JP7166199B2 - Method for producing acrylic block copolymer pellets - Google Patents

Description

The present invention relates to a method for producing non-sticking acrylic block copolymer pellets.

Acrylic block copolymers having polymer blocks composed of acrylic acid ester units and polymer blocks composed of methacrylic acid ester units are used in various applications such as adhesives, soft materials, and resin modifiers due to their properties. is being considered for use. This acrylic block copolymer is usually produced as granular pellets for use in various molding methods such as injection molding and extrusion molding. However, acrylic block copolymers usually contain a soft component and tend to stick together, which is a problem.

In order to prevent sticking, a method of adhering an anti-sticking agent such as ethylenebisstearic acid amide to the surface of the pellets may be considered. However, when ethylene bis-stearic acid amide is used as an anti-adhesion agent, there are problems such as reduction in transparency of the resulting molded article and occurrence of die build-up.

As a method for solving this problem, a method of adding a lubricant to an acrylic block copolymer has been investigated (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-253005

It has been found that the anti-sticking methods described in the above patent documents may not be sufficient to prevent sticking. SUMMARY OF THE INVENTION It is an object of the present invention to provide pellets of an acrylic block copolymer that are sufficiently non-sticking.

The present inventors have made intensive studies to achieve the above object, and as a result, have found an acrylic block obtained through a process of bringing raw material pellets into contact with a mixed liquid containing a specific acrylic emulsion and a water-soluble thickener. Copolymer pellets have been found to be sufficiently anti-sticking.

According to the present invention, the above objects are:
[1] Raw material for acrylic block copolymer (A) having at least one polymer block (a1) composed of alkyl acrylate units and at least one polymer block (a2) composed of alkyl methacrylate units A method for producing pellets (D) containing an acrylic block copolymer (A), comprising a step of contacting the pellets with the mixed liquid (I) and a step of removing the solvent of the mixed liquid (I) adhering to the pellets. The mixed liquid (I) contains an acrylic emulsion (B) containing methacrylic resin particles and an anionic surfactant and a water-soluble thickener (C), and the concentration of the methacrylic resin particles is 0.10% by mass. 2.0% by mass or less, and the concentration of the water-soluble thickener (C) is 0.0015% by mass or more and 0.015% by mass or less, the pellet (D) containing the acrylic block copolymer (A) Production method;
[2] A pellet ( D) manufacturing method;
[3] The acrylic block copolymer according to [1] or [2], wherein the methacrylic resin particles contained in the acrylic emulsion (B) are methacrylic resin particles containing 85% by mass or more of methyl methacrylate units ( A method for producing pellets (D) containing A);
[4] The method for producing pellets (D) containing the acrylic block copolymer (A) according to any one of [1] to [3], wherein the water-soluble thickener (C) is polyethylene oxide;
[5] Pellets containing the acrylic block copolymer (A) according to [4], wherein the polyethylene oxide as the water-soluble thickener (C) has a viscosity average molecular weight of 100,000 to 8,000,000. (D) manufacturing method;
[6] A method for producing pellets (D) containing the acrylic block copolymer (A) according to any one of [1] to [5], wherein the mixed solution (I) has a zeta potential of -75 mV or less;
[7] The acrylic block copolymer (A) has a structure in which a polymer block (a2) composed of an alkyl acrylate unit is bonded to both ends of a polymer block (a1) composed of an alkyl acrylate unit. Any one of [1] to [6] having at least one in the molecule, having a weight average molecular weight of 30,000 to 250,000, and having a polymer block (a2) content of 5 to 40% by mass. A method for producing a pellet (D) containing the acrylic block copolymer (A) described in ; and [8] an acrylic block copolymer produced by the production method of any one of [1] to [7] ( Pellets (D) containing A);
This is achieved by providing

According to the present invention, acrylic block copolymer pellets that are sufficiently prevented from sticking can be obtained.

The present invention will be described in detail below. In this specification, "(meth)acrylic acid ester" is a generic term for "methacrylic acid ester" and "acrylic acid ester", and "(meth)acrylic" is a combination of "methacrylic" and "acrylic". It is a generic term.

<Acrylic block copolymer (A)>
The acrylic block copolymer (A) contained in the raw material pellets used in the present invention includes at least one polymer block (a1) composed of alkyl acrylate units and at least one polymer block composed of alkyl methacrylate units. (a2).

Examples of alkyl acrylates that are structural units of the polymer block (a1) include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate and the like.

When the main chain carbon number of the alkyl group of the above acrylic acid alkyl ester is a short-chain alkyl group having 4 or less carbon atoms (for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate etc.) tend to improve the fluidity and tensile strength of the acrylic block copolymer (A). When the main chain carbon number of the alkyl group contained in the alkyl acrylate is a long-chain alkyl group having 6 or more carbon atoms (for example, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate , lauryl acrylate, tridecyl acrylate, stearyl acrylate, etc.) tend to improve the low-temperature properties of the acrylic block copolymer (A).

The acrylic acid alkyl ester unit, which is a structural unit of the polymer block (a1), may be composed of one type alone, or may be composed of two or more types. The proportion of acrylic acid alkyl ester units contained in the polymer block (a1) is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more in the polymer block (a1). Further, the polymer block (a1) may contain 100% by mass of alkyl acrylate units.

The polymer block (a1) may contain other monomer units as long as the effect of the present invention is not impaired. Other monomers constituting such units include, for example, methacrylic acid esters having no functional group, methacrylic acid esters having a functional group, and alkyl acrylate esters other than the methacrylic acid alkyl esters and methacrylic acid alkyl esters described later. Acrylic acid esters without functional groups other than those having functional groups, acrylic acid esters having functional groups, vinyl monomers having carboxyl groups, vinyl monomers having functional groups, aromatic vinyl monomers, conjugated dienes monomers, olefin-based monomers, lactone-based monomers, and the like. When these monomers are used, they are usually used in small amounts, preferably 40% by mass or less, more preferably 20% by mass, based on the total mass of the monomers used to form the polymer block (a1). % or less, more preferably 10 mass % or less.

The glass transition temperature of the polymer block (a1) is preferably -100 to 30°C, more preferably -80 to 20°C, even more preferably -70 to 15°C. When the glass transition temperature of the polymer block (a1) is within the above range, pellets containing the acrylic block copolymer (A) that are excellent in flexibility and properties as an adhesive even in a low-temperature range can be obtained. Among the above alkyl acrylates, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, acrylic n-Octyl acid is preferred.

The acrylic block copolymer (A) may contain two or more polymer blocks (a1), in which case the polymer blocks (a1) may be the same or different. good too.

