JP2023117838A - Powder composition comprising acrylic polymer, polymer composition, hot-melt adhesive, and method for producing them - Google Patents

Abstract

To provide a powder composition comprising an acrylic polymer suitable for a hot-melt adhesive, which is less malodorous as compared to the conventional ones, has reduced environmental load, and also has transparency and a good appearance.SOLUTION: Provided is a powder composition comprising an acrylic polymer, for use in a polymer composition applicable to a hot-melt adhesive, wherein the powder composition comprises a copolymer comprising a methacrylic monomer-derived constitutional unit and an alkaline compound, and wherein secondary particles thereof have a volume average particle size of 20-80 μm.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to powder compositions, polymer compositions, hot-melt adhesives, and methods for producing them, which contain acrylic polymers.

A hot-melt adhesive is an adhesive that is solid or semi-solid at room temperature and that melts and becomes fluid when heated. In particular, reactive hot-melt adhesives mainly composed of urethane prepolymers having isocyanate groups at their ends are called reactive hot-melt adhesives, and most of them are moisture-curing urethane adhesives. It is also in the form of a urethane prepolymer having isocyanate groups.

These reactive hot melt adhesives are applied to the substrate in a heated and melted state, and after cooling and solidifying, moisture curing occurs due to a chemical cross-linking reaction between the isocyanate group and water, resulting in tough, heat-resistant and chemical-resistant adhesives. Forms a film (adhesive layer) with

Conventional reactive hot melt adhesives exhibit excellent adhesiveness when chemical crosslinks are formed by moisture curing, but have the problem that chemical crosslinks hardly occur immediately after application. In addition, the temperature of the adhesive is high immediately after heating and melting, and the thermoplastic polymer has fluidity, so there is a problem that the initial adhesive strength to the substrate is not sufficient. The initial adhesive strength means the adhesive strength before moisture curing after application to the base material. Furthermore, conventional reactive hot-melt adhesives have the problem that the adhesive turns yellow immediately after being heated and melted, deteriorating its appearance.
As a means for increasing the initial adhesive strength, a method of adding a thermoplastic resin to a hot-melt adhesive to improve the initial adhesive strength is known.
Patent Document 1 discloses an acrylic resin powder for a reactive hot-melt adhesive that is easily dissolved in polyalkylene glycol.

In recent years, VOC components, which are volatile organic solvents generated from chemical substances such as adhesives used in automobile interiors, have become a problem, and regulations are becoming stricter in various countries. Acrylic resins for reactive hot-melt adhesives are also desired to be developed that contain as little low-molecular-weight VOC components as possible. However, when the acrylic resin powder composition described in Patent Document 1 is dissolved in polypropylene glycol, which is the main component of the hot melt, and heated, there is a problem that a peculiar odor is generated.

WO2018/012234

The present invention has been made to solve such problems. That is, an object of the present invention is to provide a powder composition containing an acrylic polymer suitable for hot-melt adhesives, which is less odorous than conventional products, has a low environmental load, is transparent and has a good appearance. That's what it is.

The gist of the present invention is the following [1] to [18].
[1] A powder composition containing an acrylic polymer containing a copolymer having a structural unit derived from a (meth)acrylic monomer and an alkaline compound, and having secondary particles with a volume average particle size of 20 to 80 μm. thing.
[2] The powder composition according to [1], wherein the primary particles have a volume average particle size of 0.1 to 10 μm.
[3] The powder composition according to [1] or [2], which has a mass average molecular weight of 10,000 to 500,000.
[4] The powder composition is soluble when the powder composition is mixed with polypropylene glycol having a number average molecular weight of 1000 to a concentration of 10% by mass and stirred at 60 ° C. for 60 minutes. , the powder composition according to any one of [1] to [3].
[5] The powder composition according to any one of [1] to [4], wherein the alkaline compound is an alkali metal or alkaline earth metal hydroxide.
[6] The powder composition according to any one of [1] to [5], wherein the content of the alkaline compound is 0.005 parts by mass or more relative to 100 parts by mass of the copolymer.
[7] A polymer composition comprising the powder composition according to any one of [1] to [6] and polyalkylene glycol.
[8] The polymer composition according to [7], wherein the polyalkylene glycol has a number average molecular weight of 200 to 5,000.
[9] The polymer composition according to [7] or [8], which has an odor evaluation value of 100,000,000 or less as measured by the following odor evaluation method.
(Odor evaluation method)
Powder composition containing acrylic polymer/polypropylene glycol (number average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 20/80 (mass%), on a water bath at 80 ° C. Stir for 60 minutes to dissolve the powder composition in the polypropylene glycol. The stirring is carried out at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm and a total height of 95 mm.
0.1 g of the resulting solution is weighed into a 20-mL vial, sealed, heated at 140° C. for 2 hours, and the generated gas is measured by headspace GC/MS. Thereafter, ion extraction is performed at m/z=87, and the odor evaluation value is obtained by dividing the peak area with a retention time of 2.8 to 3.2 minutes by the sample amount (g) and volume of 20 mL. The analysis conditions for headspace GC/MS are as follows.
<Analysis conditions>
Measuring machine: GC/MS 7890B/5977A manufactured by Agilent Technology
Column: UA-5 manufactured by Frontier Lab (30 m × 0.25 mm I.D. film thickness 0.25 μm)
Column temperature: 40 ° C. (held for 5 min) → 10 ° C./min temperature increase → 300 ° C. (held for 5 min)
Carrier gas: He (flow rate: 1.0 mL/min)
Inlet mode: split (split ratio 100:1)
Inlet temperature: 280°C
Transfer line temperature: 280°C
Injection volume: 250 μL
[10] The polymer composition according to any one of [7] to [9], further comprising a polyester polyol.
[11] The polymer composition according to any one of [7] to [10], further comprising an isocyanate.
[12] A hot-melt adhesive containing the polymer composition according to any one of [7] to [11].
[13] A method for producing a powder composition containing an acrylic polymer, comprising the following steps I to III.
[Step I]
(a) in a medium containing water as a main component, in the presence of an emulsifier having a critical micelle concentration or less and a water-soluble radical polymerization initiator, having a solubility of 0.02% by mass or more in the medium at 20°C; and polymerizing the monomer mixture (a), the polymer of which is insoluble in the medium, to obtain a polymer dispersion (A). Then, (b) a monomer mixture (b) containing methyl methacrylate for the polymer dispersion (A), and 0.1 to 0.1 parts per 100 parts by mass of the monomer mixture (b) 3 parts by mass of a chain transfer agent is dropped and polymerized to obtain a polymer dispersion (B). However, the total amount of the water-soluble radical polymerization initiator used in (a) and (b) is based on the total amount of 100 parts by mass of the monomer mixture (a) and the monomer mixture (b) It is 0.1 parts by mass or more.
[Step II]
An alkaline compound is added to the polymer dispersion (B) to obtain a polymer dispersion (B').
[Step III]
A powder composition is obtained from the polymer dispersion (B′).
[14] The method for producing a powder composition according to [13], wherein the polymer dispersion (B') has a pH of 4.0 or higher.
[15] The method for producing a powder composition according to [13] or [14], wherein the water-soluble radical polymerization initiator is a persulfate.
[16] A method for producing a polymer composition, comprising dissolving the powder composition obtained by the production method according to any one of [13] to [15] in polyalkylene glycol.
[17] A step of dissolving the powder composition obtained by the production method according to any one of [13] to [15] in polyalkylene glycol to obtain a polymer composition; and obtaining a prepolymer.
[18] The method for producing a polymer composition according to [17], wherein the polymer composition is a hot-melt adhesive.

