KR20220029323A - Resin powder and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a method for preparing resin powder having a low content of foreign materials and impurities. The method for preparing resin powder according to the present invention includes: a core polymerization step of emulsifying a first monomer mixture containing an acrylic monomer with a phosphate-based emulsifier and carrying out emulsion polymerization to polymerize a core dispersed in the emulsion phase; a shell polymerization step of introducing a second monomer mixture having a composition different from the composition of the first monomer mixture to the emulsion, thereby forming a first shell containing an emulsified polymer polymerized from the second monomer mixture on the core; a coagulation step of allowing the core-shell polymer polymerized from the shell polymerization step to be in contact with a coagulating agent containing a water soluble salt of alkali metal or alkaline earth metal so that the core-shell polymer may be coagulated; and an impurity-removing step of removing an insoluble salt formed through the reaction of the phosphate-based emulsifier with the coagulating agent by using an acidic aqueous dissociating agent solution.

Description

Resin powder and resin powder manufacturing method {Resin powder and manufacturing method thereof}

One aspect of the present invention relates to a resin powder, and more particularly, to a resin powder prepared by emulsion polymerization and a method for preparing the same.

Acrylic resin is excellent in transparency, weather resistance, etc., and the appearance of the molded body is good, so it is widely used for electric parts, vehicle parts, optical parts, ornaments, signboards, etc. For example, acrylic resin is molded into a film form An acrylic resin film is widely used as a surface material to be laminated on the surface of various articles because of its good flexibility and workability.

As a raw material for acrylic resin film, various resin compositions have been proposed so far, and many resin compositions are used. Among them, it has excellent weather resistance, transparency, and stress whitening resistance such as bending whitening resistance. As a raw material for acrylic resin film suitable for skin marking film, high-brightness reflective material coating film, etc., for use in building materials such as window frames, width wooden bathroom interiors, etc., multi-layers with a specific structure composed of alkyl acrylate and alkyl methacrylate as components Structural polymers are known

Such a multi-layered polymer is prepared by dispersing a polymerizable monomer in water containing an emulsifier and polymerizing the polymerizable monomer in micelles having an emulsifier molecular layer on the surface to produce an emulsion polymerization latex in which polymer particles are dispersed in water. is manufactured

In Korea, various companies including LG are conducting research and development on emulsion polymerized latex resin particles to manufacture acrylic resins such as MMA. There are many difficulties in development.

When using the conventional resin powder manufacturing method, foreign substances or impurities generated in the process of solidifying the emulsion polymer may be included in the final resin powder. In particular, alkaline earth metals, calcium, sulfur, etc. produced by emulsion polymerization of monomer There have been problems in that the transparency of the product is lowered, physical properties are lowered, and the number of yellowing degree is increased because it is included in the copolymer latex. .

Republic of Korea Patent No. 10-0375588

One aspect of the present invention is to solve the problem that the content of foreign substances contained in the copolymer latex prepared through emulsion polymerization of acrylic monomers is small, and in particular, calcium salt, which is an insoluble salt, remains as impurities in the resin powder. An object of the present invention is to provide a resin powder manufacturing method and a resin powder manufactured by the manufacturing method with a low content of foreign substances and impurities.

In addition, a process capable of easily removing foreign substances from the product by dissociating foreign substances generated during the emulsion polymerization manufacturing process of the monomer easily without using an expensive additional process and a removal means for removing foreign substances are provided. It is an object of the present invention to

In addition, it is an object of the present invention to economically manufacture a resin powder having good physical properties such as elasticity and shock absorption and excellent optical properties such as yellowing degree.

One aspect of the present invention is a core polymerization step of emulsifying a first monomer mixture containing an acrylic monomer with a phosphoric acid-based emulsifier, followed by emulsion polymerization in a reaction vessel to polymerize the core dispersed in the emulsion phase;

a shell polymerization step of synthesizing a first shell including an emulsion polymer polymerized from the second monomer mixture on the core by introducing a second monomer mixture having a composition different from that of the first monomer mixture into the reaction vessel;

a coagulation step of coagulating the core-shell polymer polymerized in the shell polymerization step by contacting it with a coagulant containing a water-soluble salt of an alkali metal or alkaline earth metal; and

an impurity removal step of removing the insoluble salt produced by the reaction of the phosphoric acid-based emulsifier and the coagulant with an aqueous acidic dissociating agent; It is a resin powder manufacturing method comprising a.

At this time, the shell polymerization step is,

With respect to a natural number n of 2 or more, an emulsion polymer polymerized from the (n+1)th monomer mixture on the core-shell polymer by adding a (n+1)th monomer mixture having a composition different from the nth monomer mixture It is better to further include the step of synthesizing the n-th shell,

The first monomer mixture to the (n+1)th monomer mixture are acrylic monomers such as methyl methacrylate (MMA), butyl acrylate (BA), ethylene glycol dimethacrylate (EGMA) and aryl methacrylate (AMA). ) it is good to include at least any one or more selected from the group consisting of,

Preferably, the second monomer mixture to the (n+1)th monomer mixture include the methyl methacrylate (MMA) and the butyl acrylate (BA).

In addition, the weight ratio (MMA/BA) of methyl methacrylate and butyl acrylate contained in the (n+1)-th monomer mixture is the weight ratio of methyl methacrylate and butyl acrylate in the n-th monomer mixture ( Better than MMA/BA),

The acidic dissociating agent aqueous solution preferably has a pH of 2 to 4,

The aqueous acid dissociating agent is preferably an aqueous inorganic acid solution.

In addition, the coagulant preferably contains 1 to 20% by weight of the water-soluble salt of the alkali metal or alkaline earth metal,

Preferably, in the core polymerization step, a solution containing a catalyst or an additive is stirred in the reaction vessel, and the first monomer mixture is introduced into the reaction vessel,

The phosphoric acid-based emulsifier preferably includes a phosphoric acid ester salt represented by the following General Formula 1 or the following General Formula 2.

(General formula 1)

(General formula 2)

(In Formulas 1 and 2, R is a linear or branched alkyl group having 10 to 18 carbon atoms, M is an alkali metal or alkaline earth metal element, and n is an integer of 1 to 20 that is the same or different from each other.)

Another aspect of the present invention is a resin powder prepared by the above-described resin powder manufacturing method,

As a resin powder having an average particle diameter of 0.3 to 200 μm of impurities contained in the resin powder,

The resin powder is a core; and

Including; at least one shell provided on the core;

It is preferable that the composition of the monomers included in the core and the polymer constituting the resin are different from each other,

In another aspect, a resin molded article prepared by adding a compounding agent to the above-mentioned resin powder and molding by any one or more methods of an extrusion method, an injection molding method, a vacuum molding method, a blow molding method, or a compression molding method may be provided.

