particle size. Thermoplastic polyurethane elastomer is described as the thermoplastic elastomer in the examples.

Japanese Patent Publication No. 2004-238590 Japanese Patent Publication No. 2005-255872

When thermoplastic polyurethane elastomer is extruded into film, the high tackiness of the film surface causes the films to stick together during international shipping in containers. Furthermore, while adding specific multilayer polymer particles to thermoplastic polyurethane improves the film's tackiness, it results in a significant increase in surface defects in the extruded film.

In view of the above circumstances, the problem that the present invention aims to solve is to provide a thermoplastic polyurethane resin composition and a method for producing the same, which yields a film with low tackiness and few surface defects.

As a result of diligent research to solve the above problems, the present inventors have completed the present invention, which encompasses the following forms.
(Section 1)
A polyurethane resin composition comprising a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B),
The multilayer polymer particles (B) are as follows (a) to (f):
(a) The multilayer polymer particle (B) consists of two or more layers, each having at least one rubber component layer (I) inside and at least one thermoplastic resin component layer (II) on the outermost surface.
(b) The rubber component layer (I) is a polymer layer formed by copolymerization of a monomer mixture (i) consisting of 50 to 99.99% by mass of an acrylic acid ester, 49.99 to 0% by mass of another monofunctional monomer copolymerizable with the acrylic acid ester, and 0.15 to 10% by mass of a polyfunctional monomer.
(h) The thermoplastic resin component layer (II) is a polymer layer formed by polymerization of a monomer mixture (ii) consisting of 40 to 100% by mass of a methacrylic acid ester and 60 to 0% by mass of another monomer copolymerizable with the methacrylic acid ester,
(ii) The number average molecular weight of the outermost polymer of the thermoplastic resin component layer (II) is 30,000 or less by GPC method,
(e) The total mass ratio of the rubber component layer (I) to the thermoplastic resin component layer (II) [(I)/(II)] is 30/70 to 90/10, and (f) the average particle diameter of the multilayer polymer particles (B) is 150 nm or less.
A polyurethane resin composition that satisfies the above conditions and in which the multilayer polymer particles (B) are dispersed in a size of 0.1 to 10 μm.
(Section 2)
The polyurethane resin composition according to item 1, wherein the mass ratio of thermoplastic polyurethane elastomer (A) to multilayer polymer particles (B) is 95/5 to 70/30.
(Section 3)
A polyurethane resin composition according to item 1 or 2, wherein the Shore A hardness measured by a method compliant with JIS K 6253 is 60 to 95.
(Section 4)
A polyurethane resin composition for extrusion molding, as described in any one of claims 1 to 3.
(Section 5)
A polyurethane resin composition for film extrusion, as described in any one of claims 1 to 3.
(Section 6)
A step to produce a resin composition (B2) comprising a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B), wherein the melt viscosity η(B2) at a shear rate of 121.6 ^sec⁻¹ at 210°C is 100 to 1200, and the absolute value of the difference between the melt viscosity η(A) of the thermoplastic polyurethane elastomer (A) at a shear rate of 121.6 ^sec⁻¹ and the melt viscosity η(B2) is less than 200 Pa·s |η(A) - η(B2)|
A step of melt-mixing the resin composition (B2) and the thermoplastic polyurethane elastomer (A),
A method for producing a polyurethane resin composition according to any one of items 1 to 5, including the method described in item 1 to 5.

The present invention provides a thermoplastic polyurethane resin composition with low tackiness and excellent film-forming properties, as well as a method for producing the same.

In this invention, by incorporating a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B) into a polyurethane resin composition, the tackiness of the polyurethane resin composition is suppressed, and by ensuring that the dispersion diameter of the multilayer polymer particle (B) domains in the polyurethane resin composition is 0.1 to 10 μm, a polyurethane resin composition with good film moldability can be obtained. The dispersion diameter of the multilayer polymer particle (B) domains can be measured using a transmission electron microscope. The polyurethane resin composition of this invention is electron-stained with ruthenium tetroxide, and the major and minor axes of the domains derived from the multilayer polymer particles (B) in the image observed using a transmission electron microscope are measured. The sum of the major and minor axes is divided by 2 to determine the domain diameter. The dispersion diameter can be determined by performing the above measurement and calculation for any 10 or more domains and calculating the average value.

The thermoplastic polyurethane elastomer (A) used in this invention is an extrudeable thermoplastic polyurethane elastomer. This thermoplastic polyurethane elastomer can be obtained by reacting a diisocyanate compound with a compound having two or more hydroxyl groups. Among these, a material having a microphase separation structure consisting of a so-called soft segment and a hard segment, composed of a long-chain polyol, diisocyanate, and a chain extender, is preferably used.

Examples of diisocyanate compounds for synthesizing the thermoplastic polyurethane elastomer (A) used in the present invention include aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate; and aromatic diisocyanates such as p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, and 4,4'-diphenylmethane diisocyanate. Among these, aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, and 2,6-tolylene diisocyanate are preferred from the viewpoint of mechanical properties.

Furthermore, compounds having two or more hydroxyl groups include polyester polyols, which are condensation reaction products of dibasic acids such as adipic acid and phthalic acid with glycols such as ethylene glycol and 1,4-butanediol; polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethylene glycol-polypropylene glycol; polycarbonate polyols, which are reaction products of carbonates such as ethylene carbonate with glycols; and other polyols such as castor oil polyols and polyols using a butadiene skeleton. The polyurethane resin composition of the present invention is more effective against polyether polyols, which have low stability against thermal oxidative degradation, because it improves extrusion processability and broadens the molding temperature range.

The number-average molecular weight of the polyol is preferably 500 to 8,000, and more preferably 1,000 to 6,000. Here, the number-average molecular weight of the polyol as used herein is the number-average molecular weight calculated based on the hydroxyl value measured in accordance with JIS K1557.

Examples of chain extenders include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, bisphenol A, and p-xylylene glycol.

Regarding the production of the thermoplastic polyurethane elastomer (A) used in this invention, in addition to the above components, catalysts, molecular weight modifiers, etc., are used as needed. Conventional known methods such as bulk polymerization and solution polymerization can be applied to the production method. For example, in bulk polymerization, there is a one-shot method in which the polyol, chain extender, and diisocyanate are polymerized simultaneously, and a prepolymer method in which the polyol and diisocyanate are reacted beforehand to synthesize a prepolymer, and then the chain extender is added and polymerized. These methods can be used to industrially produce the elastomer by batch polymerization, band casting, and reaction extrusion.