Examples of methacrylic acid alkyl esters that are structural units of the polymer block (a2) include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and n-hexyl methacrylate. , cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, and isobornyl methacrylate. Among these, methyl methacrylate, ethyl methacrylate, and propyl methacrylate are preferred, and methyl methacrylate is preferred from the viewpoints of economical availability and excellent durability and weather resistance of the resulting polymer block (a2). more preferred.

The methacrylic acid alkyl ester unit, which is a structural unit of the polymer block (a2), may be composed of one type alone, or may be composed of two or more types. The proportion of methacrylic acid alkyl ester units contained in the polymer block (a2) is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more in the polymer block (a2). Further, the polymer block (a2) may contain 100% by mass of methacrylic acid alkyl ester units.

The polymer block (a2) may contain other monomer units as long as the effect of the present invention is not impaired. Such other monomers include, for example, methacrylic acid esters having no functional groups other than methacrylic acid alkyl esters such as phenyl methacrylate and benzyl methacrylate; alkoxy methacrylates such as methoxyethyl methacrylate and ethoxyethyl methacrylate; Alkyl esters, methacrylic acid esters having a functional group such as diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, etc.; Acrylic acid esters having no functional group other than acrylic acid alkyl esters such as phenyl acid and benzyl acrylate; acrylic acid alkoxyalkyl esters such as methoxyethyl acrylate and ethoxyethyl acrylate; diethylaminoethyl acrylate; Acrylic esters having functional groups such as hydroxyethyl, 2-aminoethyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate; (meth)acrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, ( Vinyl-based monomers having a carboxyl group such as meth)acrylamide; Vinyl-based monomers having a functional group such as (meth)acrylonitrile, vinyl acetate, vinyl chloride, and vinylidene chloride; styrene, α-methylstyrene, p- Aromatic vinyl monomers such as methylstyrene and m-methylstyrene; Conjugated diene monomers such as butadiene and isoprene; Olefin monomers such as ethylene, propylene, isobutene and octene; ε-caprolactone and valerolactone lactone-based monomers such as When these monomers are used, they are usually used in small amounts, preferably 40% by mass or less, more preferably 20% by mass, based on the total mass of the monomers used to form the polymer block (a2). % or less, more preferably 10 mass % or less.

The glass transition temperature of the polymer block (a2) is preferably 50 to 150°C, more preferably 70 to 140°C, even more preferably 80 to 130°C. When the glass transition temperature of the polymer block (a2) is within the above range, it is easy to process into pellets, and when stored as pellets, there is a tendency for the stickiness at high temperatures (e.g., 50°C) to be reduced. .

The acrylic block copolymer (A) may contain two or more polymer blocks (a2), in which case the polymer blocks (a2) may be the same or different. good too.

Although the weight average molecular weight of the polymer block (a2) is not particularly limited, it is preferably in the range of 1,000 to 50,000, more preferably in the range of 4,000 to 20,000. When the weight average molecular weight of the polymer block (a2) is less than 1,000, the resulting acrylic block copolymer (A) may lack cohesion. Further, when the weight average molecular weight of the polymer block (a2) is more than 50,000, the melt viscosity of the obtained acrylic block copolymer (A) is high, and the acrylic block copolymer (A) The productivity and the moldability of pellets containing the obtained acrylic block copolymer (A) may be inferior. In addition, the weight average molecular weight (Mw) in this specification means the weight average molecular weight of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

The difference in glass transition temperature between the polymer block (a2) and the polymer block (a1) in the acrylic block copolymer (A) is preferably 70°C or higher, more preferably 100°C or higher.

The acrylic block copolymer (A) has the general formula:
(a2-a1)n
(a2-a1) n-a2
a1-(a2-a1)n
(a2-a1)nZ
(a1-a2)nZ
(Wherein, n is an integer of 1 to 30, Z represents a coupling site (coupling site after the coupling agent reacts with the polymer terminal to form a chemical bond)) is preferred. The value of n is preferably 1-15, more preferably 1-8, and even more preferably 1-4.

Among these structures, a structure in which the polymer block (a2) is bonded to both ends of the polymer block (a1) is preferable.
Specifically, the following general formula:
(a2-a1) n ₁
(a2-a1) n-a2
a1-(a2-a1)n ₁
(a2-a1)n ₁ -Z
(a1-a2)n ₁ -Z
(Wherein, n is an integer of 1 to 30, n ₁ is an integer of 2 to 30, Z represents a coupling site (coupling site after the coupling agent reacts with the polymer terminal to form a chemical bond) ) is preferably represented by The value of n ₁ is preferably 2-15, more preferably 2-8, even more preferably 2-4.

Among the above structures, linear block copolymers represented by (a2-a1)n, (a2-a1)n-a2, a1-(a2-a1)n are more preferable, represented by a2-a1 and triblock copolymers represented by a2-a1-a2 are more preferred.

The content of the polymer block (a2) in the acrylic block copolymer (A) is preferably 5 to 40% by mass.
When the content of the polymer block (a2) is less than 5% by mass, the acrylic block copolymer (A) has high fluidity and is liquid, or pellets are produced from the acrylic block copolymer (A). When cutting, for example, it may not be possible to maintain the pellet shape even if it is cut with an underwater cutter or the like. If the content of the polymer block (a2) exceeds 40% by mass, there is a tendency that pellets containing the acrylic block copolymer (A) having excellent flexibility cannot be obtained.

The content of the polymer block (a2) in the acrylic block copolymer (A) is preferably 8 to 35% by mass, more preferably 15 to 31% by mass, from the viewpoint of obtaining pellets with excellent flexibility. is more preferable.

From the viewpoint of compatibility with the methacrylic resin contained in the acrylic emulsion (B) described later and processability of the resulting pellets containing the acrylic block copolymer (A), the acrylic block copolymer (A) The weight average molecular weight of is preferably 30,000 to 250,000, more preferably 40,000 to 200,000, even more preferably 50,000 to 180,000, and 60,000 Even more preferably ~160,000. If the weight average molecular weight of the acrylic block copolymer (A) is less than 30,000, the cohesive force of the acrylic block copolymer (A) will be insufficient, and the durability of the resulting molded article or adhesive product will be affected. may be inferior. In addition, problems such as bleeding of the acrylic block copolymer (A) onto the surface of the molded product or adhesive product may occur. On the other hand, if the weight average molecular weight of the acrylic block copolymer (A) exceeds 250,000, the melt viscosity may become too high, resulting in poor productivity and workability. In addition, the compatibility with the methacrylic resin contained in the acrylic emulsion (B) described later is lowered, the transparency of the resulting molded product or adhesive product is insufficient, or the physical properties of the obtained molded product or adhesive product are affected. Unevenness may occur.