According to one aspect of the present invention, the resin powder manufacturing method of the present invention includes a core-shell structure having two or more layers by dividing the monomer mixture used for polymerization several times with different compositions and performing polymerization, and includes a core-shell structure during polymerization or solidification. Since the generated impurities or foreign substances are not included in the powder, a resin powder having high purity and uniform size can be manufactured.

In addition, in the case of manufacturing a resin powder by an emulsion polymerization method using phosphoric acid and a phosphoric acid ester-based emulsifier, insoluble salts that are included in the resin powder and deteriorate the appearance characteristics of products and products are washed with an acidic dissociative solution containing an inorganic acid. Since dissociation through the steps, the amount of insoluble salt contained in the product is reduced, so that a resin powder having excellent purity and appearance characteristics can be provided.

In addition, the resin powder manufacturing method of the present invention produces a resin powder having a core-shell structure, and when it includes a shell of two or more layers, the composition of the monomer for synthesizing the shell satisfies a specific relationship, so that the resin powder has good elastic properties, It is suitable for use as a material for reinforcing impact.

In addition, the prepared resin powder has a low content of foreign substances such as insoluble salts, so that no separate filtering is required during molding, or filtering is easy even if filtering is required, thereby increasing filtering efficiency.

In addition, in the case of molding the resin powder, the fluidity and thermal stability of the resin are increased, the lifespan of the filter used during filtering is prolonged, so that the economical efficiency of the process is improved, and the quality of the molded article to be manufactured is excellent.

In addition, when using a resin powder containing a small amount of foreign substances, it has the advantage of providing a thermoplastic resin molded body, particularly an acrylic resin film, which has excellent design, high mechanical strength, is easy to handle, and can be applied to various uses.

1 is a cross-sectional view schematically showing the internal structure of a resin powder according to an embodiment of the present invention.

Before describing the present invention in detail below, it is to be understood that the terminology used herein is for the purpose of describing specific embodiments and is not intended to limit the scope of the present invention, which is limited only by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art, unless otherwise stated.

Throughout this specification and claims, unless stated otherwise, the term comprise, comprises, comprising is meant to include the stated object, step or group of objects, and steps, and any other object. , steps, or groups of objects or groups of steps are not used in the sense of exclusion.

On the other hand, various embodiments of the present invention may be combined with any other embodiments unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as preferred or advantageous.

Also, when an element is said to be "above/below" or "above/below" another element, this means not only when it is "directly above/under" another element, but also in the case of another element in the middle. Including cases where there is

In the present specification, the term latex is used in a broad sense including resin powders and molded articles including polymers formed by emulsion polymerization, and the term emulsion polymerization latex is interpreted to mean polymers or resins and resin powders prepared by emulsion polymerization. .

The method for preparing the resin powder of the present invention includes a preparation step, a polymerization step, a solidification step, and an impurity removal step, wherein the polymerization step more specifically includes a core polymerization step and a shell polymerization step, and the shell polymerization step is at least The coagulation step may be performed after being continuously repeated one or more times.

The preparation step is a step of preparing or mixing a mixture containing an acrylic monomer to prepare a reactant for the reaction. The reactant acrylic monomer mixture may include an acrylic monomer having a single chemical structure, but a mixture containing one or more acrylic monomers is preferable because the physical properties of the resulting product can be controlled.

The type of the acrylic monomer used is not limited, but, for example, from the group consisting of methyl methacrylate (MMA), butyl acrylate (BA), ethylene glycol dimethacrylate (EGMA) and aryl methacrylate (AMA). It is preferable that at least any one or more selected is used.

When at least any one or more of the acrylic monomers included in the above-mentioned group is used, there is an advantage in that the elasticity and hardness of the prepared resin powder are appropriate, and transparency and physical properties are excellent during product manufacturing.

The reactant prepared in the preparation step may include an initiator. A radical initiator and a redox initiator may be used as the initiator, but a radical initiator is preferably used.

Peroxide is preferably used as the radical initiator, and examples of the peroxide initiator include hydrogen peroxide, t-butyl cumyl peroxide, and t-butylhydroperoxide (t-BH). and preferably t-butylhydroperoxide is used.

When t-butylhydroperoxide is used as an initiator, both large t-butoxide radicals and small hydroxide radicals can be obtained during emulsion polymerization. There is an advantage that can cause an efficient radical polymerization reaction.

In this case, the initiator is preferably included within 2 parts by weight, based on 100 parts by weight of the monomer mixture, within 1.0 parts by weight, preferably within 0.6 parts by weight.

When the content of the initiator is greater than the corresponding range, the initial reaction occurs rapidly and the number of chains increases rapidly, so the length of the polymer chains may be short after the completion of the reaction, and it may be difficult to keep the initial reaction temperature constant.

The polymerization step is a step of producing an acrylic polymer including an acrylic monomer from an acrylic monomer mixture as a reactant. An acrylic polymer or an acrylic copolymer including an acrylic monomer is obtained, and the product may contain some unreacted acrylic monomers. there is.

Hereinafter, when the term acrylic polymer is used, it is used to include all copolymers containing two or more acrylic monomers as well as a single monomer polymer.

The polymerization step is preferably a step in which an emulsifier for emulsion polymerization is mixed with the acrylic monomer mixture and stirred to form an emulsion to cause emulsion polymerization. During the emulsion polymerization of the polymerization step, the polymerization method is not limited, but it is preferable to include a general emulsion polymerization method in the art or an emulsion polymerization step that can be adopted by a person skilled in the art.

Specifically, in one embodiment of the present invention, an emulsion polymerization reaction is performed on the emulsion by injecting a mixture in which an acrylic monomer and an initiator for polymerization are mixed into a reactor (or reaction vessel) in which a solution containing an emulsifier is stirred.

An emulsifier is used to carry out the emulsion polymerization that occurs in the polymerization step, and the polymerization step includes emulsion polymerization of acrylic monomers using an emulsifier containing phosphoric acid or a phosphoric acid ester salt represented by the following general formula 1 or 2 Preferably, an emulsion polymer polymerized from an acrylic monomer is obtained as a reactant.

(General formula 1)

(General formula 2)

In the above general formulas 1 and 2, R represents a straight-chain or branched alkyl group having 10 to 18 carbon atoms. Here, the number of carbon atoms in the alkyl group is preferably 12 or more, and preferably 12 to 16 carbon atoms.