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a powder composition containing an acrylic polymer suitable for hot-melt adhesives, which has less odor than conventional products, has a low environmental load, is transparent and has a good appearance. can.

The present invention will be described in detail below.
In addition, unless otherwise specified, the numerical range represented by using "~" in this specification means a range including the numerical values described before and after "~" as lower and upper limits, and "A ~ B" means greater than or equal to A and less than or equal to B.
"(Meth)acryl" is a generic term for acryl and methacryl.

<<Powder composition containing acrylic polymer>>
The powder composition containing the acrylic polymer of the present invention is a copolymer having a structural unit derived from a (meth)acrylic monomer (hereinafter also simply referred to as "copolymer (X)") and an alkaline It contains a compound, and the secondary particles have a volume average particle diameter of 20 to 80 μm.

(Copolymer (X))
The acrylic polymer contained in the powder composition of the present invention is copolymer (X), ie, a copolymer having structural units derived from (meth)acrylic monomers. Methyl methacrylate is preferable as the (meth)acrylic monomer. By having a structural unit derived from methyl methacrylate, the initial adhesive strength of the hot-melt adhesive is improved.
The mass ratio of the structural units derived from methyl methacrylate to all the structural units of the copolymer (X) is preferably 20 to 80% by mass because the initial adhesive strength of the hot-melt adhesive is improved.

The copolymer (X) may have structural units derived from other monomers copolymerizable with methyl methacrylate in addition to the structural units derived from methyl methacrylate.
Examples of the other monomers include (meth)acrylic acid alkyl esters, (meth)acrylic acid cycloalkyl esters, hydroxyl group-containing (meth)acrylic acid esters, carboxyl group-containing monomers, and carbonyl group-containing Examples include (meth)acrylic acid esters, (meth)acrylic acid esters having an amino group, styrene, and derivatives thereof.

Examples of (meth)acrylic acid alkyl esters include methyl acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, and 2-(meth)acrylate. Examples include ethylhexyl and octyl (meth)acrylate.
Examples of cycloalkyl (meth)acrylates include cyclohexyl (meth)acrylate and isobornyl (meth)acrylate.
Examples of (meth)acrylic acid esters having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.
Examples of monomers having a carboxyl group include (meth)acrylic acid, 2-(meth)acryloylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl Tetrahydrophthalic acid, 2-(meth)acryloyloxypropyltetrahydrophthalic acid, 5-methyl-2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyl Oxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, 2 -(Meth)acryloyloxyethyl oxalate, 2-(meth)acryloyloxypropyl oxalate, crotonic acid, fumaric acid, maleic acid, itaconic acid, and sorbic acid.
Examples of (meth)acrylic acid esters having a carbonyl group include 2-acetoacetoxyethyl (meth)acrylate.
Examples of (meth)acrylic acid esters having an epoxy group include glycidyl (meth)acrylate.
Examples of (meth)acrylic acid esters having an amino group include 2-dimethylaminoethyl (meth)acrylate and 2-diethylaminoethyl (meth)acrylate.
These may be used individually by 1 type, and may use 2 or more types together.

In terms of good compatibility with polyalkylene glycol, the copolymer (X) has a structure derived from methacrylic acid C4-C8 alkyl ester, which is an ester of an aliphatic alcohol having 4 to 8 carbon atoms and methacrylic acid. It is preferred to have units. Examples of the C4-C8 alkyl methacrylate include n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and octyl methacrylate. Among them, it is industrially advantageous to use n-butyl methacrylate, i-butyl methacrylate, and t-butyl methacrylate for the copolymer (X) because they are inexpensive and readily available.

In terms of good moisture resistance of the resulting hot-melt adhesive, hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate are added. It is preferable to use the (meth)acrylic acid ester having in the copolymer (X).

The copolymer (X ) preferably has a structural unit derived from a monomer having a carboxyl group. In addition, it is more preferable to have a structural unit derived from methacrylic acid, since copolymerization with methyl methacrylate units and C4-C8 alkyl methacrylic acid ester units is good.

The mass ratio of the structural units derived from methyl methacrylate to the total structural units of the copolymer (X) is preferably 20 to 80% by mass, more preferably 25 to 75% by mass, even more preferably 30 to 75% by mass.
The mass ratio of structural units derived from other monomers to all structural units of the copolymer (X) is preferably 20 to 80% by mass, more preferably 25 to 75% by mass, and even more preferably 25 to 70% by mass. . By setting the mass ratio of structural units derived from other monomers within the above range, both the solubility in polyalkylene glycol and the initial adhesive strength of the hot-melt adhesive can be achieved.

Since the compatibility with polyalkylene glycol is good, the structural unit derived from the methacrylic acid C4-C8 alkyl ester with respect to the total structural units of the copolymer (X) is preferably 20 to 80% by mass, and 25 to 75 mass. %, more preferably 25 to 70% by mass.
From the viewpoint of good storage stability of the hot-melt adhesive, the mass ratio of the (meth)acrylic acid ester-derived structural unit having a hydroxyl group to the total structural units of the copolymer (X) should be 20% by mass or less. Preferably, 10% by mass or less is more preferable.
The mass ratio of the structural units derived from methacrylic acid to the total structural units of the copolymer (X) is preferably 0.1 to 5% by mass, from the viewpoint that the initial adhesive strength of the hot melt adhesive can be further increased. .3 to 3% by mass is more preferred.

(alkaline compound)
Examples of alkaline compounds include inorganic alkaline agents and organic alkaline agents.
Examples of inorganic alkali agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal silicates such as sodium orthosilicate, sodium metasilicate and sodium sesquisilicate; and alkalis such as trisodium phosphate. Examples include metal phosphates, alkali metal carbonates such as disodium carbonate, sodium hydrogencarbonate and dipotassium carbonate, and alkali metal borates such as sodium borate. Alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide can also be used.

Examples of organic alkaline agents include hydroxyalkylamines and quaternary ammonium salts. Hydroxyalkylamines include, for example, monoethanolamine, diethanolamine, triethanolamine, methylethanolamine, methyldiethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, methylpropanolamine, methyldipropanolamine, and aminoethylethanol. Amines can be exemplified. Examples of quaternary ammonium salts include tetramethylammonium hydroxide and choline.
These may be used individually by 1 type, and may use 2 or more types together.

As the alkaline compound, an inorganic alkaline agent is preferable because it is easily available and inexpensive, and an alkali metal hydroxide or an alkaline earth metal hydroxide is preferable, and an alkali metal hydroxide is preferable from the viewpoint of water solubility. is more preferred, and one or more of sodium hydroxide and potassium hydroxide are particularly preferred.

The content of the alkaline compound in the powder composition of the present invention is preferably 0.005 parts by mass or more, more preferably 0.05 to 5 parts by mass, with respect to 100 parts by mass of the copolymer (X). 0.05 to 4 parts by weight is more preferred, and 0.05 to 3 parts by weight is particularly preferred. When the content of the alkaline compound is at least the above lower limit, the decomposition products of the polyalkylene glycol during heating are easily suppressed, and the odor of the hot-melt adhesive is reduced. If the content of the alkaline compound is equal to or less than the upper limit, the hot melt adhesive will have good storage stability.

(Volume average particle size of primary particles)
The volume average particle size of the primary particles of the powder composition of the present invention is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, even more preferably 0.2 to 2 μm. The term “primary particles” as used herein refers to the smallest unit of polymer particles that constitute a powder composition containing an acrylic polymer. When the volume average particle diameter of the primary particles is equal to or less than the upper limit, the surface area of the particles is increased, and the solubility in media such as polyalkylene glycol is improved. In addition, if the volume average particle size of the primary particles is at least the lower limit, heat fusion of the volume average particle size of the secondary particles when powdered is suppressed, and dispersibility in media such as polyalkylene glycol is improved. becomes good.