The acrylic block copolymer (A) preferably has a molecular weight distribution (Mw/Mn) of 1.0 to 1.5. When the molecular weight distribution of the acrylic block copolymer (A) is within the above range, mold contamination during molding is suppressed, and when used as an adhesive, cohesion is high, and at the same time, contamination of the adherend is prevented. can be suppressed. From the above viewpoints, the molecular weight distribution is more preferably 1.0 to 1.4, even more preferably 1.0 to 1.3. In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) mean the number average molecular weight and weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) method.

The method for producing the acrylic block copolymer (A) is not particularly limited, and it can be produced by a production method according to a known method. In general, as a method for obtaining a block copolymer having a narrow molecular weight distribution, a method of living polymerization of monomers that are constituent units is employed. Examples of such a living polymerization method include a method of living polymerization using an organic rare earth metal complex as a polymerization initiator (see, for example, JP-A-11-335432), and an alkali metal compound using an organic alkali metal compound as a polymerization initiator. Or a method of living anionic polymerization in the presence of mineral acid salts such as alkaline earth metal salts (see, for example, JP-B-7-25859), in the presence of an organic aluminum compound using an organic alkali metal compound as a polymerization initiator. A method of living anion polymerization (see, for example, JP-A-6-93060), an atom transfer radical polymerization method (ATRP) (see, for example, Macromol. Chem. Phys., 2000, 201, p. be done.

Among the above production methods, the method of performing living anionic polymerization in the presence of an organoaluminum compound causes less deactivation during polymerization, resulting in less homopolymer contamination and higher transparency of the resulting block copolymer. Moreover, since the polymerization conversion rate of the monomer is high, the amount of residual monomer in the block copolymer is small, and the generation of air bubbles can be suppressed when producing pellets composed of the acrylic block copolymer (A). Furthermore, the molecular structure of the polymer block composed of the methacrylic acid alkyl ester units becomes highly syndiotactic, which has the effect of increasing the durability of the obtained pellets containing the acrylic block copolymer (A). In addition, since living anionic polymerization is possible under relatively mild temperature conditions, the environmental load (mainly the power consumed by the refrigerator for controlling the polymerization temperature) can be reduced for industrial production. There is From the above points, the acrylic block copolymer (A) is preferably produced by a method of living anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organic aluminum compound.

Examples of the living anion polymerization method in the presence of the organoaluminum compound include an organolithium compound and the following general formula (1)
^{AlR1R2R3 ( 1} )
(In Formula (1), R ¹ , R ² and R ³ are each independently an optionally substituted alkyl group, an optionally substituted cycloalkyl group, a substituted aryl group, optionally substituted aralkyl group, optionally substituted alkoxy group, optionally substituted aryloxy group or N,N-disubstituted amino group or R ¹ is any of the groups described above, and R ² and R ³ together form an arylenedioxy group which may have a substituent. Ether compounds such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4, etc.; triethylamine, N,N,N',N'-tetramethyl ethylenediamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2'-dipyridyl, etc. A method of polymerizing a (meth)acrylic acid ester by further adding a nitrogen compound can be employed.

Examples of the organic lithium compound include alkyllithium or alkyldilithium such as n-butyllithium, sec-butyllithium and tetramethylenedilithium; aryllithium or aryldilithium such as phenyllithium and xylyllithium; benzyllithium; Examples include aralkyllithium or aralkyldilithium such as dilithium produced by reaction of diisopropenylbenzene and butyllithium; lithium amides such as lithium diisopropylamide; and lithium alkoxides such as methoxylithium.

Further, as the organoaluminum compound represented by the general formula (1), isobutylbis(2,6-di-tert-butyl-4-methyl phenoxy)aluminum, isobutylbis(2,6-di-tert-butylphenoxy)aluminum, isobutyl[2,2'-methylenebis(4-methyl-6-tert-butylphenoxy)]aluminum and the like are preferred.

The acrylic block copolymer (A) is used as raw material pellets. Raw material pellets made of the acrylic block copolymer (A) are obtained by, for example, melt extruding the acrylic block copolymer (A) into strands and cutting them with an underwater cutter, a center hot cutter, a strand cutter, or the like. , can be produced by pelletizing. The form of the raw material pellets is not particularly limited as long as it can come into contact with the mixed liquid (I) containing the acrylic emulsion (B) and the water-soluble thickener (C), which will be described later. Usually, it has a substantially cylindrical or substantially spherical (elliptical) shape, and the maximum diameter of the raw material pellet of the acrylic block copolymer (A) is preferably 2 mm to 8 mm, more preferably 2 mm to 6 mm. is more preferred. The maximum diameter of the raw material pellet can be obtained by measuring the maximum cylinder height in the case of a substantially cylindrical shape and the longest side of an ellipsoid in the case of a substantially spherical shape by measuring with a commercially available length gauge.

The content of the acrylic block copolymer (A) contained in the raw material pellets is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass in the raw material pellets. It is particularly preferred to have

Furthermore, when producing the raw material pellets, in addition to the acrylic block copolymer (A), it is blended as necessary as long as the properties of the acrylic block copolymer (A) are not impaired. Additives such as a tackifying resin, a plasticizer, a softening agent, and the like, which will be described later, may also be blended, and raw material pellets may be produced from a mixture of these.

<Acrylic emulsion (B)>
The liquid mixture (I) used in the present invention contains an acrylic emulsion (B) and a water-soluble thickener (C).

The acrylic emulsion (B) contains methacrylic resin particles. The methacrylic resin to be such methacrylic resin particles preferably contains 85% by mass or more of the methyl methacrylate unit, more preferably 88% by mass or more, and further preferably 90% by mass or more. The methyl acid unit may be 100% by mass.

Since the acrylic emulsion (B) contains a methacrylic resin having a methyl methacrylate unit content within the above range, compatibility with the raw material pellets of the acrylic block copolymer (A) is improved and transparency is improved. tend to be superior to

Further, the methacrylic resin may contain monomer units other than methyl methacrylate.
Other monomers that can constitute such other monomer units include ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, methacryl Alkyl methacrylates such as 2-ethylhexyl acid, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, and isobornyl methacrylate (excluding methyl methacrylate); methyl acrylate, ethyl acrylate, acrylic propyl acid, n-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, etc. Acrylic acid alkyl esters; (meth) acrylics such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, glycidyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate (meth)acrylic acid esters other than acid alkyl esters; aromatic vinyl compounds such as styrene, α-methylstyrene and p-methylstyrene; conjugated diene compounds such as butadiene and isoprene; olefin compounds such as ethylene and propylene; acrylic acid; methacrylic acid and the like.