As a specific example, it is preferable that R is at least one or more selected from the group consisting of n-dodecyl group, n-tridecyl group, n-tetradecyl group and tridecyl group.

In addition, in General Formulas 1 and 2, M is an alkali metal or alkaline earth metal element, and sodium, potassium, lithium, rubidium, cesium, etc. may be used as the alkali metal, and calcium, barium, magnesium, strontium, etc. may be used as the alkaline earth metal. It is possible, and preferably, M is an element selected from the group consisting of sodium, potassium, calcium and barium.

Here, n is an integer of 1 to 20, preferably an integer of 3 to 18, and more preferably an integer of 4 to 10. Also, in Equation 1, n may be different integers, and may be the same integers.

The phosphoric acid ester salts represented by the general formulas 1 and 2 include, for example, polyoxyethylene nonylphenyl ether phosphate, polyoxyethylene, trithecyl ether phosphate, polyoxyethylene oleic ether phosphate, polyoxyethylene lauryl ether phosphate, Polyoxyethylene dodecylphenol ether phosphate, polyoxyethylene octylphenyl ether phosphate, polyoxyethylene monoaryl ether phosphate, polyoxyethylene neophenyl ether phosphate, polyoxyethylene neopentyl ether phosphate, polyoxyethylene bisphenol phosphate, ether polyoxyethylene glycerine ether phosphate, polyoxyethylene naphthyl ether phosphate, polyoxyethylene decyl ether phosphate, polyoxyethylene cetyl ether phosphate, polyoxyethylene stearyl ether phosphate, polyoxyethylene caster ether phosphate, and combinations thereof It may be an alkali metal salt or an alkaline earth metal salt of a branched alkyl oxy polyoxy ethylene phosphoric acid containing a material selected from the group.

More specifically, as an emulsifier, α-tridecyl-ω-hydroxypoly(oxy-1,2-ethanediyl), sodium salt of α-tridecyl-ω-hydroxypoly(oxy-1,2-ethanediyl), phosphate, sodium salt), α-(Nonylphenyl)-ω-hydroxypoly(oxy-1,2-ethanediyl)phosphate sodium salt (α-(Nonylphenyl)-ω-hydroxypoly(oxy-1,2-ethanediyl)phosphate , sodium salt), α-Dodecyl-ω-hydroxypoly(oxy-1,2-ethanediyl) phosphate sodium salt (α-Dodecyl-ω-hydroxypoly(oxy-1,2-ethanediyl) phosphate , sodium salt ), poly(oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy-, mono-C13-15-alkyl ether, succinate sodium salt (Poly( oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy-, mono-C13-15-alkyl ethers, succinates, sodium salt) are preferably used alone or together.

When the above-mentioned emulsifier is used, there is an advantage in that the transparency and heat resistance of the polymer resin are excellent after emulsion polymerization, and there is an effect of reducing the stickiness of the resin powder during powdering.

The emulsifier containing such a phosphoric acid ester salt may be used alone, or two or more types may be mixed and used, and it is also possible to use other compounds in a compound containing a phosphoric acid ester salt, and two types of phosphoric acid ester salts In the case of mixing the above, a mixture of monoalkyl ester and dialkyl ester may be used.

In the polymerization step, the additive material may be mixed for polymerization of the monomer. The additive includes a catalyst, and may include a molecular weight modifier and a chelating agent.

The catalyst promotes the emulsion polymerization reaction and is included to reduce the concentration of unreacted monomers during emulsion polymerization. As the catalyst material, a commonly used catalyst material for emulsion polymerization may be used, for example, Rongalite (formaldehyde sulfoxylate sodium salt), ascorbic acid or potassium metabisulfite may be used. It is preferable to increase efficiency and to help stabilize the emulsion when a phosphoric acid ester-based emulsifier is used.

A compound such as EDTA is preferably used as the chelating agent, and interfacial stabilization of the dispersed phase can be improved together with a phosphoric acid ester-based emulsifier.

This polymerization step is preferably carried out by adding the emulsion while stirring by first adding the catalyst or additive to the reaction vessel. By injecting the emulsion in which the monomer and the initiator are mixed into the reaction vessel in which the catalyst is stirred, the contact area between the catalyst and the emulsion is wide and a uniform reaction can occur, so that the length of the polymer and the particle size of the dispersed phase are uniformly obtained.

The catalyst or additive is preferably added after the initiator is blended into the monomer mixture. When the catalyst is added after the initiator is uniformly mixed with the monomer mixture, the reaction between the initiator radical and the monomer dissolved in the dispersed aqueous solution is uniformly performed, and the reaction time can be easily controlled.

When the catalyst is added before or simultaneously with the initiator, it is difficult to achieve a uniform reaction in the reaction vessel, so there may be problems in that the particle size of the dispersed phase becomes uniform or the molecular weight deviation of the polymer becomes large.

During emulsion polymerization, the emulsifier forms a dispersed phase in the form of droplets or micelles dispersed in an aqueous solution as a dispersion medium. The particle size of the dispersed phase may vary depending on the type of emulsifier, the concentration of the emulsifier, and the degree of stirring, but is preferably 1 μm or less, and more preferably 0.5 μm or less, 0.2 μm or less.

The monomer has a small molecular weight and may be dissolved together with an initiator or radical dissolved in an aqueous solution as a dispersion medium, and is polymerized in an aqueous solution to become an oligomer, trapped in the dispersed phase, polymerized with other oligomers, included in the dispersed phase, or stabilized by a systemic emulsifier.

Specifically, the place where the emulsion polymerization can occur may be inside the monomer droplet, the interface between the monomer droplet and the aqueous solution as a dispersion medium, the aqueous solution phase, or the inside of the dispersed phase containing the polymer.

The smaller the particle size of the dispersed phase, the greater the surface area where emulsion polymerization takes place, and thus the reaction efficiency is high and the reaction rate is increased, thereby increasing the molecular weight of the polymer.

In a preferred embodiment of the present invention, it is possible to polymerize the core 1 and at least one shell formed on the core 1 using an emulsion polymerization method in the polymerization step.

The polymerization step may more specifically include a core polymerization step and a shell polymerization step, and the shell polymerization step may be performed continuously at least once or more.

The core polymerization step is the first emulsion polymerization of an acrylic monomer mixture including an acrylic monomer using an emulsifier. At this time, the acrylic monomer mixture input to prepare the core 1 may be defined as a first monomer mixture. .