(Volume average particle diameter of secondary particles)
The secondary particles of the powder composition of the present invention have a volume average particle size of 20 to 80 μm, preferably 20 to 60 μm, more preferably 30 to 50 μm. "Secondary particles" as used herein refers to aggregated particles in which a large number of primary particles are aggregated. When the volume average particle size of the secondary particles is at least the lower limit, dusting is suppressed, and handling is facilitated. Further, when the volume average particle size of the secondary particles is equal to or less than the upper limit, the solubility in polyalkylene glycol is improved.
In the case of such an aggregated structure, it is preferable that the primary particles are loosely aggregated without being strongly bonded to each other. Specifically, the volume average particle size after irradiation with ultrasonic waves in an aqueous medium is preferably 0.2 to 20 μm. Dispersion also precedes dissolution, resulting in higher surface area and faster dissolution.

(mass average molecular weight)
The mass average molecular weight of the powder composition containing the acrylic polymer of the present invention determined by GPC (gel permeation chromatography) is preferably 10,000 to 500,000, more preferably 20,000 to 200,000. 30,000 to 150,000 is more preferable, and 30,000 to 100,000 is particularly preferable. When the mass average molecular weight is at least the lower limit, the initial adhesive strength of the adhesive tends to be good. If the weight average molecular weight is equal to or less than the upper limit, the viscosity of the polymer composition and hot-melt adhesive can be suppressed.

The powder composition containing the acrylic polymer of the present invention was obtained by mixing the powder composition with polypropylene glycol having a number average molecular weight of 1000 so as to have a concentration of 10% by mass, and stirring at 60 ° C. for 60 minutes. preferably soluble in If the powder composition is soluble, the powder composition has good coatability when used as a polymer composition or a hot-melt adhesive, making it easier to form a uniform coating film.
Here, "stirring" means, for example, when using a total of 100 g of a powder composition containing polypropylene glycol and an acrylic polymer, a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm, and a total height of 95 mm. means stirring at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm.

"It is soluble when it is mixed with polypropylene glycol having a number average molecular weight of 1000 at a concentration of 10% by mass and stirred at 60 ° C. for 60 minutes." It means judged to be soluble in both.

Judgment method A:
Powder composition / polypropylene glycol (number average molecular weight 1000) = 10/90 (mass%), the powder composition was stirred at 60 ° C. for 60 minutes to dissolve the powder composition in polypropylene glycol, and the resulting polymer composition The material is diluted 5-fold with polypropylene glycol (number average molecular weight 1000) and subjected to suction filtration on a nylon mesh gauze (300 mesh). A powder composition containing an acrylic polymer is determined to be soluble in polypropylene glycol when the filtration residue is 1% by mass or less relative to the polymer composition.

Judgment method B:
Powder composition / polypropylene glycol (number average molecular weight 1000) = 10/90 (mass%), the powder composition was stirred on a water bath at 60 ° C. for 60 minutes to dissolve the powder composition in polypropylene glycol. The polymer composition is diluted 5-fold with polypropylene glycol (number average molecular weight: 1000), and the degree of dispersion is measured by the measurement method described in JIS K5600-2-5. When the measured degree of dispersion is 20 μm or less, it is determined that the powder composition containing the acrylic polymer is soluble in polypropylene glycol.

The powder composition containing the acrylic polymer of the present invention may contain unreacted monomers used in the production of the copolymer (X). From the viewpoint of reducing the content of, it is preferably as small as possible.
The content of unreacted monomers in the powder composition containing the acrylic polymer of the present invention is preferably 1000 mass ppm or less, more preferably 500 mass ppm or less.

The powder composition containing the acrylic polymer of the present invention may contain additives such as antifoaming agents, if necessary.

(Method for producing powder composition containing acrylic polymer)
As a method for producing a powder composition containing the acrylic polymer of the present invention, a method including the following steps I to III can be exemplified.
Step I: (a) In a medium containing water as a main component, in the presence of an emulsifier having a critical micelle concentration or less and a water-soluble radical polymerization initiator, a solubility of 0.02% by mass or more in the medium at 20°C. and the polymer is insoluble in the medium, is polymerized to obtain a polymer dispersion (A). Then, (b) a monomer mixture (b) containing methyl methacrylate for the polymer dispersion (A), and 0.1 to 0.1 parts per 100 parts by mass of the monomer mixture (b) 3 parts by mass of a chain transfer agent is dropped and polymerized to obtain a polymer dispersion (B). However, the total amount of the water-soluble radical polymerization initiator used in (a) and (b) is based on the total amount of 100 parts by mass of the monomer mixture (a) and the monomer mixture (b) It is 0.1 parts by mass or more.
Step II: Add an alkaline compound to the polymer dispersion (B) to obtain a polymer dispersion (B').
Step III: A powder composition is obtained from the polymer dispersion (B').

(Step I (b))
In step I(a), the monomer mixture (a) is polymerized in a medium containing water as a main component in the presence of an emulsifier having a critical micelle concentration or less and a water-soluble radical polymerization initiator. Thereby, seed particles having a relatively large particle size can be prepared. By preparing seed particles having a relatively large particle size, generation of new particles in the subsequent step I (b) can be suppressed, and the resulting polymer has a relatively large particle size. As a result, the powder composition obtained in step II has good dispersibility in media such as polyalkylene glycol.

A "medium containing water as a main component" means a medium containing tap water, pure water, ultrapure water, distilled water, or ion-exchanged water as a main component. These may be used individually by 1 type, and may use 2 or more types together.

Examples of emulsifiers include anionic surfactants and nonionic surfactants.
Examples of anionic surfactants include alkylbenzene sulfonates, alkyl sulfonates, alkyl sulfates, fatty acid metal salts, polyoxyalkyl ether sulfates, polyoxyethylene carboxylate sulfates, polyoxyethylene Alkylphenyl ether sulfate, dialkyl succinate sulfonate (for example, sodium dioctyl sulfosuccinate, etc.), polyoxyethylene alkyl (12-15) ether sodium phosphate (trade name: Phosphanol RS-610NA, Toho Chemical Industry made) can be exemplified. These may be used individually by 1 type, and may use 2 or more types together.

Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ether glycerol borate esters, polyoxyethylene alkyl Ether phosphate, sorbitan fatty acid ester, fatty acid glycerin ester, glycerin fatty acid ester, pentaerythritol fatty acid ester can be exemplified. In addition, a compound having a polyoxyethylene chain in the molecule and having surface activity (such as polyoxyethylene), or a compound having a polyoxyalkylene chain composed of oxyethylene and oxypropylene instead of the polyoxyethylene chain in the above compound Compounds can also be used. These may be used individually by 1 type, and may use 2 or more types together.

As the critical micelle concentration, the value of Surfactant Handbook, New Edition (2000, 4th edition, edited by Kogyo Tosho Co., Ltd.) can be adopted. For example, the critical micelle concentration of sodium n-dodecylbenzenesulfonate is 1.2 mmol/L (75°C), and the critical micelle concentration of disodium dioctylsulfosuccinate is 0.7 g/L (25°C).

The monomer mixture (a) has a solubility of 0.02% by mass or more in a medium containing water as a main component at 20°C, and the polymer is a monomer that does not dissolve in a medium containing water as a main component. It is a mixture of monomers. By using such a monomer mixture (a), seed polymerization proceeds easily, and the resulting polymer is less soluble in a medium, making it easier to obtain seed particles.