The melt viscosity m(A) of the thermoplastic polyurethane elastomer (A) used in this invention is preferably 500 to 10,000 Pa·s, more preferably 1,000 to 8,000 Pa·s, and even more preferably 1,500 to 5,000 Pa·s, when measured at 190°C. Furthermore, the value measured at 210°C is preferably 100 to 1,500 Pa·s, more preferably 200 to 1,300 Pa·s, and even more preferably 300 to 1,000 Pa·s. When the melt viscosity at 190°C and 210°C falls within the above ranges, the polyurethane resin composition of this invention exhibits good extrusion processability. In this specification, the melt viscosity can be measured using a capillary rheometer, with a capillary diameter of 1 mmΦ and a length of 40 mm, by extruding at a piston speed of 10 mm/min (shear rate of 121.6 sec), and the resulting shear stress.

The melt flow rate (hereinafter referred to as "MFR") of the thermoplastic polyurethane elastomer (A) used in this invention is preferably 0.1 to 50 g/10 min, and particularly preferably 0.5 to 40 g/10 min. When the MFR is in the range of 0.1 to 50 g/10 min, the extrusion processability is good. The MFR for thermoplastic polyurethane elastomer (A) is the value measured using a melt indexer at a temperature of 190°C and a load of 2.16 kg, in accordance with JIS K7210.

The Shore A hardness of the thermoplastic polyurethane elastomer (A) used in this invention is preferably between 70 and 98, and more preferably between 80 and 95. A Shore A hardness in the range of 70 to 98 provides good flexibility. In this specification, Shore A hardness refers to the value measured using a durometer with a Type A indenter, in accordance with JIS K6253.

The multilayer polymer particle (B) has at least one rubber component layer (I) (hereinafter sometimes simply referred to as "layer (I)") inside and at least one thermoplastic resin component layer (II) (hereinafter sometimes simply referred to as "layer (II)") on the outermost surface. The number of layers of the multilayer polymer particle (B) used in the present invention may be two or more, and may be three or four or more. Examples of layer structures include a two-layer structure of layer (I) - layer (II) from the center; a three-layer structure of layer (I) - layer (I) - layer (II), layer (I) - layer (II) - layer (II), or layer (II) - layer (I) - layer (II); and a four-layer structure such as layer (I) - layer (II) - layer (I) - layer (II). In particular, from the viewpoint of ease of handling, a two-layer structure of layer (I) - layer (II); or a three-layer structure of layer (I) - layer (I) - layer (II) or layer (II) - layer (I) - layer (II) is preferred.

The mass ratio (layer (I)/layer (II)) of the total amount of rubber component layer (I) to the total amount of thermoplastic resin component layer (II) must be 30/70 to 90/10. If the proportion of layer (I) is below this range, the flexibility of the polyurethane resin composition of the present invention may be insufficient. If the proportion of layer (I) exceeds this range, the formation of the particle structure becomes difficult, and the melt fluidity decreases, making it difficult to knead with other components and mold the polyurethane resin composition of the present invention. The mass ratio (layer (I)/layer (II)) is preferably 50/50 to 90/10, more preferably 60/40 to 80/20.

Layer (I) must consist of a copolymer comprising 50 to 99.99% by mass of acrylic acid ester monomer units, 49.99 to 0% by mass of other monofunctional monomer units, and 0.15 to 10% by mass of polyfunctional monomer units. The other monomer units may or may not be included in the copolymer constituting layer (I), but their presence is preferred. The content of acrylic acid ester monomer units is preferably 55 to 99.9% by mass, the content of other monofunctional monomer units is preferably 44.9 to 0% by mass, and the content of polyfunctional monomer units is preferably 0.16 to 2% by mass. If the amount of acrylic acid ester monomer units is less than 50% by mass, the rubber elasticity of the multilayer polymer particles (B) and the weather resistance of the resulting polyurethane resin composition will decrease. If it exceeds 99.99% by mass, the multilayer polymer particles (B) will have difficulty forming a complete layer structure, resulting in an extreme decrease in melt fluidity and making melt mixing and molding with other components such as thermoplastic polyurethane elastomer (A) difficult. Furthermore, if the amount of polyfunctional monomer units exceeds 10% by mass, the multilayer polymer particles (B) will lose their rubber elasticity and become insufficiently flexible. If it is less than 0.15% by mass, the flexibility of layer (I) will be excessive, worsening the tackiness of the polyurethane resin composition. Here, acrylic acid ester monomer units refer to structural units introduced by the polymerization of acrylic acid esters, monofunctional monomer units refer to structural units introduced by the polymerization of monofunctional monomers, and polyfunctional monomer units refer to structural units introduced by the polymerization of polyfunctional monomers.

The raw material monomers for layer (I) will be described below.
Examples of acrylic acid esters include esters of acrylic acid with saturated aliphatic alcohols (preferably C1-C18 saturated aliphatic alcohols), such as methyl acrylate (MA), ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; esters of acrylic acid with C5 or C6 alicyclic alcohols, such as cyclohexyl acrylate; esters of acrylic acid with phenols, such as phenyl acrylate; and esters of acrylic acid with aromatic alcohols, such as benzyl acrylate. One or more acrylic acid esters can be used.

A polyfunctional monomer is a monomer that has two or more carbon-carbon double bonds in its molecule. Examples of polyfunctional monomers include esters of unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and cinnamic acid with unsaturated alcohols such as allyl alcohol and methallyl alcohol; diesters of the aforementioned unsaturated monocarboxylic acids with glycols such as ethylene glycol, butanediol, and hexanediol; and esters of dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and maleic acid with the aforementioned unsaturated alcohols. Specifically, examples include allyl acrylate, methallyl acrylate, allyl methacrylate (ALMA), methallyl methacrylate, allyl cinnamate, methallyl cinnamate, diallyl maleate, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, divinylbenzene, ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, and hexanediol di(meth)acrylate. Among these, allyl methacrylate (ALMA) is preferred. One or more polyfunctional monomers can be used.