The core 1 obtained by emulsion polymerization in a reaction vessel in which the first monomer mixture, initiator and catalyst are present is dispersed in an emulsion phase, and a second monomer mixture, which is an acrylic monomer mixture having a composition different from that of the first monomer mixture, is added thereto. A core-shell polymer having a core-shell structure can be obtained by adding emulsion polymerization and carrying out a shell polymerization step of preparing a shell structure on the surface of the core 1 .

In the shell polymerization step, additional acrylic monomer polymerization proceeds in an emulsion in which the polymerized core 1 is dispersed in a dispersed phase, and polymers with increased molecular weight are caught on or crosslinked on the surface of the core 1, and on the surface of the core 1 can grow

The shell polymerization step may be performed only once, and may be repeated two or more times. When repeated two or more times, the mixture included for the shell polymerization has a composition different from that of the first monomer mixture and the second monomer mixture. It is preferable to use an acryl-based monomer mixture, which may be defined as a second monomer mixture and a third monomer mixture in order, respectively, or may be expressed as an n-th monomer mixture. (n is a natural number greater than or equal to 2)

In this case, the nth monomer mixture is used to synthesize the (n-1)th shell, and n may be 2 to 10, preferably 2 to 4.

When n is too large, the synthesis time becomes difficult, and there may be a problem in that the shape of the resin powder is not uniform.

When the shell formed on the core 1 has two or more layers, it can be defined as the first shell 2, the second shell 3, the n-th shell, etc. in order from the inside to the outside, and the first shell 2 Silver is a shell layer provided on the surface of the core 1, and the shell formed on the first shell 2 may be sequentially provided with the second shell 3, the n-th shell, and the like.

Here, the second shell 3 is preferably synthesized from a monomer mixture having a different composition from the monomer mixture used for polymerization of the first shell 2, and the nth shell is used for polymerization of the (n-1)th shell. It is preferable to synthesize from a monomer mixture having a composition different from the monomer mixture, and more preferably, the n-th shell is different from the monomer mixture used for polymerization of the core (1), the first shell (2) to the (n-1) shell. It is preferably synthesized from a mixture of monomers having a composition.

Specifically, an emulsion polymerized from the (n+1)th monomer mixture on the core-shell polymer by adding a (n+1)th monomer mixture having a composition different from that of the nth monomer mixture with respect to a natural number n of 2 or more The step of synthesizing the n-th shell including the polymer may be included in the shell polymerization step.

Since the resin powder has a core-shell structure or a multi-layered shell structure polymerized with a monomer mixture having a composition different from the adjacent core 1 or shell, the elasticity of the resin powder and the molded article formed by molding the resin powder can be improved, preferably For example, a molded body used as a material for impact reinforcement and a resin powder for manufacturing the same can be prepared.

On the other hand, in the resin powder in which two or more shells are formed, the ratio of the monomers contained in each shell may have a specific relationship, for example, from the inner first shell 2 to the outer nth shell included in the monomer mixture. It is desirable to increase or decrease the content of a particular monomer.

In one embodiment of the present invention, the second to fourth monomer mixtures for forming each shell layer in the first shell 2 and the second shell 3 include MMA and BA monomers, and MMA polymerized in each shell layer and The content ratio of BA is made different from each other, and specifically, it is preferable that the ratio of MMA to BA (part by weight of MMA/part by weight of BA) in the second shell 3 is greater than or equal to that of the first shell 2 .

Furthermore, in the case of a resin powder including three shells, the ratio of MMA to BA (parts by weight of MMA/parts by weight of BA) contained in the second monomer mixture constituting the first shell 2 is X1, and the second When the ratio of MMA and BA included in the monomer mixture constituting the shell 3 is X2, and the ratio of MMA and BA included in the monomer mixture constituting the third shell 4 is X3, the relationship between X3 ≥ X2 ≥ X1 A monomer mixture satisfying the above may be used to prepare a multi-layered resin powder.

As X1 to X3 satisfy the above relationship in the multi-layer structure, the prepared resin powder has excellent elastic properties and at the same time it cannot be destroyed or plastically deformed from external force or impact, so it can have properties suitable for use as a material for impact reinforcement. there is.

The shell polymerization step is preferably performed in a batch or semi-batch method continuously performed in the reaction vessel in which the core 1 polymerization is performed after the core polymerization step, and is added during emulsion polymerization of the core 1 Since the used monomer and initiator are consumed in the emulsion polymerization step of the core 1, a new monomer mixture and initiator must be added in the shell polymerization step.

Since the catalyst does not disappear or lose activity while participating in the reaction, it is preferable not to be additionally added in the shell polymerization step.

That is, although the catalyst is added in the core polymerization step, it is possible to carry out the emulsion polymerization without being added in the subsequent shell polymerization step. Due to these characteristics, the polymerization proceeds by the monomer mixture and the initiator added to the reaction vessel in a state in which the catalyst is uniformly dispersed, so that a uniform emulsion polymerization can be obtained in the shell polymerization step, and the catalyst can be reused. It has the advantages of improved economic feasibility and no separate catalyst separation process.

On the other hand, before recovering the polymerized polymer as a resin powder, if necessary, a filtration step of treating the polymer as a product using a filtration device may be further included.

The above filtration step may be, for example, a step for the purpose of removing foreign substances generated during polymerization or foreign substances mixed in from the outside during the removal polymerization raw material or during polymerization from the emulsion polymer (acrylic polymer), and It can be preferably used for molding a resin molded body having excellent properties by using the powder.

More specifically, particulate silica or ultra-fine silica contained in an emulsifier, etc. may be included as an impurity. .

As a filtration device, a susnet, a cartridge filter, a micro filter, a decanter, a centrifuge, etc. can be used.

A method of recovering the acrylic emulsion polymer prepared in the polymerization step of performing the emulsion polymerization process is not particularly limited, but a method of coagulating a core-shell polymer (acrylic polymer) having a core-shell structure in contact with a coagulant solution may be used. It can be obtained by coagulating the emulsion-polymerized polymer in the coagulation step.

The resin powder manufacturing method of the present invention includes a coagulation step of contacting the core-shell polymer obtained in the polymerization step with a coagulant to pulverize the coagulated emulsion polymer, and in the coagulation step, the acrylic polymer obtained through polymerization and coagulation reaction It can be obtained in a form that is easy to obtain as a product by coagulating the polymer material of

The coagulant used in the coagulation step preferably includes, for example, phosphoric acid and a compound represented by the general formulas 1 and 2.