Examples of monomers used in the monomer mixture (a) include acrylic acids such as methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate. Alkyl esters, (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. can be exemplified by hydroxyl group-containing (meth)acrylic acid esters. These may be used individually by 1 type, and may use 2 or more types together.
From the viewpoint of polymerization stability, it is preferable to use a combination of methyl methacrylate and C4-C8 alkyl methacrylate in the monomer mixture (a).

Examples of water-soluble radical polymerization initiators include persulfates, water-soluble azo compounds, thermal decomposition polymerization initiators, and redox polymerization initiators.
Examples of persulfates include potassium persulfate, ammonium persulfate, and sodium persulfate. Examples of water-soluble azo compounds include 2,2'azobis(2-amidinopropane) trihydrochloride and 4,4'-azobis(4-cyanopentanoic acid). Examples of thermal decomposition polymerization initiators include hydrogen peroxide. Examples of redox polymerization initiators include hydrogen peroxide and ascorbic acid, tert-butyl hydroperoxide and Rongalite, potassium persulfate and metal salt, ammonium persulfate and sodium hydrogen sulfite. One of these polymerization initiators may be used alone, or two or more thereof may be used in combination.
As the water-soluble radical polymerization initiator, persulfates are preferable because they are suitable for soap-free polymerization that allows relatively large seed particles to be obtained.

(Step I (b))
In step I (b), a monomer mixture (b) containing methyl methacrylate and a specific amount of chain transfer agent are added dropwise to the polymer dispersion (A) in the presence of a water-soluble radical polymerization initiator. to polymerize. As a result, a polymer dispersion (B) containing particles in which the polymer dispersion (A) is coated with the polymer of the monomer mixture (b) is obtained.
The chain transfer agent may be mixed with the monomer mixture (b) and added dropwise, or may be added dropwise simultaneously with the monomer mixture (b).

Monomer mixture (b) contains methyl methacrylate. The monomer mixture (b) may contain other monomers exemplified in the description of the copolymer (X) in addition to methyl methacrylate.

By using a chain transfer agent in step I (b), the molecular weight of the copolymer (X) can be adjusted.
Examples of chain transfer agents include mercaptans such as n-dodecylmercaptan, primary or secondary mercapto compounds, thioglycolic acid esters such as octyl thioglycolate, α-methylstyrene dimer, and terpinolene. Among them, a primary or secondary mercapto compound is preferable from the viewpoint that the physical properties of the hot-melt adhesive using the powder composition of the present invention are improved.

Examples of primary or secondary mercapto compounds include alkylmercaptans, thioglycolic acid esters, and mercaptopropionic acid esters. Examples of alkyl mercaptans include n-butyl mercaptan, sec-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and n-octadecyl mercaptan. Examples of thioglycolic acid esters include 2-ethylhexyl thioglycolate, methoxybutyl thioglycolate, and trimethylolpropane tris (thioglycolate). Examples of mercaptopropionates include 2-ethylhexyl β-mercaptopropionate, 3-methoxybutyl β-mercaptopropionate, and trimethylolpropane tris (β-thiopropionate). Among them, n-octylmercaptan, n-dodecylmercaptan, and 2-ethylhexyl thioglycolate having a large chain transfer constant are preferred, and n-dodecylmercaptan and 2-ethylhexyl thioglycolate are more preferred in terms of odor. These may be used individually by 1 type, and may use 2 or more types together.

The amount of the chain transfer agent used is preferably 0.1 to 3 parts by mass, more preferably 0.3 to 2 parts by mass, per 100 parts by mass of the monomer mixture (b). If the amount of the chain transfer agent used is at least the above lower limit, the chain transfer of radicals reduces the molecular weight of the copolymer (X) and improves the adhesion to the substrate. Further, if the amount of the chain transfer agent used is equal to or less than the above upper limit, the residual amount of unreacted monomers and chain transfer agent is reduced, and the odor is reduced.

In step I (b), a radical polymerization initiator may be further added. As the radical polymerization initiator to be used, for example, the same water-soluble radical polymerization initiator as exemplified in step I(a) can be exemplified.
The total amount of the water-soluble radical polymerization initiator used in Step I (a) and Step I (b) is 0 with respect to the total amount of 100 parts by mass of the monomer mixture (a) and the monomer mixture (b). .1 part by mass or more is preferable, and 0.2 to 1.0 part by mass is more preferable. If the total amount of the water-soluble radical polymerization initiator used is at least the above lower limit, a powder composition having good solubility in polyalkylene glycol can be obtained, and the polymer composition dissolved in polyalkylene glycol can be obtained. Viscosity is lowered and handleability is improved.

An emulsifier may be used in step I (b). As the emulsifier used in step I(b), for example, the same emulsifiers as exemplified in the explanation of step I(a) can be exemplified.
The polymerization temperature in step I (a) and step (b) may be set according to the type of water-soluble radical polymerization initiator and polymerization conditions. For example, when a water-soluble inorganic peroxide such as potassium persulfate or ammonium persulfate is used alone as a water-soluble radical polymerization initiator, polymerization can be carried out at a temperature equal to or higher than the 10-hour half-life temperature of the polymerization initiator. . From the viewpoint of polymerization stability and shortening of time, the temperature is preferably 5° C. or more higher than the 10-hour half-life temperature of the water-soluble radical polymerization initiator.
The polymerization time in step I(a) and step (b) may be set according to the type of polymerization initiator and polymerization conditions. Although the appropriate polymerization time varies depending on the polymerization temperature, it is preferable to carry out the polymerization within the time during which the polymerization initiator can be thermally decomposed and radicals can be generated.

(Step II)
In step II, an alkaline compound is added to the polymer dispersion (B) obtained in step I(b) to obtain a polymer dispersion (B'). The method of adding the alkaline compound is not particularly limited, and it is preferable to add the alkaline compound as an aqueous solution from the viewpoint of suppressing a local increase in pH.
The content of the alkaline compound is preferably 0.005 parts by mass or more, more preferably 0.05 to 5 parts by mass, with respect to 100 parts by mass of the total amount of the monomer mixture (a) and the monomer mixture (b). , more preferably 0.05 to 4 parts by mass, and particularly preferably 0.05 to 3 parts by mass.

The pH of the polymer dispersion (B') after addition of the alkaline compound is preferably 4.0 or higher, more preferably 5.0 or higher, and even more preferably 5.5 or higher. The pH of the polymer dispersion (B') is preferably 13 or less, more preferably 12 or less, and even more preferably 11.5 or less. By setting the pH of the polymer dispersion liquid (B') within the above range, the decomposition products of the polyalkylene glycol during heating are suppressed, and the odor of the hot melt adhesive is reduced.

(Step III)
In step III, a powder composition containing an acrylic polymer is recovered from the polymer dispersion (B').
The method for recovering the powder composition from the polymer dispersion (B′) is not particularly limited, and examples thereof include a spray drying method (spray drying method), and a method of drying after acid coagulation or salt coagulation. The spray drying method is preferable because the primary particles are not strongly bonded to each other and the primary particles can be easily formed with a weak shearing force.