Among these other monomers, methacrylic acid alkyl esters (excluding methyl methacrylate), acrylic acid alkyl esters, and methacrylic acid are preferred.
The content of other monomer units is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. Also, the content of other monomer units may be 0% by mass.

When the methacrylic resin is a methyl methacrylate copolymer, the form of the copolymer is not particularly limited, and examples thereof include random copolymers, block copolymers, graft copolymers, and alternating copolymers. mentioned. Among them, methyl methacrylate random copolymers are preferred, and methyl methacrylate-methacrylic acid random copolymers are more preferred, from the viewpoints of better anti-sticking property and availability.

The stereoregularity of the methacrylic resin is not particularly limited, and isotactic, heterotactic or syndiotactic resins can be used.
The weight average molecular weight of the methacrylic resin is preferably 50,000 to 100,000. When the weight average molecular weight is in such a range, compatibility with the acrylic block copolymer (A) is good, and transparency is high when used as a molded article or a solvent-based pressure-sensitive adhesive. Further, from the viewpoint of the balance between compatibility with the acrylic block copolymer (A) and anti-sticking property, the weight average molecular weight is more preferably 60,000 to 95,000, more preferably 70,000 to 90. ,000 is more preferred.

The method for producing the methacrylic resin is not particularly limited, but examples thereof include a solution polymerization method, a suspension polymerization method, and a bulk polymerization method. Moreover, the methacrylic resin may be a mixture of two or more polymers having different compositions or polymers obtained by different production methods. Radical polymerization initiators are preferred as the initiator used during polymerization, and examples of the radical polymerization initiator include azo compounds such as azobisisobutyronitrile (AIBN) and azobisγ-dimethylvaleronitrile; Ruperoxide, peroxyneodecanoate, diisopropyl peroxydicarbonate, t-butyl cumyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, cyclohexanone peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide Peroxides such as oxides can be mentioned. The radical polymerization initiator is generally used in an amount of 0.05 to 0.5 parts by weight per 100 parts by weight of all monomers used for producing the methacrylic resin. The polymerization is usually carried out at a temperature of 50-140° C. for 2-20 hours, and a chain transfer agent can be used to control the molecular weight of the methacrylic resin. Chain transfer agents include methyl mercaptan, ethyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, t-butyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, ethyl thioglycoate, mercaptoethanol, thio- β-naphthol, thiophenol and the like. A chain transfer agent is generally used in the range of 0.005 to 0.5% by mass based on the total monomers used in the production of the methacrylic resin.

The number average particle diameter of the methacrylic resin particles contained in the acrylic emulsion (B) is preferably 0.05 μm or more and 2.0 μm or less, more preferably 0.1 μm or more and 1.0 μm or less. More preferably, it is 15 μm or more and 0.5 μm or less. When the number average particle size is within such a range, the adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer (A) is improved, and the acrylic emulsion (B) is stabilized. can be made. If the particle size is less than 0.05 μm, adhesion tends to be poor, and if the particle size is greater than 2.0 μm, precipitation tends to increase, and production of the emulsion may become difficult. The number average particle size of the methacrylic resin particles contained in the acrylic emulsion (B) is the number average particle size obtained using a laser diffraction particle size distribution analyzer.

Such methacrylic resin particles are obtained, for example, after obtaining a polymer as described above, and if necessary, pulverizing the polymer by a wet freeze pulverization method or the like, and then pulverizing the polymer so as to have a desired number average particle size. It can be produced by classifying using a sieve or the like.

The concentration of the methacrylic resin particles contained in the acrylic emulsion (B) can be appropriately set in consideration of handling properties, emulsion stability, etc., but is preferably 10 to 70% by mass.

The acrylic emulsion (B) contains an anionic surfactant. Examples of anionic surfactants contained in the acrylic emulsion (B) include alkyl sulfates, fatty acid salts, alkylbenzene sulfonates, alphasulfo fatty acid ester salts, alkyl polyoxyethylene sulfates, monoalkyl phosphates, and alginic acid. Water-soluble salt of sodium, (meth)acrylic acid ester-unsaturated carboxylic acid copolymer; styrene-maleic anhydride copolymer salt, maleated polybutadiene salt, naphthalenesulfonate, polyacrylate, etc. . Among them, the anionic surfactant is preferably a water-soluble salt of a (meth) acrylic ester-unsaturated carboxylic acid copolymer, and a (meth) acrylic ester-unsaturated carboxylic acid copolymer Water-soluble salts are more preferred.

The above anionic surfactants may be used singly or in combination of two or more.
The concentration of the anionic surfactant in the acrylic emulsion (B) is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less.

The acrylic emulsion (B) may further contain, for example, a protective colloid such as polyvinyl alcohol, modified polyvinyl alcohol; water-soluble cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose and hydroxypropyl cellulose.

The method for producing the acrylic emulsion (B) is not particularly limited, but it can be produced, for example, as follows.
A solution obtained by dissolving a methacrylic resin in an organic solvent such as toluene or xylene, water, and an anionic surfactant are placed in a stirring device, and stirred at room temperature to 85° C. by a stirrer such as a homomixer to obtain a methacrylic resin solution. An emulsified liquid dispersed in the form of particles is obtained. This emulsified liquid may be subjected, if necessary, to a treatment for making the particles of the methacrylic resin solution finer by using a high-pressure homogenizer or the like. The acrylic emulsion (B) is obtained by distilling off the organic solvent from the resulting emulsion under reduced pressure and heating conditions. Alternatively, an acrylic emulsion in which a methacrylic resin, water and an anionic surfactant are stirred at a temperature of 100° C. to 250° C. in an autoclave-type stirring device without using an organic solvent, and the methacrylic resin is dispersed in the form of particles. (B) can also be obtained. This acrylic emulsion (B) may be subjected, if necessary, to a treatment for making the methacrylic resin particles finer by using a high-pressure homogenizer or the like. The emulsification method for producing the acrylic emulsion (B) is not limited to the emulsification methods exemplified here, and chemical emulsification methods such as inversion emulsification, phase inversion temperature emulsification, D-phase emulsification, and gel emulsification, for example. You may apply other emulsification methods, such as.