In more detail, as the coagulant preferably used in the coagulation step, inorganic salts, inorganic acids, organic acids, organic acid salts or mixtures thereof may be used, for example, an aqueous solution containing a water-soluble salt of an alkali metal or alkaline earth metal is used. can be used

Here, the inorganic salts include, for example, calcium acetate, calcium chloride, sodium chloride, potassium chloride, lithium chloride, sodium bromide, potassium bromide, lithium bromide, potassium iodide, lithium iodide, potassium sulfate, ammonium sulfate, sodium sulfate, ammonium chloride, sodium nitrate. , potassium nitrate, calcium chloride, magnesium sulfate, zinc sulfate, copper sulfate, cadmium sulfate, barium chloride, ferrous chloride, magnesium chloride, ferric chloride, ferric sulfate, potassium aluminum sulfate alum or iron alum can be used.

Hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc. may be used as organic acids, acetic acid, formic acid, etc. may be used as organic acids, and sodium acetate, sodium formate, calcium formate, etc. may be used as an organic acid salt.

Among these, particularly preferably, in the case of a resin powder obtained from emulsion polymerization of an acrylic monomer, calcium acetate is preferably used as a coagulant in terms of the temperature resistance of the resin molded body molded with the resin powder and the low water content of the recovered powder. It is also good to use a mixture of two or more types of compounds including calcium acetate.

The coagulant is generally added in the form of an aqueous solution, for example, the concentration of the aqueous calcium acetate solution is preferably 1% by mass or more. In addition, the concentration of the coagulant, for example, an aqueous solution of calcium acetate, has a small amount of the coagulant remaining in the recovered polymer. It is preferably used in an amount of 1 to 20% by weight, preferably 2 to 15% by weight.

When the concentration of the coagulant exceeds the corresponding range, there is a problem in that calcium acetate is precipitated by saturation at 10 ° C. or less.

The method of bringing the core-shell polymer into contact with the coagulant is not particularly limited, but for example, a method of continuously adding the core-shell polymer thereto while stirring the knife coagulant and maintaining it for a certain period of time and a constant ratio of the coagulant and the core-shell polymer and a method of continuously withdrawing a mixture containing a solidified core-shell polymer and water from the vessel by continuously pouring it into a vessel equipped with a furnace stirrer and contacting it.

The amount of the coagulant used in the coagulation step is not particularly limited, but is preferably 10 to 500 parts by weight based on 100 parts by weight of the core-shell polymer, and preferably 50 to 300 parts by weight based on 100 parts by weight of the core-shell polymer. desirable.

The temperature conditions of the coagulation step are not particularly limited, but it is preferably 30 ° C. to 100 ° C., and the contact time in the coagulation step is not particularly limited.

In addition, the method for preparing the resin powder from the emulsion polymer may include continuous coagulation and precipitation. The resin powder obtained through the polymerization and solidification steps preferably includes a core 1 provided at the center of the powder, and a shell (or shell layer) provided on the core 1, wherein the shell (or shell layer) ) is preferably included in at least one on the core 1 to have a single-layer structure or a multi-layer structure.

The particle diameter of the resin powder is not limited, but may be, for example, 0.1 to 300 μm.

On the other hand, when a salt containing calcium is used as the coagulant, a large amount of calcium phosphate is generated by the reaction of the coagulant and the emulsifier in the coagulation step. Due to the calcium phosphate mixed therein, the appearance of the obtained resin molded body deteriorates, or the screen mesh that removes foreign substances in the melt extrusion during molding is clogged in a short time, thereby reducing the productivity of melt extrusion.

Accordingly, the resin powder manufacturing method of the present invention includes a step of removing impurities after the solidification step, thereby significantly lowering the impurity content contained in the product during molding of the resin powder and improving the physical properties of the product.

The impurity removal step is a step of dissociating and removing insoluble salts or foreign substances that are synthesized in the coagulation step and contained together with the resin powder having a structure including the core 1 and the shell.

The impurity removal step may be a step made by treating the coagulated resin powder with a dissociating agent capable of dissociating insoluble salts or foreign substances contained in the product after the coagulation step.

For example, in the impurity removal step, an inorganic acid may be used as a dissociating agent, and the dissociating agent may be washing water or aqueous solution having a pH of 7 or less, preferably an acidic aqueous solution having a pH of 2 to 6, more preferably a pH It is preferable that is 2 to 4.

If the pH of the aqueous solution of the dissociating agent exceeds 4, the dissociation effect of the foreign material is lowered, and the removal of the foreign material is not performed sufficiently, or the particle size of the remaining foreign material is increased, so that there may be a problem of poor quality of the latex product finally obtained.

In addition, in the impurity removal step, the acrylic polymer powder is washed, so that the insoluble salt generated in the polymerization and coagulation step reacts under acid conditions to form a molten salt, and the molten salt is easily washed with a washing solution that is an aqueous solution of a dissociating agent. Since it can be removed, it is possible to produce a resin powder with a low content of foreign substances and excellent appearance.

As the above-mentioned dissociating agent, an inorganic acid such as nitric acid or hydrochloric acid may be used, and an aqueous dissociating agent solution prepared by adjusting the pH to 7 or less by adding an inorganic acid to water is preferably used.

Although the temperature and pressure for performing the impurity removal step are not particularly limited, it is preferably 30°C or higher, and 100°C or lower.

More preferably, the temperature is preferably 40 to 80 °C, preferably 45 to 75 °C. If the temperature is out of the range, the reaction rate is not constant, so it is difficult to obtain a polymer with uniform physical properties, and there may be a problem in that the stability of the emulsion is lowered.

The time period for bringing the aqueous solution of the dissociating agent into contact with the resin powder is not particularly limited.

On the other hand, when only washing water having a neutral or near-neutral pH is simply used as in the embodiment, it is economically and technically difficult to remove foreign substances satisfactorily regardless of the washing time, so the removal of impurities may be inefficient.

In the impurity removal step, as in a preferred embodiment of the present invention, excellent impurity removal results can be obtained only with an aqueous solution of a dissociating agent having a pH of 4 or less under normal temperature and pressure conditions.

In addition, since the resin powder has a multi-layer structure including a core and a shell structure, dissociation of the resin powder does not occur even when an aqueous solution of a dissociating agent is used at a low pH, and excellent physical properties can be maintained. Contamination or reaction can be minimized.

1 is a view showing a cross-sectional structure of a resin powder having a multi-layered core-shell form according to an embodiment of the present invention, wherein a first shell 2, a second shell 3 and a third shell are placed on the inner core. (4) is provided.

The resin powder having a core-shell structure prepared through the method of the present invention has an average particle diameter of 1 μm or less, preferably 0.6 μm or less, and preferably 0.4 μm or less, 0.2 μm or less, and 0.15 μm or less.