Other monofunctional monomers include esters of methacrylic acid with saturated aliphatic alcohols (preferably C1-C22 saturated aliphatic alcohols), such as methyl methacrylate (MMA), ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, myristyl methacrylate, palmityl methacrylate, stearyl methacrylate, and behenyl methacrylate; and methacrylates such as cyclohexyl methacrylate. Examples include esters of acrylic acid with C5 or C6 alicyclic alcohols; esters of methacrylic acid with phenols such as phenyl methacrylate; esters of methacrylic acid with aromatic alcohols such as benzyl methacrylate; aromatic vinyl monomers such as styrene (St), α-methylstyrene, 1-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, and halogenated styrenes; and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile. Other monofunctional monomers can be used one or more in combination.

Layer (II) must consist of a copolymer comprising 40 to 100% by mass of methacrylic acid ester monomer units and 60 to 0% by mass of other monomer units. The other monomer units may or may not be included in the copolymer constituting layer (II), but their presence is preferred. The content of methacrylic acid ester monomer units is preferably 60 to 99% by mass, more preferably 80 to 99% by mass, and the content of other monomer units is preferably 40 to 1% by mass, more preferably 20 to 1% by mass. If the content of methacrylic acid ester monomer units is less than 40% by mass, the compatibility between the multilayer polymer particles (B) and other components such as the thermoplastic polyurethane elastomer (A) will decrease, potentially leading to insufficient dispersion during melt mixing and molding. Here, methacrylic acid ester monomer units refer to structural units introduced by the polymerization of methacrylic acid ester.

The raw material monomers for layer (II) will be explained below.
Examples of methacrylate esters include methyl methacrylate (MMA), ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, myristyl methacrylate, palmityl methacrylate, stearyl methacrylate, behenyl methacrylate, octadecyl methacrylate, phenyl methacrylate, and benzyl methacrylate. Among these, methyl methacrylate (MMA) is preferred.

Other monomers include esters of acrylic acid with saturated aliphatic alcohols (preferably C1-C18 saturated aliphatic alcohols), such as methyl acrylate (MA), ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; esters of acrylic acid with C5 or C6 alicyclic alcohols, such as cyclohexyl acrylate; styrene (St), α-methylstyrene, 1- Examples include aromatic vinyl monomers such as vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, and halogenated styrenes; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; maleimide monomers such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(p-bromophenyl)maleimide, and N-(chlorophenyl)maleimide; and polyfunctional monomers exemplified in layer (I). Among these, alkyl acrylates such as methyl acrylate (MA), ethyl acrylate, and n-butyl acrylate (BA) are preferred.

In the multilayer polymer particles (B) used in this invention, the number-average molecular weight of the copolymer constituting at least the outermost layer of the particle among the layers (II) contained therein must be 30,000 or less, preferably 29,000 or less, more preferably 28,000 or less, and even more preferably 25,000 or less, based on measurement by GPC (gel permeation chromatography). If the number-average molecular weight exceeds 30,000, the flexibility of the molded product obtained by molding the multilayer polymer particles (B) will be insufficient, and the melt flowability may also decrease. While there is no strict lower limit to the number-average molecular weight, from the viewpoint of the passability of the multilayer polymer particles (B) through the production process, it is preferable that the number-average molecular weight does not fall below 1,000. From the viewpoint of achieving both flexibility and passability through the production process, it is particularly preferable to have the number-average molecular weight in the range of 3,000 to 20,000.

The average particle diameter of the multilayer polymer particles (B) used in this invention must be 150 nm or less. If the average particle diameter of the multilayer polymer particles (B) exceeds 150 nm, the flexibility becomes insufficient. Furthermore, the melt flowability may be poor. While there is no particular lower limit to the average particle diameter, from the viewpoint of easily forming the predetermined layer structure of the multilayer polymer particles (B), an average particle diameter of 30 nm or more is preferable. An average particle diameter of 80 to 120 nm is even more preferable. The average particle diameter of the multilayer polymer particles (B) can be measured by light scattering using a HORIBA LA-950V2 laser diffraction/scattering particle size distribution analyzer, after sampling the latex during the polymerization of the multilayer polymer particles. In the case of a polyurethane resin composition, it can also be measured using a transmission electron microscope.

As for the multilayer polymer particles (B), from the viewpoint of physical properties and ease of manufacture, a multilayer polymer particle (BX) with a three-layer structure consisting of a first rubber component layer (I) (rubber component layer (Ia)), a second rubber component layer (I) (rubber component layer (Ib)), and a thermoplastic resin component layer (II) from the center is preferred.

From the viewpoint of achieving both flexibility and other mechanical properties in the polyurethane resin composition of the present invention, the mass ratio ((Ia)/(Ib)) of the rubber component layer (Ia) to the rubber component layer (Ib) is preferably 5/95 to 95/5, more preferably 20/80 to 80/20.

From the viewpoint of achieving both flexibility and other mechanical properties of the polyurethane resin composition of the present invention, it is preferable that the content of acrylic acid ester monomer units in the rubber component layer (Ia) (C _AE (Ia) (mass%)) is higher than the content of acrylic acid ester monomer units in the rubber component layer (Ib) (C _AE (Ib) (mass%)) (C _AE (Ia) > C _AE (Ib)). Furthermore, it is preferable that the amount obtained by subtracting the content of acrylic acid ester monomer units in the rubber component layer (Ib) (C _AE (Ib) (mass%)) from the content of acrylic acid ester monomer units in the rubber component layer (Ia) (C _AE (Ia) (mass%)) is 3% by mass or more (3 ≤ [C _AE (Ia) - C _AE (Ib)]), and more preferably 4 to 30% by mass (4 ≤ [C _AE (Ia) - C _AE (Ib)] ≤ 30).

Multilayer polymer particles (B) can be manufactured by performing a polymerization reaction step (S1) to form a rubber component layer (I) and a polymerization reaction step (S2) to form a thermoplastic resin component layer (II) in a layering sequence.