<Water-soluble thickener (C)>
The liquid mixture (I) used in the present invention contains a water-soluble thickener (C).
By including the water-soluble thickener (C) in the mixed liquid (I), the surface of the raw material pellets made of the acrylic block copolymer (A) has an anti-sticking component such as methacrylic resin particles in an appropriate state. It becomes possible to adhere, and pellets having excellent anti-sticking properties are obtained.

Examples of the water-soluble thickener (C) include polyethylene oxide, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, polyacrylic acid, polyethylene glycol, polypropylene oxide and the like. Among them, polyethylene oxide is preferable from the viewpoint of improving the adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer (A).

The viscosity average molecular weight (Mv) of polyethylene oxide that serves as the water-soluble thickener (C) is preferably 100,000 to 8,000,000, more preferably 500,000 to 1,500,000. preferable. When the viscosity-average molecular weight of polyethylene oxide, which serves as a water-soluble thickener, is within the above range, the viscosity of the mixed liquid is reduced while maintaining the adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer (A). is adequately maintained. If the molecular weight is less than 100,000, the adhesion tends to decrease, and if it is more than 8,000,000, the viscosity of the mixture tends to be high, making removal of the mixture difficult. As the viscosity-average molecular weight (Mv), for example, a molecular weight obtained by measuring the flow-down time with a capillary viscometer using a dilute solution of the polymer and its solvent can be used.

The water-soluble thickener (C) used to prepare the mixed solution (I) described later may be added as it is when preparing the mixed solution (I), but the water-soluble thickener An aqueous solution of (C) may be prepared and mixed in this state with the acrylic emulsion (B) to form a mixed solution (I). The concentration of the water-soluble thickener (C) in the aqueous solution of the water-soluble thickener (C) used when mixing with the acrylic emulsion (B) can be appropriately set in consideration of handling properties, etc., but is 0.05. It is preferably ~1% by mass.

<Mixed liquid (I)>
The mixture (I) is obtained by mixing the acrylic emulsion (B) and the water-soluble thickener (C). During such mixing, the concentration of the methacrylic resin particles in the mixture (I) is 0.10% by mass or more and 2.0% by mass or less, and the concentration of the water-soluble thickener (C) is 0.0015. Mixing should be carried out so that it may become more than mass % and 0.015 mass % or less. By bringing such mixed liquid (I) into contact with the raw material pellets of the acrylic block copolymer (A), pellets having excellent anti-sticking performance can be obtained.

From the viewpoint of adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer (A), the concentration of the methacrylic resin particles in the mixed liquid (I) is 0.30% by mass or more and 1.7% by mass. The following is preferable, and 0.50% by mass or more and 1.6% by mass or less is more preferable. From the viewpoint of the viscosity of the mixed liquid (I) and the adhesion of the methacrylic resin particles, the concentration of the water-soluble thickener (C) in the mixed liquid (I) is 0.0020% by mass or more and 0.010% by mass or less. is preferable, and 0.0025% by mass or more and 0.007% by mass or less is more preferable.

The mixed liquid (I) may contain a solvent such as water and other additives in addition to the acrylic emulsion (B) and the water-soluble thickener (C).
The zeta potential of the mixture (I) used in the present invention is preferably −75 mV or less, more preferably −85 mV or less, and even more preferably −100 mV or less. When the mixed liquid (I) has a zeta potential of −75 mV or less, the adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer (A) is improved. The zeta potential of the mixture (I) is usually -150 mV or more. The zeta potential of the mixed solution (I) can be determined using a zeta potential/particle size/molecular weight measuring system "ELSZ-2000ZS".

<Method for Producing Pellets (D) Containing Acrylic Block Copolymer (A)>
The production method of the present invention includes a step of contacting the raw material pellets of the acrylic block copolymer (A) with the liquid mixture (I) containing the acrylic emulsion (B) and the water-soluble thickener (C). .

The method of bringing the raw material pellets of the acrylic block copolymer (A) into contact with the liquid mixture (I) is not particularly limited. For example, the liquid mixture (I) is sprayed onto the raw material pellets of the acrylic block copolymer (A). and a method in which raw material pellets of the acrylic block copolymer (A) are introduced into the mixed solution (I) and brought into contact with each other.

Examples of the method of spraying the mixed liquid (I) include a method of arranging the raw material pellets on a transfer device such as a conveyor and continuously spraying the mixed liquid (I) when passing through a sprayer.

As a method for bringing the raw material pellets of the acrylic block copolymer (A) into the mixed liquid (I) and bringing them into contact, for example, the mixed liquid (I) and the raw material pellets are put into a mixing vessel equipped with a stirrer. Then, mixing is performed for a predetermined time at a temperature of 0° C. to the boiling point of the solvent contained in the mixed liquid (I), and the pellets and the mixed liquid (I) are separated by a method such as filtration.

The liquid mixture (I) adheres to the surface of the pellets that have undergone the contacting step with the liquid mixture (I). The production method of the present invention includes a step of removing the solvent of the mixed solution (I) adhering to the surface of the pellet after the contacting step. The method of removing the solvent is not particularly limited, for example, by air blowing, if necessary, air blowing using heated air, etc., to remove the solvent of the mixed solution (I) adhering to the pellet surface. can be done.

Pellets (D) containing the acrylic block copolymer (A) of the present invention thus obtained are molded by various molding methods commonly used for thermoplastic resins, such as injection molding, extrusion molding, and calender molding. It can be molded into any desired shape. In addition, it can be used as a modifier for elastomer materials, resins, rubbers, asphalt, etc., a vibration damping agent, a base polymer for adhesives, and a component for resin modifiers.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited by them. Various physical properties in Examples and Comparative Examples were measured or evaluated by the following methods.
"Weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn)"
The weight average molecular weight, number average molecular weight and molecular weight distribution of the acrylic block copolymer were obtained by gel permeation chromatography (hereinafter abbreviated as GPC) in terms of polystyrene equivalent molecular weight. Details are as follows.
・ Apparatus: GPC apparatus "HLC-8020" manufactured by Tosoh Corporation
・ Separation column: "TSKgel GMHXL", "G4000HXL" and "G5000HXL" manufactured by Tosoh Corporation connected in series ・Eluent: Tetrahydrofuran ・Eluent flow rate: 1.0 ml / min ・Column temperature: 40 ° C.
・Detection method: Differential refractive index (RI)

"Composition ratio of each polymer block"
The composition ratio of each polymer block and the composition ratio of each polymer block in the acrylic block copolymer were determined by ¹ H-NMR ( ¹ H-nuclear magnetic resonance) measurement. Details are as follows.
・ Apparatus: Nuclear magnetic resonance apparatus "JNM-LA400" manufactured by JEOL Ltd.
・Heavy solvent: deuterated chloroform