In addition, when two or more shells are formed, it is preferable that the shell has a thinner thickness as the shell is later polymerized and formed outside. In the initial stage of the shell polymerization step, the small cores are widely dispersed so that the shell can be formed quickly on the surface, so it is better to form a thick shell. When the thickness is thin, the physical properties of the resin can be uniformly obtained while reducing the overall particle size deviation of the resin powder.

If the average particle diameter of the resin powder is larger than the corresponding range, the particle shape may not be uniform, the variation in particle diameter of the obtained resin powder may increase, and the particle size and difference of impurities decrease, making separation difficult. there may be

Hereinafter, a method of molding a molded article or manufacturing a product by molding the resin powder prepared by the above-described method will be described as an example.

The resin powder is generally molded into various resin molded products by adding a compounding agent as necessary, such as extrusion, injection molding, vacuum molding, blow molding, and compression molding.

Examples of the compounding agent include stabilizers, lubricants, processing aids, plasticizers, shock absorbers, fillers, antibacterial agents, mold inhibitors, foaming agents, mold release agents, antistatic agents, colorants, matting agents, ultraviolet absorbers, and thermoplastic polymers. In particular, it is preferable to add a thermoplastic polymer in order to improve the heat resistance of the resin molded body and its scratch resistance. Examples of the thermoplastic polymer used for this purpose include methyl methacrylate and polycarbonate. .

As a method of adding a compounding agent, a method of supplying a powder made of an acrylic polymer and an additive together to a molding machine that can obtain a resin molded body, and a method of kneading and mixing a raw material mixture with a compounding agent added to an acrylic polymer before molding in various kneaders in advance The placement method may be used. Here, as the kneader, any one of a general single screw extruder, a twin screw extruder, a Banbury mixer, a roll kneader, and the like may be used.

When the powder is an acrylic resin, particularly, an acrylic multilayer structure resin powder, when the acrylic resin is molded into a resin film, its industrial utility value increases. The uses of acrylic resin film are: agricultural plastic house, marking film, poster, wallpaper, foam sheet, outdoor salt rain leather, PVC steel sheet roof and siding materials, etc. , flooring, corrugated boards, makeup columns, lighting, and products that use water such as bathrooms and kitchens. Others include heat insulation films, polarizing film protective films used in polarizing plates such as liquid crystal displays, and retardation films used in retardation plates for viewing angle compensation and retardation compensation.

As a method of forming into a film, a known solution flow extension method, a T-die method, and a melt extrusion method such as an inflation method are mentioned. Among them, the T-die method is most preferable in terms of economy.

The acrylic resin film may be used for various uses as it is, or may be appropriately laminated on a substrate for use. When a transparent acrylic resin film is laminated on a substrate, it can be used as an alternative to clear painting and can preserve the color tone of the substrate. In this way, the acrylic resin film is superior to the polyvinyl chloride film or the polyester film in terms of transparency, depth and luxury compared to polyvinyl chloride film or polyester film for the purpose of making use of the color tone of the substrate.

The type or material of the base material for laminating the acrylic resin film is not limited, and examples thereof include molding woodworking products made of various resins and metals. When the base material is a resin, a thermoplastic resin capable of melt adhesion of an acrylic resin film is preferable, and ABS resin, AS resin, polystyrene resin, polycarbonate resin, vinyl chloride resin, acrylic resin, polyester-based resin, or a resin containing it as a main component is preferable. Among them, ABS resins, AS resins, polycarbonate resins, vinyl chloride resins, or resins containing these resins as a main component are preferable from the viewpoint of adhesiveness. In addition, in the case of a substrate made of a resin that is difficult to melt and adhere, such as polyolefin resin, an acrylic resin film can be laminated after installing an appropriate adhesive layer.

When the substrate has a two-dimensional shape and the substrate is a material that can be thermally fused, the substrate and the acrylic resin film can be laminated by a known method such as thermal lamination. It is also possible to use an adhesive on a substrate made of a material that is difficult to heat-seal, or to adhesively process or laminate a cross section of an acrylic resin film.

When the base material has a three-dimensional shape, an insert molding method in which an acrylic resin film processed in a predetermined shape is inserted into an injection mold, and an in-mold molding method in which injection molding is performed after vacuum molding in the mold. A base material and an acrylic resin film can be laminated|stacked.

Among them, in the in-mold molding method, the acrylic resin film is vacuum-molded to form a three-dimensional shape, and then the resin, the raw material of the substrate, is poured into the molded product by injection molding to integrate it. desirable. In addition, molding and injection molding of an acrylic resin film can be performed in one process, and it is preferable from the viewpoint of excellent workability and economical efficiency.

When the acrylic resin film is laminated on the substrate for at least one purpose of protecting the substrate, the acrylic resin film is preferably added with a UV absorber to impart weather resistance. Although it does not specifically limit as a kind of ultraviolet absorber, From the point of improving the heat resistance and processability of a resin, an amine type and a phenol type are preferable.

In addition, the surface of the acrylic resin film may be subjected to surface treatment such as coating for imparting various functions, if necessary. Surface treatment for imparting functions includes printing treatment such as silk printing and inkjet printing, metal deposition and sputtering wet plating treatment to impart metallic tone or anti-reflection, surface hardening treatment to improve surface hardness, water repellent treatment to prevent contamination, or A photocatalyst layer formation treatment, an antistatic treatment for the purpose of preventing dust adhesion or electromagnetic wave blocking, a reflection preventing layer formation, an anti-glare treatment, a matting treatment, and the like are mentioned.

As described above, an emulsion polymerization emulsion polymerization process is performed on the monomer component using an emulsifier containing phosphoric acid and a phosphoric acid ester salt represented by Formula 1 or 2, and the obtained acrylic polymer is contacted with an aqueous calcium salt solution to coagulate, in the coagulation step If the generated foreign material such as calcium phosphate is washed with water as a dissociating agent solution having a pH of 7 or less in the subsequent water washing process, the foreign material can be minimized. Therefore, if the powder made of the recovered polymer is molded after the water washing process, a resin molded body in good condition is obtained without clogging the screen mesh for removing foreign substances in a short time during melt extrusion during molding.

That is, according to the emulsion polymerization process using such an emulsifier, it is possible to provide an acrylic polymer containing a polymer capable of forming a molded article having an excellent appearance with good productivity.