In polymerization reaction step (S1), monomer mixture (i) corresponding to the copolymer composition of the rubber component layer (I) is copolymerized by a known method. Similarly, in polymerization reaction step (S2), monomer mixture (ii) corresponding to the copolymer composition of the thermoplastic resin component layer (II) is copolymerized by a known method. In polymerization reaction step (S2), the polymerization conditions are adjusted so that the Mn of the constituent copolymer of at least the outermost layer (II) is 30,000 or less. Furthermore, the polymerization conditions for the entire polymerization reaction are adjusted so that the mass ratio ((i)/(ii)) of the total amount of monomer mixture (i) to the total amount of monomer mixture (ii) used in the entire polymerization reaction is within the range of 30/70 to 90/10, and the average particle size of the final multilayer polymer particles (A) is 150 nm or less.

In the polymerization reaction step (S2) that forms at least the outermost thermoplastic resin component layer (II), it is preferable to use a molecular weight modifier in a proportion of 0.4 to 10% by mass relative to the monomer mixture (ii). More preferably, the amount of molecular weight modifier used is 0.4 to 5% by mass, and particularly preferably 0.6 to 2% by mass, relative to the monomer mixture (ii).
Generally, in the production of multilayer polymer particles, the amount of molecular weight modifier used in the polymerization reaction step that forms the outermost thermoplastic resin component layer is about 0 to 0.3% by mass relative to the monomer (mixture). However, our findings indicate that if the amount of molecular weight modifier used is less than 0.4% by mass, the Mn of the thermoplastic resin component constituting the outermost layer becomes high, which may result in insufficient flexibility of the polyurethane resin composition of the present invention, and the melt fluidity may decrease, making it difficult to knead with other components and mold the polyurethane resin composition of the present invention. If the amount of molecular weight modifier used is 0.4% by mass or more, the Mn of the thermoplastic resin component constituting the outermost layer remains stably below 30,000, and both flexibility and moldability of the polyurethane resin composition can be stably achieved. Furthermore, even if the amount of molecular weight modifier used exceeds 10% by mass, no further improvement in flexibility can be obtained, and only a large amount of unnecessary molecular weight modifier remains.

Examples of molecular weight modifiers include mercaptans such as n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and mercaptoethanol; terpene mixtures consisting of terpinolene, dipentene, t-terpinene, and small amounts of other cyclic terpenes; and halogenated hydrocarbons such as chloroform and carbon tetrachloride. Among these, alkyl mercaptans such as n-octyl mercaptan are preferred. One or more molecular weight modifiers can be used.

The polymerization method for the multilayer polymer particles (B) is not particularly limited, and known methods such as emulsion polymerization, suspension emulsion polymerization, solution polymerization, and combinations thereof can be employed.

Below, as an example, we will describe the preferred polymerization conditions for multilayer polymer particles (B) produced by emulsion polymerization.

The polymerization temperature is generally between 0 and 100°C.

Examples of emulsifiers include alkali metal salts of fatty acids such as sodium oleate, sodium laurate, and sodium stearate; sulfate esters of fatty alcohols such as sodium lauryl sulfate; rosinates such as potassium rosinate; and alkylaryl sulfonic acids such as dodecylbenzenesulfonic acid. One or more emulsifiers may be used.

Radical polymerization initiators are commonly used as polymerization initiators. Peroxides such as persulfates, azobisisobutyronitrile, and benzoyl peroxide can be used individually as radical polymerization initiators. Redox initiators, which combine organic hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and paramenthane hydroperoxide with reducing agents such as transition metal salts, can also be used.

The average particle size of the multilayer polymer particles (B) can be controlled to 150 nm or less by adjusting polymerization conditions such as the amount of emulsifier added.

The multilayer polymer particles (B) after polymerization can be separated and obtained from the reaction system using known methods such as acid precipitation, salting-out, spray drying, and freeze-coagulation.

The melt viscosity of the multilayer polymer particles (B) used in this invention is preferably 1,000 to 4,000 Pa·s, more preferably 1,200 to 3,500 Pa·s, and even more preferably 1,500 to 3,000 Pa·s, as measured at 190°C. Furthermore, the melt viscosity measured at 210°C is preferably 800 to 3,000 Pa·s, more preferably 900 to 2,500 Pa·s, and even more preferably 1,000 to 2,000 Pa·s. When the melt viscosity at 180°C and 200°C falls within the above ranges, the polyurethane resin composition of this invention exhibits good extrusion processability.

The melt flow rate (hereinafter referred to as "MFR") of the multilayer polymer particles (B) used in this invention is preferably 1.0 to 50 g/10 min, and particularly preferably 5.0 to 20 g/10 min. When the MFR is in the range of 1.0 to 50 g/10 min, the extrusion processability is good. The MFR for the multilayer polymer particles (B) is the value measured using a melt indexer at a temperature of 230°C and a load of 10 kg, in accordance with JIS K7210.

The Shore A hardness of the multilayer polymer particles (B) used in this invention is preferably between 60 and 95, and more preferably between 70 and 90. A Shore A hardness in the range of 60 to 95 provides good flexibility. In this specification, Shore A hardness refers to the value measured using a durometer with a Type A indenter, in accordance with JIS K6253.

The polyurethane resin composition in this invention comprises a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B). The mass ratio ((A)/(B)) of the thermoplastic polyurethane elastomer (A) to the multilayer polymer particles (B) is preferably 95/5 to 70/30, and more preferably 92.5/2.5 to 75/25, from the viewpoint of achieving both tackiness and film moldability.

The method of mixing the thermoplastic polyurethane elastomer (A) and the multilayer polymer particles (B) is not particularly limited, but a melt mixing method is preferred. In the melt mixing method, a melt mixer such as a single-screw or multi-screw mixer, an open roll mixer, a Banbury mixer, and a kneader can be used, and the melt mixing can be performed under an inert gas atmosphere such as nitrogen gas, argon gas, and helium gas, as needed.

The polyurethane resin composition of the present invention, from the viewpoint of dispersibility of multilayer polymer particles in the composition,
(1) A step of producing a resin composition (B2) comprising a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B), wherein the melt viscosity η(B2) at a shear rate of 121.6 ^sec⁻¹ at 210°C is 100 to 1200, and the absolute value of the difference between the melt viscosity η(A) of the thermoplastic polyurethane elastomer (A) at a shear rate of 121.6 ^sec⁻¹ and the melt viscosity η(B2) is less than 200 Pa·s |η(A) - η(B2)|
(2) A step of melt-mixing the resin composition (B2) and the thermoplastic polyurethane elastomer (A),
It is preferable to manufacture it by a method that includes [a specific component].