"Number average particle size of methacrylic resin particles contained in acrylic emulsion"
The average particle size of the methacrylic resin particles was determined using a laser diffraction particle size distribution analyzer. Details are as follows.
・ Apparatus: Laser diffraction/scattering particle size distribution analyzer “Microtrac MT3000II” manufactured by Microtrac Bell Co., Ltd.
・Measurement solvent: water

"Zeta potential"
The zeta potential of the mixed solution (I) was determined using an electrophoretic light scattering method (laser Doppler method). Details are as follows.
・Equipment: Zeta potential/particle size/molecular weight measurement system “ELSZ-2000ZS” manufactured by Otsuka Electronics Co., Ltd.
・Measurement solvent: water ・Measurement concentration: 0.1% by mass

"Evaluation of stickiness of pellets"
1. Into a polyethylene sample bag (length 240 mm x width 170 mm x thickness 0.08 mm), 15 g of the acrylic block copolymer (A) raw material pellets and 40 g of the mixture (I) preheated to 60 ° C. were charged. The raw material pellets are immersed in the mixed solution (I) for 15 seconds while being gently shaken.
2. After immersion, a draining net is used to separate the pellets and the mixed solution (I).
3. An air gun is used to blow air onto the pellets remaining on the draining net to blow off water (moisture) adhering to the surface of the pellets.
4. When the dried pellets were transferred to a 100 ml beaker, it was evaluated whether the pellets fell loose or fell in clumps.
AA: Pellets are completely unraveled AB: Pellets are partially clumped BB: Pellets are one clump

"Precipitation evaluation of methacrylic resin particles"
40 g of the mixed solution (I) was placed in a 100 ml screw tube, vigorously shaken up and down together with the screw tube for 15 seconds, allowed to stand at room temperature for 24 hours, and then visually evaluated for any sediment at the bottom of the screw tube. .
A: No precipitation B: With precipitation

[Production Example 1] [Acrylic block copolymer (A1)]
(1) After purging the inside of a 100 L polymerization vessel with nitrogen, 46.5 kg of toluene and 1.08 kg of 1,2-dimethoxyethane were added while stirring at room temperature, followed by isobutylbis(2,6-di 1.60 kg of a toluene solution containing 808.5 mmol of t-butyl-4-methylphenoxy)aluminum was added, and 0.06 kg of a cyclohexane solution of sec-butyllithium containing 103.95 mmol of sec-butyllithium was further added.
(2) Subsequently, 1.08 kg of methyl methacrylate was added thereto. The reaction was initially colored yellow, but became colorless after being stirred at room temperature for 60 minutes.
(3) Subsequently, the internal temperature of the polymerization liquid was cooled to -30°C, 13.53 kg of n-butyl acrylate was added dropwise over 2 hours, and after the completion of dropwise addition, the mixture was stirred at -30°C for 5 minutes.
(4) Further, 1.49 kg of methyl methacrylate was added thereto, and the mixture was stirred overnight at room temperature.
(5) After 0.50 kg of methanol was added to terminate the polymerization reaction, the resulting reaction solution was poured into 495 kg of methanol to deposit a liquid precipitate. After that, the liquid precipitate was collected and dried to obtain a polymer having a methyl methacrylate unit content (content of the polymer block (a2)) of 16.3% by mass, a weight average molecular weight of 159,000 and a molecular weight distribution of 1.10. 14.8 kg of acrylic triblock copolymer (A1) was obtained.
(6) The above production example 1 was repeated 10 times to obtain about 150 kg of acrylic triblock copolymer (A).
(7) The obtained acrylic triblock copolymer (A1) was pelletized by a strand cut method using a ZSK-25 twin-screw extruder manufactured by KRUPP WERNER & PFLEIDERER.

[Production Example 2] [Acrylic block copolymer (A2)]
(1) A 3-liter three-necked flask was fitted with a three-way cock and the inside was purged with nitrogen. Then, while stirring at room temperature, 1409 g of toluene and 32.7 g of 1,2-dimethoxyethane were added, followed by isobutylbis(2, 48.6 g of a toluene solution containing 24.5 mmol of 6-di-t-butyl-4-methylphenoxy)aluminum was added, and 2.55 g of a cyclohexane solution of sec-butyllithium containing 4.35 mmol of sec-butyllithium was added. added.
(2) Subsequently, 43.5 g of methyl methacrylate was added thereto. The reaction was initially colored yellow, but became colorless after being stirred at room temperature for 60 minutes.
(3) Subsequently, the internal temperature of the polymerization liquid was cooled to -30°C, 360 g of n-butyl acrylate was added dropwise over 2 hours, and after the dropwise addition was completed, the mixture was stirred at -30°C for 5 minutes.
(4) Further, 61.5 g of methyl methacrylate was added thereto, and the mixture was stirred overnight at room temperature.
(5) After 15 g of methanol was added to terminate the polymerization reaction, the resulting reaction solution was poured into 15 kg of methanol to deposit a liquid precipitate. After that, the liquid precipitate was collected and dried to obtain a polymer having a methyl methacrylate unit content (content of the polymer block (a2)) of 22.5% by mass, a weight average molecular weight of 111,000, and a molecular weight distribution of 1.09. 450 g of an acrylic triblock copolymer (A2) was obtained.
(6) The obtained acrylic triblock copolymer (A2) was pelletized by a strand cut method using a KZW-15 compact twin-screw extruder manufactured by Technobell Co., Ltd.

[Production Example 3] [Acrylic block copolymer (A3)]
(1) A 3-liter three-necked flask was fitted with a three-way cock and the inside was purged with nitrogen. Then, while stirring at room temperature, 1302 g of toluene and 65.1 g of 1,2-dimethoxyethane were added, followed by isobutylbis(2, 120.0 g of a toluene solution containing 60.3 mmol of 6-di-t-butyl-4-methylphenoxy)aluminum was added, and 4.34 g of a cyclohexane solution of sec-butyllithium containing 7.50 mmol of sec-butyllithium was added. added.
(2) Subsequently, 69.3 g of methyl methacrylate was added thereto. The reaction was initially colored yellow, but became colorless after being stirred at room temperature for 60 minutes.
(3) Subsequently, the internal temperature of the polymerization liquid was cooled to -30°C, 315 g of n-butyl acrylate was added dropwise over 2 hours, and after the completion of dropping, the mixture was stirred at -30°C for 5 minutes.
(4) Further, 65.9 g of methyl methacrylate was added thereto, and the mixture was stirred overnight at room temperature.
(5) After 20 g of methanol was added to terminate the polymerization reaction, the resulting reaction solution was poured into 15 kg of methanol to deposit a liquid precipitate. After that, the liquid precipitate was collected and dried to obtain a polymer having a methyl methacrylate unit content (content of the polymer block (a2)) of 30.3% by mass, a weight average molecular weight of 61,000, and a molecular weight distribution of 1.09. 440 g of an acrylic triblock copolymer (A3) was obtained.
(6) The obtained acrylic triblock copolymer (A3) was pelletized by a strand cut method using a KZW-15 compact twin-screw extruder manufactured by Technobell Co., Ltd.