In addition, in particular, the acrylic polymer prepared by the above method is an emulsion polymerization latex polymer, and when the emulsion polymerization latex polymer includes an acrylic resin such as an acrylic multilayer structure polymer, the emulsion polymerization latex polymer is a core-shell structure polymer By recovering the powder and molding it, an acrylic resin molded article such as an acrylic resin film excellent in weather resistance, transparency, printability, and hot water whitening resistance can be produced.

Hereinafter, the content of the present invention will be described in detail by way of Examples.

(Example)

Example 1 - Preparation of multi-layer structure resin powder

After putting 9 parts by weight of ion-exchanged water into a container with a stirrer, 0.35 parts by weight of methyl methacrylate (MMA), 4 parts by weight of butyl acrylate (BA), 0.2 parts by weight of ethylene glycol dimethacrylate (EGMA), aryl methacrylic A mixture of a first monomer consisting of 0.05 parts by weight of rate (AMA) and 0.025 parts by weight of t-butyl hydroperoxide (t-BH) was added and mixed with stirring.

containing α-tridecyl-ω-hydroxypoly(oxy-1,2-ethanediyl)phosphate sodium salt (α-Tridecyl-ω-hydroxypoly(oxy-1,2-ethanediyl), phosphate, sodium salt) 1.5 parts by weight of the emulsifier was put into the container while stirring, and stirring was continued for 20 minutes to prepare an emulsion. The average particle diameter of the dispersed phase in the obtained emulsion was 0.2 micrometer.

Thereafter, 200 parts by weight of ion-exchanged water was added to a polymerization vessel with a cooler, and the temperature was raised to 70° C., 0.20 parts by weight of Longarite (CAS NO: 149-44-0), 0.0001 parts by weight of iron sulfate to 5 parts by weight of ion-exchanged water , the mixture prepared by adding 0.0003 parts by weight of EDTA was introduced.

Then, the emulsion prepared above was added dropwise to the polymerization vessel for 8 minutes while stirring under nitrogen, and then the reaction was continued for 15 minutes to complete the polymerization of the core from the first monomer mixture.

Thereafter, a second monomer mixture consisting of 1 part by weight of MMA, 23 parts by weight of BA, 1.0 part by weight of EGMA, and 0.25 parts by weight of AMA was added to the polymerization vessel together with 0.012 parts by weight of t-butyl hydroperoxide (t-BH) for 90 minutes. Then, the reaction was continued for 60 minutes to form the polymer polymerized from the second monomer mixture as the first shell 2 on the core.

Then, a third monomer mixture containing 5 parts by weight of MMA, 5 parts by weight of BA, 0.1 parts by weight of AMA and 0.01 parts by weight of t-butyl hydroperoxide (t-BH) was added dropwise to the polymerization vessel for 45 minutes, followed by reaction for 60 minutes. Subsequently, the second shell 3 was formed on the first shell 2 .

Then, a fourth monomer mixture consisting of 48 parts by weight of MMA, 5.2 parts by weight of BA, 0.2 parts by weight of n-dodecyl mercaptan (n-dM) and 0.1 parts by weight of t-butyl hydroperoxide (t-BH) was placed in a polymerization vessel for 140 minutes. After dripping, reaction was continued for 60 minutes, the 3rd shell 4 was formed on the 2nd shell 3, and the polymer resin powder which has a multilayer structure was obtained.

Then, the polymerized polymer was coagulated by adding an emulsion-polymerized emulsion including a core-shell structure to a stirring vessel while stirring an aqueous solution containing calcium acetate in an amount of 5% by weight.

It was confirmed that when the content of the MMA component among the monomer components was increased, the polymer became hard and the elasticity was lowered. When the content of BA was increased, it was confirmed that the polymer became soft and the elasticity was improved.

At this time, the resin powder measured after polymerization had a weight average particle diameter of 0.15 μm when measured by a dynamic light scattering method using a light scattering photometer, and was confirmed to be in the range of 0.1 to 70 μm.

Examples 2 to 8 - Removal of foreign substances from the resin powder

Example 2

As an emulsifier in Example 1, α-(Nonylphenyl)-ω-hydroxypoly(oxy-1,2-ethanediyl)phosphate sodium salt (α-(Nonylphenyl)-ω-hydroxypoly(oxy-1,2-ethanediyl) ) phosphate , sodium salt) was washed with a nitric acid aqueous solution having a pH of 6, followed by dehydration and drying to obtain a resin powder product.

Example 3

As an emulsifier in Example 2, α-Dodecyl-ω-hydroxypoly(oxy-1,2-ethanediyl) phosphate, sodium salt) and poly(oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy-, mono-C13-15-alkyl ether, succinate sodium salt (Poly(oxy-1, 2-ethanediyl), .alpha.-hydro-.omega.-hydroxy-, mono-C13-15-alkyl ethers, succinates, sodium salt) were used, except that an aqueous nitric acid solution having a pH of 5 was used as washing water. Then, a resin powder product was obtained in the same manner as in Example 2.

Examples 4 to 6

A resin powder product was obtained in the same manner as in Example 2, except that in Example 1, an aqueous solution of nitric acid having a pH of 4, 3, or 2 was used as an aqueous dissociating agent.

Examples 7 and 8

A resin powder product was obtained in the same manner as in Example 4, except that in Example 4, aqueous solutions of a dissociating agent having a pH of 4 were used as aqueous solutions of hydrochloric acid and sulfuric acid, respectively, instead of aqueous solutions of nitric acid.

(Comparative example)

Comparative Example 1

The multi-layered resin powder obtained in Example 1 was washed with an aqueous solution having a pH of 7, followed by dehydration and drying to obtain a resin powder product.

Comparative Examples 2-3

A resin powder product was obtained in the same manner as in Comparative Example 1, except that in Comparative Example 1, an aqueous solution of ammonium acetate having a pH of 6.7 and 7.39 was used as the aqueous solution of the dissociating agent.

Comparative Example 4

A resin powder product was obtained in the same manner as in Example 1, except that the first to third shells were formed using a monomer mixture having the same monomer composition as the first monomer mixture used for preparing the core.

Comparative Example 5

A resin powder product was obtained in the same manner as in Example 1, except that the second to third shells were formed using a monomer mixture having the same monomer composition as the monomer mixture used for preparing the first shell.

(Experimental example)

Experimental Example 1 - Analysis of foreign substances in resin powder

The multilayer structure resin powder of Example 2 is dispersed in acetone at a concentration of 1 to 5% by weight to prepare a dispersion, and the foreign substances present in the dispersion are repeatedly used to obtain a precipitate by using a precipitation method by a difference in specific gravity to obtain a component by FT-IR was analyzed through

As a result, it was confirmed that the component of the precipitate was calcium phosphate.