The powder composition obtained in Step III contains primary particles and secondary particles in which the polymer dispersion (A) is coated with the polymer of the monomer mixture (b). The higher-order structure of secondary particles is not particularly limited, and secondary structures such as primary particles aggregated with weak cohesion force, particles aggregated with strong cohesion force, and particles fused together by heat are possible. is. Furthermore, by subjecting these secondary particles to a treatment such as granulation, it is possible to give them a higher-order structure.
The above-mentioned higher-order structure, for example, suppresses powder dusting and increases fluidity, and can be performed for the purpose of improving workability, and improves the dispersion state of powder in polyalkylene glycol. etc. can also be carried out to improve physical properties, and it is possible to design according to the application and requirements.

<<Polymer composition>>
The polymer composition of the present invention may contain a powder composition containing the acrylic polymer of the present invention and polyalkylene glycol as a polyol component.

(polyalkylene glycol)
Examples of polyalkylene glycol include structural units derived from two or more glycols such as polymethylene glycol, polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, polyhexamethylene glycol, and copolymers of ethylene oxide and propylene oxide. branched polyalkylene glycol using a polyfunctional alcohol such as glycerin. These may be used individually by 1 type, and may use 2 or more types together.

The number average molecular weight of the polyalkylene glycol is preferably 200-5000, more preferably 700-3000. When the number average molecular weight of the polyalkylene glycol is at least the above lower limit, the adhesive strength of the hot-melt adhesive after curing will be good. When the number average molecular weight of the polyalkylene glycol is equal to or less than the upper limit, the viscosity of the polymer composition will be low and the coatability will be good.

(polyester polyol)
The polymer composition of the invention may further contain a polyester polyol. Crystalline polyester polyols and amorphous polyester polyols are known as polyester polyols. Specific examples include aliphatic polyester polyols and aromatic polyester polyols.
Crystalline and amorphous polyester polyols are also readily distinguished by differential scanning calorimetry (DSC). More specifically, the melting point of the crystalline polyester polyol is observed by DSC as an endothermic peak when the temperature is raised, and as an exothermic peak when the temperature is lowered. When the melting point of the amorphous polyester polyol is measured by DSC, no endothermic peak or exothermic peak is clearly observed, so that it can be distinguished from the crystalline polyester polyol.

Aliphatic polyester polyols can be obtained by reacting aliphatic dicarboxylic acids with diols.
Examples of aliphatic dicarboxylic acids include adipic acid, sebacic acid, azelaic acid, and decamethylenedicarboxylic acid. One type of aliphatic dicarboxylic acid may be used alone, or two or more types may be used in combination.
Examples of diols include ethylene glycol, 1-methylethylene glycol, 1-ethylethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, and neopentyl. Low molecular weight diols having 2 to 12 carbon atoms such as glycol, 2-methyl-1,3-propanediol, cyclohexanedimethanol and 2,4-dimethyl-1,5-pentanediol can be exemplified. Among them, one or more of ethylene glycol, butanediol, hexanediol, octanediol and decanediol are preferable. One diol may be used alone, or two or more diols may be used in combination.

Examples of aliphatic polyester polyols include polyhexamethylene adipate, polyhexamethylene sebacate, polyhexamethylene dodecanate, and polybutylene adipate.

The aromatic polyester polyol is preferably a compound obtained by reacting an aromatic polycarboxylic acid or an aromatic dicarboxylic acid with the diol. Examples of aromatic polycarboxylic acids or aromatic dicarboxylic acids include phthalic acid, isophthalic acid, and terephthalic acid. These may be used individually by 1 type, and may use 2 or more types together.
Examples of aromatic polyester polyols include polyalkylene phthalates, polyalkylene isophthalates, and polyalkylene terephthalates.

A polyester polyol has a low viscosity, is easy to handle, and is suitable for dissolving a powder composition containing an acrylic polymer. In addition, since polyester polyol has high heat resistance and solvent resistance and high strength, it is preferable to use polyalkylene glycol and polyester polyol together.

(isocyanate)
The polymer composition of the invention may further contain an isocyanate.
Isocyanates include, for example, ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2 -diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5 -naphthylene diisocyanate, diphenyl-4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfuridene diisocyanate, 1-chlorobenzene-2,4- Diisocyanates, 4,4′,4″-triisocyanate-triphenylmethane, 1,3,5-triisocyanate-benzene, 2,4,6-triisocyanate-toluene and 4,4′-dimethyldiphenylmethane-2,2 ',5,5'-Tetraisocyanate can be exemplified.

The isocyanate is preferably a compound having an average of 1 to 3 isocyanate groups per molecule, and more preferably a bifunctional isocyanate, a so-called diisocyanate. One type of isocyanate may be used alone, or two or more types may be used in combination. Among them, 4,4'-diphenylmethane diisocyanate is preferred because of its high adhesive strength after moisture curing.

Although monools, monoisocyanates, trifunctional polyols and trifunctional isocyanates can also be used, a combination of a difunctional polyol (diol) and a difunctional isocyanate (diisocyanate) is preferred in view of the viscosity of the polymer composition. preferable.
It should be noted that it is preferable to use 2 mol of difunctional isocyanate for 1 mol of difunctional polyol, because the desired urethane prepolymer can be produced relatively easily.

The polymer composition of the present invention can contain other additives as long as they do not adversely affect the reaction between the polyol and the isocyanate that form the urethane prepolymer. Examples of additives include plasticizers, antioxidants, pigments, light stabilizers, flame retardants, curing catalysts, and waxes. Moreover, a wetting agent, a thickening agent, an antifoaming agent, a rheology control agent, etc. can be added as necessary.
The content of the additive with respect to the total mass of the polymer composition of the present invention is preferably 0 to 5% by mass.

The polymer composition of the present invention preferably has an odor evaluation value of 100,000,000 or less, more preferably 65,000,000 or less, as measured by the odor evaluation method described later, and more preferably 25,000,000. 000 or less is more preferable. If the odor evaluation value is within the above range, the lower the value, the lower the odor when the polymer composition of the present invention is heat-melted and used as a hot-melt adhesive, so coating workability is good. becomes.

(Odor evaluation method)
Powder composition containing acrylic polymer/polypropylene glycol (number average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 20/80 (mass%), on a water bath at 80 ° C. Stir for 60 minutes to dissolve the powder composition in the polypropylene glycol. The stirring is carried out at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm and a total height of 95 mm.
0.1 g of the resulting solution is weighed into a 20-mL vial, sealed, heated at 140° C. for 2 hours, and the generated gas is measured by headspace GC/MS. Thereafter, ion extraction is performed at m/z=87, and the odor evaluation value is obtained by dividing the peak area with a retention time of 2.8 to 3.2 minutes by the sample amount (g) and volume of 20 mL. The analysis conditions for headspace GC/MS are as follows.
<Analysis conditions>
Measuring machine: GC/MS 7890B/5977A manufactured by Agilent Technology
Column: UA-5 manufactured by Frontier Lab (30 m × 0.25 mm I.D. film thickness 0.25 μm)
Column temperature: 40 ° C. (held for 5 min) → 10 ° C./min temperature increase → 300 ° C. (held for 5 min)
Carrier gas: He (flow rate: 1.0 mL/min)
Inlet mode: split (split ratio 100:1)
Inlet temperature: 280°C
Transfer line temperature: 280°C
Injection volume: 250 μL

(Method for producing polymer composition)
The polymer composition of the present invention is obtained by dissolving the powder composition containing the acrylic polymer obtained by the production method of the present invention in polyalkylene glycol. As a method of dissolving the powder composition, for example, a method of adding the powder composition to polyalkylene glycol, dispersing it, and then heating and mixing can be exemplified.

The heating temperature is not particularly limited as long as it is a temperature at which the powder composition containing the acrylic polymer dissolves. It can be dissolved at low temperature or in a short time.