[Production Example 4] [Acrylic block copolymer (A4)]
(1) A 3-liter three-necked flask was fitted with a three-way cock and the inside was purged with nitrogen. Then, while stirring at room temperature, 1409 g of toluene and 32.7 g of 1,2-dimethoxyethane were added, followed by isobutylbis(2, 48.6 g of a toluene solution containing 24.5 mmol of 6-di-t-butyl-4-methylphenoxy)aluminum was added, and 1.50 g of a cyclohexane solution of sec-butyllithium containing 2.55 mmol of sec-butyllithium was added. added.
(2) Subsequently, 22.7 g of methyl methacrylate was added thereto. The reaction was initially colored yellow, but became colorless after being stirred at room temperature for 60 minutes.
(3) Subsequently, the internal temperature of the polymerization liquid was cooled to -30°C, 434 g of n-butyl acrylate was added dropwise over 2 hours, and after the completion of dropping, the mixture was stirred at -30°C for 5 minutes.
(4) Further, 29.4 g of methyl methacrylate was added thereto, and the mixture was stirred overnight at room temperature.
(5) After 15 g of methanol was added to terminate the polymerization reaction, the resulting reaction solution was poured into 15 kg of methanol to deposit a liquid precipitate. After that, the liquid precipitate was collected and dried to obtain a polymer having a methyl methacrylate unit content (content of the polymer block (a2)) of 11.0% by mass, a weight average molecular weight of 200,000, and a molecular weight distribution of 1.11. 440 g of an acrylic triblock copolymer (A4) was obtained.
(6) The obtained acrylic triblock copolymer (A4) was pelletized by a strand cut method using a KZW-15 compact twin-screw extruder manufactured by Technobell Co., Ltd.

Block structure, weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of acrylic block copolymers (A1) to (A4) obtained in Production Examples 1 to 4 above, content of polymer block (a2) are shown in Table 1.

[Production Example 5] [Acrylic emulsion (B1)]
30 g of methacrylic resin (methyl methacrylate unit content: 90% by mass, weight average molecular weight: 85,000) was dissolved in 70 g of toluene to obtain a methacrylic resin solution. The resulting solution was mixed with 73 g of an aqueous solution containing a water-soluble salt (anionic surfactant) of a (meth)acrylic acid ester-unsaturated carboxylic acid copolymer, and then emulsified with a homomixer to obtain a methacrylic resin solution. was dispersed in the form of fine particles to obtain an emulsion. After that, toluene was distilled off from the resulting emulsion to obtain an acrylic emulsion (B1) containing methacrylic resin particles. The solid content concentration (TS) of the acrylic emulsion (B1) was 36% by mass, and the number average particle diameter of the methacrylic resin particles contained in the acrylic emulsion (B1) was 0.2 μm.

[Production Example 6] [Acrylic emulsion (B2)]
30 g of methacrylic resin (methyl methacrylate unit content: 90% by mass, weight average molecular weight: 85,000) was dissolved in 70 g of toluene to obtain a methacrylic resin solution. The resulting solution was mixed with 120 g of an aqueous solution containing a water-soluble salt (anionic surfactant) of a (meth)acrylic acid ester-unsaturated carboxylic acid copolymer, and then emulsified by a homomixer to obtain a methacrylic resin solution. was dispersed in the form of fine particles to obtain an emulsion. After that, toluene was distilled off from the resulting emulsion to obtain an acrylic emulsion (B2) containing methacrylic resin particles. The TS of the acrylic emulsion (B2) was 23% by mass, and the number average particle diameter of the methacrylic resin particles contained in the acrylic emulsion (B2) was 1.5 µm.

[Production Example 7] [Acrylic emulsion (B3)]
30 g of methacrylic resin (methyl methacrylate unit content: 90% by mass, weight average molecular weight: 85,000) was dissolved in 70 g of toluene/methyl ethyl ketone mixed solvent to obtain a methacrylic resin solution. The resulting solution was mixed with 50 g of an aqueous solution of polyvinyl alcohol (nonionic surfactant), and then emulsified with a homomixer to obtain an emulsified liquid in which the methacrylic resin solution was dispersed in the form of fine particles. After that, toluene was distilled off from the resulting emulsion to obtain an acrylic emulsion (B3) containing methacrylic resin particles. The TS of the acrylic emulsion (B3) was 40% by mass, and the number average particle diameter of the methacrylic resin particles contained in the acrylic emulsion (B3) was 1.7 μm.

[Production Example 8] [Acrylic emulsion (B4)]
30 g of methacrylic resin (methyl methacrylate unit content: 90% by mass, weight average molecular weight: 85,000) was dissolved in 70 g of toluene to obtain a methacrylic resin solution. The resulting solution was mixed with 130 g of an aqueous solution of stearyltrimethylammonium chloride (cationic surfactant) and then emulsified with a homomixer to obtain an emulsion in which the methacrylic resin solution was dispersed in the form of fine particles. After that, toluene was distilled off from the resulting emulsion to obtain an acrylic emulsion (B4) containing methacrylic resin particles. The TS of the acrylic emulsion (B4) was 20% by mass, and the number average particle diameter of the methacrylic resin particles contained in the acrylic emulsion (B4) was 0.7 µm.

Table 2 shows the type of surfactant, the number average particle size of the methacrylic resin, and the solid content concentration of the acrylic emulsions (B1) to (B4) obtained in Production Examples 5 to 8 above.

In Examples and Comparative Examples, the following water-soluble thickeners were used.
· C1: water-soluble thickener (polyethylene oxide) Mv = about 100,000
・C2: Water-soluble thickener (polyethylene oxide) Mv = about 600,000
· C3: Water-soluble thickener (polyethylene oxide) Mv = about 7,000,000

[Example 1]
The concentration of the methacrylic resin particles was 0.6% by mass, and the concentration of the water-soluble A mixed solution (I-1) was prepared in which the concentration of the viscous thickener (C2) was 0.003% by mass. The addition of the water-soluble thickener was carried out with an aqueous solution adjusted to 0.1% by mass. The water-soluble thickener used was purchased from Aldrich and used as it is. Using the raw material pellets of the acrylic block copolymer (A1) and the mixed liquid (I-1) described above, the stickiness of the pellets was evaluated by the method described above. No agglutination of pellets occurred and was "AA". In addition, precipitation of methacrylic resin particles was evaluated by the method described above. No sedimentation of the methacrylic resin particles was observed, and the dispersibility was good, giving the rating of "A". The evaluation results are shown in Table 3.