The resin composition (B2) comprises a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B), and its mass ratio ((A)/(B)) is preferably 95/5 to 50/50, more preferably 90/10 to 55/45, and even more preferably 85/15 to 60/40.

The absolute value of the melt viscosity difference, |η(A) - η(B2)|, is preferably less than 200 Pa·s, more preferably less than 180 Pa·s, and even more preferably less than 150 Pa·s. By setting the melt viscosity difference within this range, the mixing of the resin composition (B2) and the thermoplastic polyurethane elastomer (A) is improved, and the dispersibility of the multilayer polymer particles (B) in the polyurethane resin composition is improved.

In step (2), when melt-kneading the resin composition (B2) and the thermoplastic polyurethane elastomer (A), the mass ratio of the resin composition (B2) to the thermoplastic polyurethane elastomer (A) ((A)/(B2)) is preferably 5/95 to 75/25, and more preferably 10/90 to 60/40.

Furthermore, in step (1), the temperature at which the resin composition (B2) is manufactured is not particularly limited, but is preferably 130 to 240°C. Also, in step (2), the temperature at which the resin composition (B2) and the thermoplastic polyurethane elastomer (A) are melt-mixed is not particularly limited, but is preferably 130 to 240°C.

The polyurethane resin composition of the present invention may further contain a methacrylic resin in addition to the thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B). The number-average molecular weight (Mn) of the methacrylic resin, as measured by GPC, is preferably 10,000 to 100,000, more preferably 15,000 to 50,000. When a methacrylic resin with an Mn within the above range is used, the polyurethane resin composition of the present invention exhibits superior moldability. The content of the methacrylic resin is not particularly limited; however, from the viewpoint of improving the flexibility and moldability of the polyurethane resin composition of the present invention, it is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the total amount of thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B).

The methacrylic resin is a resin containing methyl methacrylate (MMA) monomer units. The methacrylic resin may be a homopolymer of MMA (polymethyl methacrylate (PMMA)) or a copolymer of multiple monomers containing MMA. A preferred methacrylic resin (CX) consists of 40 to 100% by mass (preferably 70 to 100% by mass) of MMA units and 60 to 0% by mass (preferably 30 to 0% by mass) of other monomer units copolymerizable with MMA.

Other monomers copolymerizable with MMA include other methacrylate esters. Examples of such methacrylate esters include alkyl methacrylates such as ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, and dodecyl methacrylate; cycloalkyl methacrylates such as 1-methylcyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, and tricyclo[ ^5.2.1.02,6 ]deca-8-yl methacrylate; aryl methacrylates such as phenyl methacrylate; and aralkyl methacrylates such as benzyl methacrylate. From the viewpoint of availability, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate are preferred.

Other monomers include those other than methacrylic acid esters. Examples of such other monomers include acrylic acid esters such as methyl acrylate (MA), ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, trifluoromethyl acrylate, trifluoroethyl acrylate, pentafluoroethyl acrylate, glycidyl acrylate, allyl acrylate, phenyl acrylate, toluyl acrylate, benzyl acrylate, isobornyl acrylate, and 3-dimethylaminoethyl acrylate. In particular, from the viewpoint of availability, acrylic acid esters such as methyl acrylate (MA), ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, and t-butyl acrylate are preferred, methyl acrylate (MA) and ethyl acrylate are more preferred, and methyl acrylate (MA) is especially preferred.

The polyurethane resin composition of the present invention may optionally contain other polymers in addition to the thermoplastic polyurethane elastomer (A), multilayer polymer particles (B), and methacrylic resin, as long as the effects of the present invention are not impaired. Other polymers include olefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; styrene resins such as polystyrene, styrene-maleic anhydride copolymer, high-impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; methyl methacrylate-styrene copolymer; ester resins such as polyethylene terephthalate and polybutylene terephthalate; amide resins such as nylon 6, nylon 66, and polyamide elastomers; polyphenylene sulfide, polyether ether ketone, Examples include polysulfone, polyphenylene oxide, polyimide, polyetherimide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, and other thermoplastic resins such as phenoxy resins; thermosetting resins such as phenolic resins, melamine resins, silicone resins, and epoxy resins; polyurethane; modified polyphenylene ether; silicone-modified resins; acrylic rubber, silicone rubber; styrene-based thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin rubbers such as IR, EPR, and EPDM. One or more of these polymers may be used.

The polyurethane resin composition of the present invention may contain various additives as needed. Examples of additives include antioxidants, thermal degradation inhibitors, ultraviolet absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes/pigments, light diffusers, matting agents, anti-adhesion agents, impact resistance modifiers, and phosphors. The content of these additives can be appropriately set within a range that does not impair the effects of the present invention. For example, per 100 parts by mass of the polyurethane resin composition, it is preferable that the content of antioxidants be 0.01 to 1 part by mass, ultraviolet absorbers be 0.01 to 3 parts by mass, light stabilizers be 0.01 to 3 parts by mass, lubricants be 0.01 to 3 parts by mass, dyes/pigments be 0.01 to 3 parts by mass, and anti-adhesion agents be 0.001 to 1 part by mass.

When the polyurethane resin composition of the present invention contains other polymers and/or additives, they may be added during the polymerization of the thermoplastic polyurethane elastomer (A) and/or multilayer polymer particles (B), added during the mixing of the thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B), or added after the mixing of the thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B).

The Shore A hardness of the polyurethane resin composition of the present invention is preferably 60 to 95, and more preferably 65 to 90. A Shore A hardness in the range of 60 to 95 indicates good flexibility. In this specification, Shore A hardness refers to the value measured using a durometer with a Type A indenter, in accordance with JIS K6253.

By molding the polyurethane resin composition of the present invention described above, molded articles of any shape, such as pellets, sheets, films, pipes, fibers, hollows, and boxes, can be obtained.
Examples of molding methods include extrusion molding methods such as shape extrusion molding, extruded sheet molding, T-dye lamination molding, inflation molding, and extruded coating; injection molding methods such as insert injection molding, two-color injection molding, core-back injection molding, sandwich injection molding, and injection press molding; blow molding; calendering; press molding; slush molding; hollow molding; vacuum molding; and foam molding.