When the polyester polyol is blended, the powder composition containing the acrylic polymer and the polyester polyol may be added at the same time or dissolved separately. Then, if necessary, a defoaming agent is added, and the mixture is stirred while being heated under reduced pressure using a vacuum pump or the like to sufficiently remove moisture in the polymer composition.

When blending isocyanate, a urethane prepolymer can be obtained by dissolving a powder composition containing an acrylic polymer in polyalkylene glycol, adding isocyanate, and heating and mixing. Furthermore, when a polyester polyol is blended, the polyester polyol may be added to the polyalkylene glycol together with the powder composition and mixed under heat, or may be added together with the isocyanate and mixed under heat. Moreover, the polyester polyol may be added separately from the powder composition and the isocyanate and mixed with heating.

When adding an additive, the timing of adding the additive is not particularly limited. For example, it may be added together with the polyol and isocyanate when synthesizing the urethane prepolymer, or may be added after the polyol and isocyanate are reacted to synthesize the urethane prepolymer.

≪Hot melt adhesive≫
In the present invention, "hot melt adhesive" means an adhesive that is melted by heating at 80 to 150°C before use.
The hot melt adhesive of the invention comprises the polymer composition of the invention. When the hot-melt adhesive of the present invention contains the polymer composition of the present invention, the odor is reduced when the hot-melt adhesive is melted by heating and used as a hot-melt adhesive, resulting in good coating workability.

When the hot melt adhesive contains a powder composition containing an acrylic polymer, a polyester polyol and an isocyanate, the acrylic It is preferable that the powder composition containing the polymer is 1 to 50 parts by mass, and the total amount of polyester polyol and isocyanate is 50 to 99 parts by mass. More preferably, the powder composition containing the acrylic polymer is 5 to 30 parts by mass, and the total amount of the polyester polyol and isocyanate is 70 to 95 parts by mass. If the powder composition containing the acrylic polymer is at least the above lower limit, the initial adhesive strength tends to be good. Moreover, when the powder composition containing the acrylic polymer is equal to or less than the above upper limit, the adhesion strength after curing tends to be improved.

(Method for producing hot melt adhesive)
As a method for producing a hot melt adhesive, the step (IV) of dissolving the powder composition containing the acrylic polymer obtained by the production method of the present invention in polyalkylene glycol to obtain a polymer composition; A method comprising the step (V) of mixing isocyanate with the polymer composition to obtain a urethane prepolymer is preferred.

In step (IV), the same production conditions as those described in the production method of the polymer composition can be employed.
In (V) above, a curing catalyst may be further mixed. Examples of curing catalysts include 2,2′-dimorpholinodiethyl ether.

The hot-melt adhesive of the present invention can be used in the same manner as conventional hot-melt adhesives, and the method of use is not particularly limited.
The heating temperature for melting the hot melt adhesive is preferably 80 to 140.degree. C., more preferably 90 to 110.degree. When the temperature is within the above range, the respective components are well dissolved, the viscosity of the hot melt adhesive is lowered, and the handleability is improved. Furthermore, the reaction of isocyanate and polyalkylene glycol proceeds sufficiently.
The heating time is not particularly limited, but is preferably 30 minutes to 300 minutes, more preferably 60 minutes to 180 minutes.

The hot-melt adhesive of the present invention can be used in fields where hot-melt adhesives have been conventionally used, such as the field of architectural interiors (or architecture), the field of electronic materials, and the field of automobile interiors. Specifically, for example, it can be used as an adhesive for attaching automotive interior members, attaching decorative materials to architectural interior members, woodworking, paper processing, fiber processing, and general-purpose adhesives.

For example, when attaching an adherend to a base material, the hot melt adhesive may be applied to one or more surfaces of the base material side and the adherend side.
Usual adherends and substrates can be used, and examples thereof include molding materials, film sheets, and fibrous materials made by knitting synthetic fibers or natural fibers with a spinning machine to form a sheet.

Raw materials for molding materials, films and sheets are not particularly limited, and thermoplastic resins are preferred. Examples of raw materials for molding materials, films and sheets include polyolefin resins, polyester resins, acetate resins, polystyrene resins, ABS resins, vinyl chloride resins, and polycarbonate resins. Examples of the polyolefin resin include polyethylene and polypropylene. Examples of the polyester resin include polyethylene terephthalate.

A laminate obtained by laminating an adherend and a substrate with the hot-melt adhesive of the present invention can be used in various applications such as construction, electronic materials, and automobile fields. It is not necessary to use special equipment to manufacture the laminated product, and it can be manufactured using generally known manufacturing equipment including conveyors, coaters, presses, heaters and cutters. For example, laminates can be produced as follows. The hot-melt adhesive of the present invention is applied to the substrate or the adherend by a coater while the substrate and the adherend are being conveyed by a conveyor. The temperature during application is controlled to a predetermined temperature by a heater. The adherend is lightly pressed against the substrate with a press, and the adherend and the substrate are bonded together via a hot-melt adhesive. After that, the bonded adherend and base material are allowed to cool, and the hot-melt adhesive is solidified by being conveyed as it is. After that, the substrate to which the adherend has been attached is cut to an appropriate size by a cutting machine.

In the laminate, the hot melt adhesive of the present invention has high initial adhesive strength and excellent heat resistance after moisture curing, so that the substrate and the adherend are less likely to separate even in summer. In addition, it is also possible to manufacture a laminate by applying an adhesive without using a coater.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited by the following description.

Various measurement methods and evaluation methods are shown below.

(mass average molecular weight)
A polystyrene conversion value measured under the following conditions by a GPC (gel permeation chromatography) method was defined as the mass average molecular weight of the polymer.
<Measurement conditions>
・ High-speed GPC device (manufactured by Tosoh Corporation, product name: HLC-8220GPC)
・ Four columns (manufactured by Tosoh Corporation, product name: TSKgel SuperHZM-M) are connected in series and used ・ Oven temperature: 40 ° C.
・ Eluent: tetrahydrofuran ・ Sample concentration: 0.1% by mass
・Flow rate of eluent: 0.35 mL/min ・Injection volume of sample: 1 μL
・Detector: RI (differential refractometer)

(Volume average particle size)
Using a laser diffraction/scattering particle size distribution analyzer (manufactured by Horiba, product name: LA-960), the particle size of the obtained powder composition containing the acrylic polymer was measured. A median diameter (volume average particle diameter) was used as the particle diameter. The relative refractive indices of the resin particles and the dispersion medium were all set to 1.12. Ion-exchanged water was used as the dispersion medium.