Experimental Example 2 - Test for the content of foreign substances in the resin molded body

After molding using the resin powder of Examples 1 to 8 and Comparative Examples 1 to 3 to produce a transparent plate sample molded body having a thickness of 3 mm, the sample was included in an area having a width of 5 cm and a length of 5 cm using a spectroscopic microscope. The number and approximate size of the salt or foreign particles were measured using a polarized light microscope or Raman spectrometer.

sample washing liquid ingredients wash solution pH Resin powder average particle size (㎛) number of foreign objects
(pcs/cm ² ) Average particle diameter of foreign particles (㎛) Example 2 nitric acid solution 6 0.15 200 0.3-200 Example 3 nitric acid solution 5 0.15 150 0.3-200 Example 4 nitric acid solution 4 0.19 10 0.3-10 Example 5 nitric acid solution 3 0.18 7 0.3-2 Example 6 nitric acid solution 2 0.15 6 0.3-1 Example 7 hydrochloric acid solution 4 0.20 12 0.3-10 Example 8 sulfuric acid solution 4 0.20 11 0.3-10 Comparative Example 1 acetic acid solution 4 0.21 32 0.3-10 Comparative Example 2 Ammonium acetate aqueous solution 6.7 0.24 300 0.3-200 Comparative Example 3 Ammonium Acetate Aqueous Solution 7.39 0.26 350 0.3-200

In Examples in which nitric acid, hydrochloric acid, or sulfuric acid aqueous solution was used as the dissociating agent aqueous solution, a large number of foreign substances was observed when the pH was 5 and 6, and it was confirmed that the average size of the foreign substances particles was also large.

As the pH of the aqueous solution of the dissociating agent decreased, the number and average particle diameter of foreign substances decreased, so that the appearance characteristics were improved, and it was confirmed that the dissociation of the impurities proceeded well.

In the comparative example using acetic acid and ammonium acetate, the number of foreign substances increased compared to the example, and the average particle diameter of the foreign substances also increased.

Experimental Example 3 - Measurement of physical properties of resin powder

Using the resin powders of Examples 1 to 3 and Comparative Examples 4 and 5, elasticity and hardness properties were measured and shown in Table 4. Elastic properties and hardness properties were expressed in four stages: ****: very good, ***: good, **: normal and *: bad). In the case of elastic properties, the better the shock absorption and restoration properties, the better, and the higher the hardness, the better.

elastic properties hardness characteristics Example 1 **** *** Example 2 **** *** Example 3 **** *** Comparative Example 4 **** * Comparative Example 5 ** ***

As in the Examples, when a resin powder having a core-shell structure with different contents of BA and MMA was used, the elastic properties and hardness properties were excellent or good, but as in Comparative Examples, a monomer mixture composition with a high BA content was used for core and It was found that when the same was used for the shell, the hardness decreased, and when the same composition of the monomer mixture with a low BA content was used for the shell, the elastic properties deteriorated.

Features, structures, effects, etc. exemplified in each of the above-described embodiments may be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

1: core
2: first shell
3: second shell
4: third shell

Claims (13)

a core polymerization step of emulsifying a first monomer mixture including an acrylic monomer with a phosphoric acid-based emulsifier and then emulsifying the core dispersed in the emulsion phase by emulsion polymerization in a reaction vessel;
a shell polymerization step of synthesizing a first shell including an emulsion polymer polymerized from the second monomer mixture on the core by introducing a second monomer mixture having a composition different from that of the first monomer mixture into the reaction vessel;
a coagulation step of coagulating the core-shell polymer polymerized in the shell polymerization step by contacting it with a coagulant containing a water-soluble salt of an alkali metal or alkaline earth metal; and
an impurity removal step of removing the insoluble salt produced by the reaction of the phosphoric acid-based emulsifier and the coagulant with an aqueous acidic dissociating agent; A resin powder manufacturing method comprising a.
The method of claim 1,
The shell polymerization step is
With respect to a natural number n of 2 or more, an emulsion polymer polymerized from the (n+1)th monomer mixture on the core-shell polymer by adding a (n+1)th monomer mixture having a composition different from the nth monomer mixture A method for producing a resin powder comprising the step of synthesizing an n-th shell.
3. The method of claim 2,
The first monomer mixture to the (n+1)th monomer mixture are acrylic monomers such as methyl methacrylate (MMA), butyl acrylate (BA), ethylene glycol dimethacrylate (EGMA) and aryl methacrylate (AMA). ) A method for producing a resin powder comprising at least one selected from the group consisting of.
4. The method of claim 3,
The second monomer mixture to the (n+1)th monomer mixture include the methyl methacrylate (MMA) and the butyl acrylate (BA).
5. The method of claim 4,
The weight ratio of methyl methacrylate and butyl acrylate (MMA/BA) included in the (n+1)-th monomer mixture is the weight ratio of methyl methacrylate and butyl acrylate in the n-th monomer mixture (MMA/BA) ) larger than the resin powder manufacturing method.
6. The method of claim 5,
The acidic dissociating agent aqueous solution has a pH of 2 to 4 resin powder manufacturing method.
7. The method of claim 6,
The acidic dissociating agent aqueous solution is an inorganic acid aqueous solution.
8. The method of claim 7,
The coagulant is an aqueous solution containing 1 to 20% by weight of the water-soluble salt of the alkali metal or alkaline earth metal, the resin powder manufacturing method.
9. The method of claim 8,
In the core polymerization step, a solution containing a catalyst or an additive is stirred in the reaction vessel, and the first monomer mixture is introduced into the reaction vessel.
10. The method of claim 9,
The phosphoric acid-based emulsifier is a resin powder manufacturing method comprising a phosphoric acid ester salt represented by the following general formula 1 or the following general formula 2.

(General formula 1)

(General formula 2)

(In Formulas 1 and 2, R is a linear or branched alkyl group having 10 to 18 carbon atoms, M is an alkali metal or alkaline earth metal element, and n is an integer of 1 to 20 that is the same or different from each other.)
As a resin powder prepared by the method of any one of claims 1 to 10,
A resin powder having an average particle diameter of 0.3 to 200 μm of impurities contained in the resin powder.
12. The method of claim 11,
The resin powder is a core; and
Including; at least one shell provided on the core;
A resin powder having a multi-layer structure in which the composition of the monomers included in the core and the polymer constituting the resin are different from each other.
A resin molded article produced by adding a compounding agent to the resin powder of claim 12 and molding by any one or more methods of an extrusion method, an injection molding method, a vacuum molding method, a blow molding method, or a compression molding method.

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