One form of a molded article is a film. Generally, materials with a thickness of 5 to 200 μm are mainly classified as "films," while those thicker than 200 μm are mainly classified as "sheets." However, in this specification, films and sheets are not clearly distinguished, and both are referred to collectively as "films." For applications of "films" according to general classification, a thickness of 8 to 200 μm is preferred. For applications of "sheets" according to general classification, a thickness of 0.2 to 4.0 mm is preferred.

As a film forming method (film formation method), extrusion molding is preferred. Examples of melt extrusion methods include the T-die method and the inflation method, with the T-die method preferred from the viewpoint of thickness accuracy and productivity. The melt extrusion temperature is preferably 130 to 240°C. From the viewpoint of suppressing thermal decomposition of the thermoplastic polyurethane elastomer, it is preferable to extrude at a cylinder temperature of 220°C or lower. Furthermore, from the viewpoint of thin film formation and improved productivity, it is preferable to extrude at a molten resin temperature of 200°C or higher in the T-die section. Examples of extruders include single-screw extruders and multi-screw extruders with two or more screwdrivers.

The T-die method is a film forming method in which a molten resin composition is spread to a desired film width with a substantially uniform thickness, extruded into a film through a slit-shaped die (lip), and then cooled by contact with a cooling roll. Generally, in the T-die method, it is desirable to set the rotation speed of the cooling roll (film take-up speed) relatively high to achieve thin film thickness and improve productivity. However, in this case, depending on the composition, unevenness in film width and thickness may occur, leading to film warping or breakage. The polyurethane resin composition of the present invention exhibits excellent extrusion moldability. Therefore, even when the film take-up speed is set relatively high in film formation using the T-die method, unevenness in film width and thickness is less likely to occur, and film warping and breakage are less likely to occur. Consequently, the polyurethane resin composition of the present invention offers excellent film productivity.

Molded articles (including films) made from the polyurethane resin composition of the present invention generally exhibit excellent flexibility and are therefore suitably used as soft components in fields such as automotive interior and exterior components, home appliance components, wire insulation, medical components, general merchandise, footwear, and transport belts.

The following describes manufacturing examples, embodiments, and comparative examples according to the present invention.

[Evaluation items and evaluation methods]
The evaluation items and evaluation methods for the manufacturing examples, examples, and comparative examples are as follows.

(Average particle size of multilayer polymer particles)
The average particle size of the multilayer polymer particles was determined by dynamic light scattering using a DLS-600 light scattering photometer manufactured by Otsuka Electronics Co., Ltd., with samples taken from latex after polymerization was complete, and then analyzed by the cumulant method.

(Number-average molecular weight of the outermost layer of multilayer polymer particles)
The number-average molecular weight of the polymer components constituting the outermost layer of multilayer polymer particles was measured by GPC using a solution obtained by thoroughly stirring a sample of multilayer polymer particles in toluene at room temperature and then centrifuging it. In this invention, the value obtained was considered to be the number-average molecular weight of the polymer constituting the outermost layer.

(Melting viscosity)
The resin compositions shown in the Examples and Comparative Examples were extruded at 210°C using a capillary rheometer (Capillograph 1D, manufactured by Toyo Seiki Seisakusho Co., Ltd.) from a capillary with a diameter of 1 mmΦ and a length of 40 mm, and the values were evaluated from the shear stress generated during the process. The values were also evaluated from the shear stress generated during extrusion at a piston speed of 10 mm/min (shear rate of 121.6 sec).

(Diameter of multilayer polymer particle aggregates)
Ultrathin sections with a thickness of 70–90 nm were cut from the resin compositions shown in the Examples and Comparative Examples using a freeze microtome. These ultrathin sections were stained with an aqueous ruthenium tetroxide solution, and the dispersion diameter of domains consisting of multilayer polymer particles (B) was evaluated using a transmission electron microscope.

(Number of defects in the product)
The resin compositions shown in the Examples and Comparative Examples were extruded using a single-screw film extruder capable of forming sheets approximately 15 cm wide. The die thickness was adjusted to 0.3 mm, and the screw rotation speed was adjusted to achieve an extrusion rate of 35 kg/hr. The resulting films were then inspected for defects of 40 μm or larger using an OCS FSA-100 polymer quality inspection device, and the number of defects per 1 ^m² was defined as the number of defects.
Furthermore, the number of defects in the products was evaluated according to the following criteria.
○: Product defect count is 5000/ ^m² or less ×: Product defect count is greater than 5000/ ^m²

(Tuckiness)
A 0.15 mm thick press sheet was obtained by press-molding the resin compositions shown in the Examples and Comparative Examples at 210°C. A small piece cut from the press sheet was attached to the back surface of a 100 g weight. The remaining press sheet after the small piece was cut out was placed on a horizontal surface, and the weight with the press sheet piece attached was placed on top of it. When the weight was pulled horizontally, the magnitude of the force at which the weight began to move was measured using a spring scale, and the tack between the press sheet piece and the remaining press sheet was evaluated. In this evaluation, a tack of 70 g or less is preferable.

(raw materials)
In the following examples and comparative examples, the following thermoplastic polyurethane elastomer (A) was used.
Polyurethane-based thermoplastic elastomer (A-1):
We used "Pandex T-1190" manufactured by DIC Covestropolymer Co., Ltd. This product is an adipate ester-based polyurethane thermoplastic elastomer.
Polyurethane-based thermoplastic elastomer (A-2):
We used "Pandex T-8190" manufactured by DIC Covestropolymer Co., Ltd. This product is an ether-based polyurethane thermoplastic elastomer.

The monomer names and their abbreviations (in parentheses) used in the manufacturing examples are shown below.
Methyl methacrylate (MMA), n-butyl acrylate (BA), methyl acrylate (MA), styrene (St), allyl methacrylate (ALMA).