(PPG solubility)
Powder composition containing acrylic polymer / polypropylene glycol (hereinafter also referred to as PPG, number average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 10/90 (mass%), The powder composition was dissolved in polypropylene glycol by stirring at 60° C. for 60 minutes. Stirring was performed at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm, and a total height of 95 mm. After that, the appearance was observed, and the presence or absence of insoluble components with a diameter of 1 mm or more was determined visually, and evaluated according to the following criteria.
<Evaluation Criteria>
○: There is no insoluble component with a diameter of 1 mm or more ×: There is an insoluble component with a diameter of 1 mm or more

(Odor evaluation when PPG solution is heated)
A powder composition containing an acrylic polymer/polypropylene glycol (number average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 20/80 (mass%), and stirred at 80°C for 60 minutes. Then, the powder composition was dissolved in polypropylene glycol. Stirring was performed at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm, and a total height of 95 mm.
0.1 g of the resulting solution was weighed into a 20-mL vial, sealed, heated at 140° C. for 2 hours, and the generated gas was measured by headspace GC/MS. After that, ion extraction is performed at m/z = 87, and the numerical value obtained by dividing the peak area with a retention time of 2.8 to 3.2 minutes by the sample amount (g) and volume of 20 mL is taken as the odor evaluation value, and is evaluated according to the following criteria. did. The analysis conditions for headspace GC/MS are as follows.
<Analysis conditions>
Measuring machine: GC/MS 7890B/5977A manufactured by Agilent Technology
Column: UA-5 manufactured by Frontier Lab (30 m × 0.25 mm I.D. film thickness 0.25 μm)
Column temperature: 40 ° C. (held for 5 min) → 10 ° C./min temperature increase → 300 ° C. (held for 5 min)
Carrier gas: He (flow rate: 1.0 mL/min)
Inlet mode: split (split ratio 100:1)
Inlet temperature: 280°C
Transfer line temperature: 280°C
Injection volume: 250 μL
<Evaluation Criteria>
○: The odor evaluation value obtained by the analysis is 100,000,000 or less ×: The odor evaluation value obtained by the analysis exceeds 100,000,000

(Appearance when PPG solution is heated)
A powder composition containing an acrylic polymer/polypropylene glycol (mass average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 20/80 (mass%), stirred at 80°C for 60 minutes. Then, the powder composition was dissolved in polypropylene glycol. Stirring was performed at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm, and a total height of 95 mm. The resulting solution was transferred to a test tube, placed in a drying oven at 180° C. for 2 hours, and the appearance of the solution was visually observed to confirm the presence or absence of coloration, and evaluation was made according to the following evaluation criteria.
<Evaluation Criteria>
〇: Transparent with excellent appearance △: Pale yellow with usable appearance ×: Yellow with poor appearance

(initial adhesive strength)
Two flat bars (made of wood, width 1.7 cm, length 7.5 cm, thickness 1.5 mm) were prepared, and hot melt adhesive melted at 120°C was applied to one of the bars 1.5 cm x 1. The hot-melt adhesive was applied to an area of 0.7 cm, overlapped with another flat bar, sandwiched with a double clip, and allowed to stand for 5 minutes to cool and solidify the hot-melt adhesive. After standing, the double clip was removed, and a tensile shear test was performed under the following measurement conditions using a precision universal testing machine (product name: AGS-X, manufactured by Shimadzu Corporation) as a tensile tester to measure the initial adhesive strength.
<Measurement conditions>
Tensile speed: 5.0mm/min
Distance between chucks: 50mm

(How to measure open time)
A hot-melt adhesive dissolved by heating was applied to a dried flat bar (wooden, 1.7 cm wide, 7.5 cm long, 1.5 mm thick) and heated to 120°C in a gear oven. After that, at room temperature, at intervals of 1 minute, pressure was applied with a finger to stick a piece of kraft paper, and the piece of kraft paper was quickly peeled off. The open time was defined as the time from when the hot-melt adhesive was applied to the flat bar to when no paper fibers remained on the adhesive surface when the piece of kraft paper was peeled off.

(Example 1) Powder composition containing acrylic polymer (P-1)
[Step I (a)]
Put 583 g of ion-exchanged water into a 2-liter four-necked flask equipped with a thermometer, a nitrogen gas inlet tube, a stirring rod, a dropping funnel, and a cooling tube, and pass nitrogen gas through for 30 minutes to remove dissolved oxygen in the ion-exchanged water. replaced. Then, nitrogen gas was stopped, and the temperature was raised to 80° C. while stirring at 200 rpm. When the internal temperature reached 80° C., a monomer mixture (a-1) consisting of 26 g of methyl methacrylate and 20 g of n-butyl methacrylate was added all at once, and 0.80 g of potassium persulfate and 20 g of ion-exchanged water were added. It was charged and held for 45 minutes to obtain a polymer dispersion (A-1).

[Step I (b)]
1.38 g of Neoperex G-15 (sodium dodecylbenzenesulfonate, active ingredient (emulsifier) 15%, manufactured by Kao Corporation) and ion A mixed solution of 3.51 g of exchanged water and then a mixed solution of 0.4 g of potassium persulfate and 10 g of ion-exchanged water were added, and after 15 minutes, 526 g of methyl methacrylate, 215 g of n-butyl methacrylate, 9.6 g of methacrylic acid, A monomer mixture (b) consisting of 3.2 g of hydroxyethyl methacrylate, 5.92 g of phosphanol RS-610NA, 14.4 g of n-dodecylmercaptan and 400 g of deionized water was added dropwise over 5 hours. After completion of the dropwise addition, the temperature was kept at 80° C. for 1 hour to complete the polymerization, thereby obtaining a polymer dispersion (B-1). Polymerization was carried out in an environment in which 25 mL of nitrogen gas was passed per minute.

[Step II]
After cooling the polymer dispersion (B-1) obtained in step I (b) to room temperature, 1.84 g of a KOH aqueous solution adjusted to a concentration of 5% by mass was added to polymer dispersion (B'-1). ). The pH of the polymer dispersion (B'-1) was 4.0.

[Step III]
Using a spray dryer (manufactured by Okawara Kakoki Co., Ltd., product name: L-8i type), the polymer dispersion (B'-1) was prepared under the conditions of an inlet temperature of 150 ° C., an outlet temperature of 60 ° C., and a disk rotation speed of 20,000 rpm. ) was spray-dried to obtain a powder composition (P-1) containing an acrylic polymer.
The powder composition (P-1) containing an acrylic polymer had a mass average molecular weight of 43,000, a volume average particle size of primary particles of 0.553 μm, and a volume average particle size of secondary particles of 54.1 μm.
Table 4 shows the evaluation results.

(Examples 2 to 6) Powder compositions containing acrylic polymers (P-2 to P-6)
A powder composition containing an acrylic polymer (P-2 to P-6) was produced in the same manner as in Example 1, except that the amount of the 5 mass% KOH aqueous solution was changed as shown in Table 1. . Table 4 shows the evaluation results.

(Comparative Example 1) Powder composition containing acrylic polymer (P-7)
A powder composition (P-7) containing an acrylic polymer was produced in the same manner as in Example 1, except that the 5% by mass KOH aqueous solution was not blended. Table 4 shows the evaluation results.

(Examples 7 to 9) Powder compositions containing acrylic polymers (P-8 to P-10)
A powder composition containing an acrylic polymer (P-8 to P-10) was produced. Table 5 shows the evaluation results.

(Examples 10 to 11) Powder compositions containing acrylic polymers (P-11 to P-12)
A powder composition containing an acrylic polymer (P-11 to P-12) was produced. Table 6 shows the evaluation results.

Abbreviations in Tables 1 to 3 indicate the following compounds.
・ “MMA”: Methyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
・ “n-BMA”: n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
・ “MAA”: methacrylic acid (manufactured by Mitsubishi Chemical Corporation)
・ “2-HEMA”: 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
・ “n-DM”: n-dodecyl mercaptan (manufactured by NOF Corporation)
・ “KPS”: Potassium persulfate (Mitsubishi Gas Chemical Co., Ltd.)
・ “G-15”: Neopelex G-15, sodium dodecylbenzenesulfonate, active ingredient (emulsifier) 15% (manufactured by Kao Corporation)
・ “RS-610NA”: Phosphanol RS-610NA, polyoxyethylene alkyl (12-15) ether sodium phosphate

As shown in Tables 4 to 6, the polymer compositions using the powder compositions containing the acrylic polymers of Examples 1 to 11 obtained by the production method of the present invention had low odor that could cause odor when heated. The generation of molecular weight components was suppressed, the odor was low, and the appearance was good.
On the other hand, the polymer composition using the powder composition containing the acrylic polymer of Comparative Example 1, in which no alkaline compound was added to the polymer dispersion obtained in step I (b), had a low odor that could cause odor when heated. A large amount of molecular weight components was generated, the odor was very strong, and the appearance was poor.