[Examples 2 to 9]
Change the formulation of the mixed solution containing water, acrylic emulsion containing methacrylic resin particles and anionic surfactant, and water-soluble thickener to the formulation shown in Table 3, or change the acrylic block copolymer. Evaluation of stickiness of pellets and evaluation of sedimentation of methacrylic resin particles were carried out in the same manner as in Example 1 except that In Examples 3 and 4, when the acrylic block copolymer was changed to (A2) or (A3), the adhesion evaluation was "AA" and the sedimentation evaluation of methacrylic resin particles was "A" in both cases. In Example 7, when a low-molecular weight type water-soluble thickener was used, the stickiness evaluation was "AB". In Example 9, when the number average particle size of the methacrylic resin particles contained in the acrylic emulsion was increased, the adhesion evaluation was "AA". The evaluation results are shown in Table 3.

[Comparative Examples 1 and 2]
In the same manner as in Example 1, except that the formulation of the mixed liquid consisting of an acrylic emulsion containing water, methacrylic resin particles, and an anionic surfactant is changed to the formulation shown in Table 3, the evaluation of the stickiness of the pellets, the methacrylic resin Particle sedimentation evaluation was performed. In Comparative Examples 1 and 2, the stickiness evaluation was "BB" only with the mixed solution of only the acrylic emulsion composed of the methacrylic resin particles. The evaluation results are shown in Table 3.

[Comparative Example 3]
Water, an acrylic emulsion containing methacrylic resin particles and an anionic surfactant, and a mixed solution containing a water-soluble thickener were mixed in the same manner as in Example 1, except that the formulation was changed to that shown in Table 3. Adhesion evaluation and sedimentation evaluation of methacrylic resin particles were performed. The evaluation results are shown in Table 3.

[Comparative Example 4]
Pellets and the sedimentation evaluation of the methacrylic resin particles, the agglutination evaluation was "BB" and the sedimentation of the methacrylic resin particles was not observed and was "A". The evaluation results are shown in Table 3.

[Comparative Example 5]
Pellets in the same manner as in Example 1 except that a mixed solution obtained by mixing an acrylic emulsion containing a cationic surfactant instead of an anionic surfactant and a water-soluble thickener is used to make the formulation shown in Table 3. and the sedimentation evaluation of the methacrylic resin particles, the agglutination evaluation was "BB" and the sedimentation of the methacrylic resin particles was not observed and was "A". The evaluation results are shown in Table 3.

As shown in Examples 1 to 9 above, the acrylic block copolymer raw material pellets are brought into contact with a mixed liquid containing an acrylic emulsion containing methacrylic resin particles and an anionic surfactant, and a water-soluble thickener. The effect of suppressing agglutination was obtained in the pellets produced by the production method of the present invention, in which the solvent of the mixed solution adhering to the pellets was removed.

When the molecular weight of the water-soluble thickener is low as in Example 7, the anti-sticking performance of the pellets is somewhat inferior, so the viscosity-average molecular weight tends to be preferably 500,000 or more. Furthermore, when the number average particle size of the methacrylic resin particles is large as in Example 9, precipitation of the methacrylic resin particles was observed, so the storage stability was poor, but the anti-sticking performance was excellent.

In addition, in the case of acrylic emulsions composed of methacrylic resin particles containing nonionic or cationic surfactants as in Comparative Examples 4 and 5, the anti-sticking performance of pellets is inferior, so it is necessary to use anionic surfactants. be.

On the other hand, in the formulations outside the scope of the present invention as in Comparative Examples 1 to 3, the effect of suppressing pellet sticking was not obtained. Further, when the zeta potential of the methacrylic resin particles in the mixed liquid is -75 mV or less, the adhesion of the methacrylic resin particles to the raw material pellets of the acrylic block copolymer tends to be improved.

Claims (7)

Raw material pellets of an acrylic block copolymer (A) having at least one polymer block (a1) composed of alkyl acrylate units and at least one polymer block (a2) composed of alkyl methacrylate units, A method for producing pellets (D) containing an acrylic block copolymer (A), comprising a step of contacting the mixed solution (I) and a step of removing the solvent of the mixed solution (I) adhering to the pellets, ,
Mixture (I) contains acrylic emulsion (B) containing methacrylic resin particles and an anionic surfactant and water-soluble thickener (C), and the concentration of methacrylic resin particles is 0.10% by mass or more and 2.0 % by mass or less, the concentration of the water-soluble thickener (C) is 0.0015% by mass or more and 0.015% by mass or less,
A method for producing pellets (D) containing an acrylic block copolymer (A). 2. Pellets (D) containing the acrylic block copolymer (A) according to claim 1, wherein the methacrylic resin particles contained in the acrylic emulsion (B) have a number average particle size of 0.05 μm or more and 2.0 μm or less. Production method. 3. Pellets containing the acrylic block copolymer (A) according to claim 1 or 2, wherein the methacrylic resin particles contained in the acrylic emulsion (B) are methacrylic resin particles containing 85% by mass or more of methyl methacrylate units. (D) manufacturing method. The method for producing pellets (D) containing the acrylic block copolymer (A) according to any one of claims 1 to 3, wherein the water-soluble thickener (C) is polyethylene oxide. Pellets (D) containing the acrylic block copolymer (A) according to claim 4, wherein the polyethylene oxide as the water-soluble thickener (C) has a viscosity average molecular weight of 100,000 to 8,000,000. manufacturing method. The method for producing pellets (D) containing the acrylic block copolymer (A) according to any one of claims 1 to 5, wherein the zeta potential of the methacrylic resin particles in the mixture (I) is -75 mV or less. . In the acrylic block copolymer (A), a structure in which polymer blocks (a2) each composed of an alkyl acrylate unit are bonded to both ends of a polymer block (a1) composed of an alkyl acrylate unit is formed in the molecule. 7. The acrylic according to any one of claims 1 to 6, which has at least one, has a weight average molecular weight of 30,000 to 250,000, and has a content of the polymer block (a2) of 5 to 40% by mass. A method for producing a pellet (D) containing a block copolymer (A).