(Multilayer structure polymer particles (b-1))
Under a nitrogen atmosphere, 150 parts by mass of distilled water, 1.3 parts by mass of emulsifier (Kao Corporation's "Neopelex G-15"), and 1.0 part by mass of dispersant (Kao Corporation's "Poise 520") were added to a polymerizer equipped with a stirring blade, a condenser, and a dropping funnel, and heated to 80°C to dissolve uniformly. Then, at the same temperature, 0.05 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added, and a mixture consisting of 41.25 parts by mass of n-butyl acrylate (BA) as an acrylic ester monomer, 8.75 parts by mass of styrene (St) as another monofunctional monomer, 0.3 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.25 parts by mass of surfactant (ADEKA Corporation's "Adekacol CS-141E") was added dropwise from the dropping funnel over 60 minutes to form the first layer (layer (Ia)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.02 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 15.81 parts by mass of n-butyl acrylate (BA) as an acrylic ester monomer, 3.19 parts by mass of styrene (St) as another monofunctional monomer, 1.0 part by mass of methyl methacrylate (MMA) as another monofunctional monomer, 0.16 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.1 parts by mass of a surfactant ("Adekacol CS-141E") was added dropwise from a dropping funnel over 40 minutes to form the second layer (layer (Ib)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.03 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 28.5 parts by mass of methyl methacrylate (MMA) as a methacrylate monomer, 1.5 parts by mass of methyl acrylate (MA) as another monomer, 0.3 parts by mass of n-octyl mercaptan (n-OM), and 0.15 parts by mass of a surfactant ("Adekacol CS-141E") was added dropwise from a dropping funnel over 40 minutes to form the third layer (layer (II)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour. Polymerization was terminated after confirming that 99.9% or more of each monomer had been consumed by gas chromatography. The average particle size of the particles in the obtained latex, as determined by light scattering, was 100 nm.

The obtained latex was cooled at -30°C for 24 hours to induce freeze-aggregation, and the aggregate was then thawed and extracted. It was dried under reduced pressure at 50°C for 2 days to obtain powdered, three-layered multilayer polymer particles (b-1). The number-average molecular weight (Mn) of the polymer components constituting the outermost layer was 25,000. The particle structure is shown in Table 1.

(Multilayer structure polymer particles (b-2))
Under a nitrogen atmosphere, 100 parts by mass of distilled water, 0.02 parts by mass of emulsifier (Nikko Chemicals "Nikkol ECT-3NEX"), and 0.1 parts by mass of sodium carbonate were added to a polymerizer equipped with a stirring blade, a condenser, and a dropping funnel, and heated to 80°C to dissolve uniformly. Then, at the same temperature, 0.035 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added, and a mixture consisting of 2.11 parts by mass of methyl acrylate (MA) as an acrylic acid ester monomer, 32.89 parts by mass of methyl methacrylate (MMA) as another monofunctional monomer, 0.07 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.25 parts by mass of emulsifier (Nikko Chemicals "Nikkol ECT-3NEX") was added dropwise from the dropping funnel over 60 minutes to form the first layer (layer (Ia)). After the dropwise addition was complete, the reaction was continued at 80°C for another 40 minutes, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.045 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 37.0 parts by mass of n-butyl acrylate (BA) as an acrylic ester monomer, 8.0 parts by mass of styrene (St) as another monofunctional monomer, 0.9 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.12 parts by mass of an emulsifier (Nikko Chemicals "Nikkol ECT-3NEX") was added dropwise from a dropping funnel over 70 minutes to form the second layer (layer (Ib)). After the dropwise addition was complete, the reaction was continued at 80°C for another 90 minutes, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.02 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 18.80 parts by mass of methyl methacrylate (MMA) as a methacrylate monomer, 1.2 parts by mass of methyl acrylate (MA) as another monomer, and 0.04 parts by mass of n-octyl mercaptan (n-OM) was added dropwise from a dropping funnel over 30 minutes to form the third layer (layer (II)). After the dropwise addition was complete, the reaction was continued at 80°C for another 40 minutes. Polymerization was terminated after confirming that 99.9% or more of each monomer had been consumed by gas chromatography. The average particle size of the particles in the obtained latex, as determined by light scattering, was 230 nm.

The above latex was frozen and aggregated at -30°C for 24 hours, and the aggregated material was then thawed and extracted. It was dried under reduced pressure at 50°C for 2 days to obtain powdered, three-layered multilayer polymer particles (b-2). The number-average molecular weight (Mn) of the polymer components constituting the outermost layer was 31,000. The particle structure is shown in Table 1.

(Multilayer structure polymer particles (b-3))
Under a nitrogen atmosphere, 150 parts by mass of distilled water, 1.3 parts by mass of emulsifier (Kao Corporation's "Neopelex G-15"), and 1.0 part by mass of dispersant (Kao Corporation's "Poise 520") were added to a polymerization reactor equipped with a stirring blade, a condenser, and a dropping funnel, and heated to 80°C to dissolve uniformly. Then, at the same temperature, 0.07 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added, and a mixture consisting of 100 parts by mass of n-butyl acrylate (BA) as an acrylic ester monomer, 0.12 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.35 parts by mass of surfactant (ADEKA Corporation's "Adekacol CS-141E") was added dropwise from the dropping funnel over 60 minutes to form the first layer (layer (Ia)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.03 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 28.5 parts by mass of methyl methacrylate (MMA) as a methacrylate monomer, 1.5 parts by mass of methyl acrylate (MA) as another monomer, 0.3 parts by mass of n-octyl mercaptan (n-OM), and 0.15 parts by mass of a surfactant ("Adekacol CS-141E") was added dropwise from a dropping funnel over 40 minutes to form the third layer (layer (II)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour. Polymerization was terminated after confirming that 99.9% or more of each monomer had been consumed by gas chromatography. The average particle size of the particles in the obtained latex, as determined by light scattering, was 100 nm.

The obtained latex was cooled at -30°C for 24 hours to induce freeze-aggregation, and the aggregate was then thawed and extracted. It was dried under reduced pressure at 50°C for 2 days to obtain powdered, three-layered multilayer polymer particles (b-3). The number-average molecular weight (Mn) of the polymer components constituting the outermost layer was 25,000. The particle structure is shown in Table 1.

(Multilayer structure polymer particles (b-4))
Under a nitrogen atmosphere, 150 parts by mass of distilled water, 1.3 parts by mass of emulsifier (Kao Corporation's "Neopelex G-15"), and 1.0 part by mass of dispersant (Kao Corporation's "Poise 520") were added to a polymerization reactor equipped with a stirring blade, a condenser, and a dropping funnel, and heated to 80°C to dissolve uniformly. Then, at the same temperature, 0.095 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added, and a mixture consisting of 100 parts by mass of n-butyl acrylate (BA) as an acrylic ester monomer, 0.57 parts by mass of allyl methacrylate (ALMA) as a polyfunctional monomer, and 0.475 parts by mass of surfactant (ADEKA Corporation's "Adekacol CS-141E") was added dropwise from the dropping funnel over 60 minutes to form the first layer (layer (Ia)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour, and gas chromatography confirmed that more than 99% of each monomer had been consumed.