(Example 12)
[Dissolving process]
A 300 mL four-necked flask equipped with a thermometer, a stir bar, and a cooling tube was charged with 41.1 g of polypropylene glycol having a mass average molecular weight of about 2000 as a polyol (trade name ADEKA POLYETHER P-2000, manufactured by ADEKA), and a mass average molecular weight of About 400 polypropylene glycol (trade name ADEKA POLYETHER P-400, manufactured by ADEKA) 3.0 g, "Modaflow 2100" (manufactured by Allnex) 0.3 g as a defoaming agent, a powder composition containing an acrylic polymer (P -3) 23.7 g was added, the internal temperature was heated to 100° C., and the mixture was stirred for 1 hour to obtain a uniform polymer composition in the form of a solution.

[Reduced pressure dehydration step]
The polymer composition was heated and stirred at 15 kPa and 100° C. for 1 hour and dehydrated under reduced pressure.
24.5 g of polyester polyol "HS 2H-351A" (manufactured by Toyokuni Oil, polyester polyol of hexanediol and adipic acid, molecular weight 3500, melting point 55°C, hydroxyl value = 32 mgKOH/g) as polyol, 4,4'-diphenylmethane as isocyanate 14.0 g of diisocyanate and 0.1 g of 2,2′-dimorpholinodiethyl ether (manufactured by Mitsui Chemicals Fine Co., Ltd.) as a curing catalyst were added and stirred at 15 kPa and 100° C. for 3 hours. After cooling, the resulting hot-melt adhesive was recovered and sealed for storage.
Table 7 shows the measurement results of initial adhesive strength and open time.

(Examples 13-14)
A hot melt adhesive was obtained in the same manner as in Example 12, except that the type of powder composition containing an acrylic polymer was changed as shown in Table 7. Table 7 shows the measurement results of initial adhesive strength and open time.

As shown in Table 7, the hot melt adhesives of Examples 12 to 14 using the powder composition containing the acrylic polymer obtained by the production method of the present invention had good initial strength and open time. Indicated.

According to the present invention, there is provided a powder composition containing an acrylic polymer, which is less odorous than conventional products, has a low environmental load, and is suitable for hot-melt adhesives that are transparent and have good appearance. can be done. Therefore, the powder composition containing the acrylic polymer of the present invention can be suitably used in fields where hot-melt adhesives have been conventionally used, such as the field of building interiors, the field of electronic materials, and the field of automobile interiors. Extremely important.

Claims (18)

A powder composition containing an acrylic polymer containing a copolymer having a structural unit derived from a (meth)acrylic monomer and an alkaline compound, wherein the secondary particles have a volume average particle size of 20 to 80 μm. 2. The powder composition according to claim 1, wherein the primary particles have a volume average particle size of 0.1 to 10 μm. 3. The powder composition according to claim 1, which has a mass average molecular weight of 10,000 to 500,000. The powder composition is soluble when the powder composition is mixed with polypropylene glycol having a number average molecular weight of 1000 to a concentration of 10% by mass and stirred at 60° C. for 60 minutes. 4. The powder composition according to any one of 1 to 3. The powder composition according to any one of claims 1 to 4, wherein the alkaline compound is an alkali metal or alkaline earth metal hydroxide. The powder composition according to any one of claims 1 to 5, wherein the content of the alkaline compound is 0.005 parts by mass or more with respect to 100 parts by mass of the copolymer. A polymer composition comprising the powder composition according to any one of claims 1 to 6 and a polyalkylene glycol. The polymer composition according to claim 7, wherein the polyalkylene glycol has a number average molecular weight of 200-5000. 9. The polymer composition according to claim 7 or 8, which has an odor evaluation value of 100,000,000 or less as measured by the following odor evaluation method.
(Odor evaluation method)
Powder composition containing acrylic polymer/polypropylene glycol (number average molecular weight 1000, trade name: ADEKA POLYETHER P-1000, manufactured by ADEKA) = 20/80 (mass%), on a water bath at 80 ° C. Stir for 60 minutes to dissolve the powder composition in the polypropylene glycol. The stirring is carried out at 250 rpm using a magnetic stirrer and an octagon stirrer with a diameter of 8 mm and a length of 40 mm, using a glass sample bottle with a full volume of 144 mL, a barrel diameter of 55 mm and a total height of 95 mm.
0.1 g of the resulting solution is weighed into a 20-mL vial, sealed, heated at 140° C. for 2 hours, and the generated gas is measured by headspace GC/MS. Thereafter, ion extraction is performed at m/z=87, and the odor evaluation value is obtained by dividing the peak area with a retention time of 2.8 to 3.2 minutes by the sample amount (g) and volume of 20 mL. The analysis conditions for headspace GC/MS are as follows.
<Analysis conditions>
Measuring machine: GC/MS 7890B/5977A manufactured by Agilent Technology
Column: UA-5 manufactured by Frontier Lab (30 m × 0.25 mm I.D. film thickness 0.25 μm)
Column temperature: 40 ° C. (held for 5 min) → 10 ° C./min temperature increase → 300 ° C. (held for 5 min)
Carrier gas: He (flow rate: 1.0 mL/min)
Inlet mode: split (split ratio 100:1)
Inlet temperature: 280°C
Transfer line temperature: 280°C
Injection volume: 250 μL Polymer composition according to any one of claims 7 to 9, further comprising a polyester polyol. A polymer composition according to any one of claims 7 to 10, further comprising an isocyanate. A hot melt adhesive comprising the polymer composition according to any one of claims 7-11. A method for producing a powder composition containing an acrylic polymer, comprising the following steps I to III.
[Step I]
(a) in a medium containing water as a main component, in the presence of an emulsifier having a critical micelle concentration or less and a water-soluble radical polymerization initiator, having a solubility of 0.02% by mass or more in the medium at 20°C; and polymerizing the monomer mixture (a), the polymer of which is insoluble in the medium, to obtain a polymer dispersion (A). Then, (b) a monomer mixture (b) containing methyl methacrylate for the polymer dispersion (A), and 0.1 to 0.1 parts per 100 parts by mass of the monomer mixture (b) 3 parts by mass of a chain transfer agent is dropped and polymerized to obtain a polymer dispersion (B). However, the total amount of the water-soluble radical polymerization initiator used in (a) and (b) is based on the total amount of 100 parts by mass of the monomer mixture (a) and the monomer mixture (b) It is 0.1 parts by mass or more.
[Step II]
An alkaline compound is added to the polymer dispersion (B) to obtain a polymer dispersion (B').
[Step III]
A powder composition is obtained from the polymer dispersion (B′). 14. The method for producing a powder composition according to claim 13, wherein the polymer dispersion (B') has a pH of 4.0 or higher. 15. The method for producing a powder composition according to claim 13 or 14, wherein the water-soluble radical polymerization initiator is a persulfate. A method for producing a polymer composition, comprising the step of dissolving the powder composition obtained by the production method according to any one of claims 13 to 15 in polyalkylene glycol. A step of dissolving the powder composition obtained by the production method according to any one of claims 13 to 15 in polyalkylene glycol to obtain a polymer composition, and further mixing isocyanate to produce a urethane prepolymer. A method for producing a polymer composition, comprising the step of obtaining. 18. The method of making a polymer composition according to Claim 17, wherein the polymer composition is a hot melt adhesive.