Next, 0.005 parts by mass of a 3% aqueous solution of potassium peroxodisulfate was added to the obtained copolymer latex. Then, a mixture consisting of 28.5 parts by mass of methyl methacrylate (MMA) as a methacrylate monomer, 1.5 parts by mass of methyl acrylate (MA) as another monomer, 0.3 parts by mass of n-octyl mercaptan (n-OM), and 0.15 parts by mass of a surfactant ("Adekacol CS-141E") was added dropwise from a dropping funnel over 40 minutes to form the third layer (layer (II)). After the dropwise addition was complete, the reaction was continued at 80°C for another hour. Polymerization was terminated after confirming that 99.9% or more of each monomer had been consumed by gas chromatography. The average particle size of the particles in the obtained latex, as determined by light scattering, was 100 nm.

The obtained latex was cooled at -30°C for 24 hours to induce freeze-aggregation, and the aggregate was then thawed and extracted. It was dried under reduced pressure at 50°C for 2 days to obtain powdered, three-layered multilayer polymer particles (b-4). The number-average molecular weight (Mn) of the polymer components constituting the outermost layer was 25,000. The particle structure is shown in Table 1.

(Manufacturing Examples 1-5)
Thermoplastic polyurethane elastomer (A) and multilayer polymer particles (b-1) to (b-4) obtained in Table 1 were melt-kneaded in the ratios shown in Table 2 using a φ40 mm single-screw extruder at a cylinder temperature of 210°C. The melt-kneaded mixture was then extruded to obtain pellet-shaped resin compositions (masterbatches) (B2-1) to (B2-5). The composition and extrusion conditions of the polyurethane resin compositions are shown in Table 2.

(Examples 1-3)
Thermoplastic polyurethane elastomer (A) and resin composition (B2) were dry-blended in the ratios shown in Table 3, and the resulting film was extruded uniaxially. The film extrusion conditions were a cylinder temperature of 210°C and a T-die temperature of 210°C. The composition of the polyurethane resin composition and the results of the physical property evaluation are shown in Table 3.

(Comparative Example 1)
Thermoplastic polyurethane elastomer (A-1) was extruded as a single-screw film. The film extrusion conditions were a cylinder temperature of 210°C and a T-die temperature of 210°C. The composition of the polyurethane resin composition and the results of the physical property evaluation are shown in Table 3.

(Comparative Examples 2-4)
Thermoplastic polyurethane elastomer (A) and resin composition (B2) were dry-blended in the ratios shown in Table 3, and the resulting film was extruded uniaxially. The film extrusion conditions were a cylinder temperature of 210°C and a T-die temperature of 210°C. The composition of the polyurethane resin composition and the results of the physical property evaluation are shown in Table 3.

(Comparative Example 5)
Thermoplastic polyurethane elastomer (A) and multilayer polymer particles (b-1) were dry-blended in the ratios shown in Table 3, and the resulting film was extruded uniaxially. The film extrusion conditions were a cylinder temperature of 210°C and a T-die temperature of 210°C. The composition of the polyurethane resin composition and the results of the physical property evaluation are shown in Table 3.

The present invention provides a polyurethane resin composition with low tackiness and excellent film moldability. Molded articles, films, or sheets made from this composition are suitably used for soft materials such as automotive interior and exterior components, home appliance components, wire insulation, medical components, general merchandise, footwear, and transport belts.

Claims (6)

A polyurethane resin composition comprising a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B),
The multilayer polymer particles (B) are as follows (a) to (f):
(a) The multilayer polymer particle (B) consists of two or more layers, each having at least one rubber component layer (I) inside and at least one thermoplastic resin component layer (II) on the outermost surface.
(b) The rubber component layer (I) is a polymer layer formed by copolymerization of a monomer mixture (i) consisting of 50 to 99.99 parts by mass of an acrylic acid ester, 49.99 to 0 parts by mass of another monofunctional monomer copolymerizable with the acrylic acid ester, and 0.15 to 10 parts by mass of a polyfunctional monomer.
(h) The thermoplastic resin component layer (II) is a polymer layer formed by polymerization of a monomer mixture (ii) consisting of 40 to 100% by mass of a methacrylic acid ester and 60 to 0% by mass of another monomer copolymerizable with the methacrylic acid ester,
(ii) The number average molecular weight of the outermost polymer of the thermoplastic resin component layer (II) is 30,000 or less by GPC method,
(e) The total mass ratio of the rubber component layer (I) to the thermoplastic resin component layer (II) [(I)/(II)] is 30/70 to 90/10, and (f) the average particle diameter of the multilayer polymer particles (B) is 150 nm or less.
A polyurethane resin composition that satisfies the above conditions and has a dispersion diameter of 0.1 to 10 μm for the multilayer polymer particle (B) domain in the polyurethane resin composition. The polyurethane resin composition according to claim 1, wherein the mass ratio of thermoplastic polyurethane elastomer (A) to multilayer polymer particles (B) is 95/5 to 70/30. A polyurethane resin composition according to claim 1 or 2, wherein the Shore A hardness measured by a method compliant with JIS K 6253 is 60 to 95. A polyurethane resin composition for extrusion molding, as described in any one of claims 1 to 3. A polyurethane resin composition for film extrusion, as described in any one of claims 1 to 3. A step to produce a resin composition (B2) comprising a thermoplastic polyurethane elastomer (A) and multilayer polymer particles (B), wherein the melt viscosity η(B2) at a shear rate of 121.6 ^sec⁻¹ at 210°C is 100 to 1200, and the absolute value of the difference between the melt viscosity η(A) of the thermoplastic polyurethane elastomer (A) at a shear rate of 121.6 ^sec⁻¹ and the melt viscosity η(B2) is less than 200 Pa·s |η(A) - η(B2)|
A step of melt-mixing the resin composition (B2) and the thermoplastic polyurethane elastomer (A),
A method for producing a polyurethane resin composition according to any one of claims 1 to 5, including the method described above.