JP7009156B2 - Manufacturing method of thermoplastic resin powder - Google Patents

Description

The present invention relates to a method for producing a thermoplastic resin powder.

In order to recover the thermoplastic resin from the dispersion obtained by emulsion polymerization or the like, generally, the thermoplastic resin particles are aggregated to a size of several tens to several hundreds of μm and recovered as powder through the steps of dehydration and drying. The method is taken. The freeze-thaw method is known as one of the methods for aggregating the thermoplastic resin particles contained in the dispersion (see, for example, Patent Document 1). In this method, the dispersion liquid containing the thermoplastic resin particles is thawed after freezing, whereby a sol containing agglomerates of the thermoplastic resin particles is formed.

Japanese Unexamined Patent Publication No. 2000-327712

However, in the above freeze-thaw method, agglomerates of thermoplastic resin particles (particularly those in which such agglomerates are stuck) adhere to the dehydrator or piping during or after dehydration, and are stable for a long period of time. It may be difficult to continuously produce powder.

Therefore, an object of the present invention is to provide a method for producing a thermoplastic resin powder capable of stably and continuously producing a powder for a long period of time.

As a result of diligent studies by the present inventors in order to achieve the above object, if inorganic particles are added before dehydration, adhesion of agglomerates to the dehydrator and piping is suppressed and stable and continuous for a long period of time. The present invention was completed by further studying based on the finding that it is possible to produce a powder.

That is, the present invention relates to the following [1] to [9].
[1] A step (1) of freezing the dispersion liquid containing the thermoplastic resin particles, and a step (2) of melting the frozen dispersion liquid to obtain a slurry (a) containing an aggregate of the thermoplastic resin particles. The step (3) of mixing the inorganic particles with at least one selected from the group consisting of the dispersion liquid after freezing and the slurry (a), and dehydrating the slurry (b) containing the obtained aggregates and inorganic particles. A method for producing a thermoplastic resin powder, which comprises the step (4).
[2] The production method according to [1], wherein the dispersion liquid containing the thermoplastic resin particles is obtained by emulsion polymerization.
[3] In [1] or [2], the thermoplastic resin particles are acrylic multilayer structure polymer particles having at least an acrylic soft polymer layer and an outer acrylic hard polymer layer. The manufacturing method described.
[4] The acrylic soft polymer has a unit of acrylic acid ester of 50 to 95% by mass and a unit of another monofunctional monomer copolymerizable with the acrylic acid ester of 0 to 49.99% by mass. The production method according to [3], which comprises 0.01 to 10% by mass of the unit of the polyfunctional monomer.
[5] The acrylic hard polymer contains 40 to 99% by mass of a unit of methacrylic acid ester and 1 to 60% by mass of another monomer copolymerizable with the methacrylic acid ester. [3] Alternatively, the manufacturing method according to [4].
[6] The production method according to any one of [1] to [5], wherein the thermoplastic resin particles have an average particle diameter of 150 nm or less.
[7] The method according to any one of [1] to [6], wherein the steps (2) and (3) are performed by mixing the frozen dispersion and the dispersion containing inorganic particles. Production method.
[8] The production method according to any one of [1] to [7], wherein the step (3) is performed by mixing the slurry (a) with a dispersion liquid containing inorganic particles.
[9] The production method according to any one of [1] to [8], wherein the content of the inorganic particles in the slurry (b) is 0.0005 to 1% by mass.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a method for producing a thermoplastic resin powder capable of stably and continuously producing a powder for a long period of time.

Hereinafter, the present invention will be described in detail.
The method of the present invention for producing the thermoplastic resin powder is a step (1) of freezing the dispersion liquid containing the thermoplastic resin particles and melting the frozen dispersion liquid to form an agglomerate of the thermoplastic resin particles. The step (2) of obtaining the containing slurry (a), the step (3) of mixing at least one selected from the group consisting of the dispersion liquid after freezing and the slurry (a) with the inorganic particles, and the obtained aggregation. It has a step (4) of dehydrating a slurry (b) containing an object and inorganic particles. With this configuration, powder can be stably and continuously produced for a long period of time.

Although not limiting the present invention, the following can be considered as the reasons why the above-mentioned excellent effects are obtained. That is, it is considered that the inclusion of the inorganic particles in the slurry before dehydration (slurry (b)) disperses the inorganic particles in the dehydrated product after dehydration and alleviates the sticking between the agglomerates.

The type of the dispersion liquid containing the thermoplastic resin particles applied in the present invention is not particularly limited, and various dispersion liquids containing the thermoplastic resin particles can be used, but the agglomerates are easily adhered and the effect of the present invention is effective. It is preferably obtained by emulsion polymerization because it is more pronounced.

Examples of the dispersion liquid include those in which a thermoplastic resin having a solid property at room temperature is dispersed. Specifically, one or more selected from the monomers exemplified below are copolymerized. Examples thereof include a dispersion in which a thermoplastic resin obtained by copolymerization or graft polymerization is dispersed in a dispersion medium (for example, water, various organic solvents, etc.), or a mixed dispersion thereof. Examples of the monomer include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethyl methacrylate. Acrylate esters such as ethylhexyl; aromatic vinyls such as styrene, monoclonal styrene, dichlorostyrene, α-methylstyrene; N-isopropylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, NO-chlorophenylmaleimide and the like. N-substituted maleimide; vinyl cyanide such as acrylonitrile and methacrylonitrile; vinyl halide such as vinyl chloride, vinyl bromide and vinyl fluoride; vinylidene halide such as vinylidene chloride, vinylidene bromide and vinylidene fluoride; acrylic acid , Methacrylic acid, itaconic acid, maleic acid and other unsaturated carboxylic acids; ethylene, propylene, isoprene, 1,3-butadiene and other alkene; chloroprene; vinyl acetate; vinyl benzoate; allyl (meth) acrylate, diallyl phthalate, tri Examples thereof include polyfunctional monomers such as allyl cyanurate, monoethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, divinylbenzene, and glycidyl (meth) acrylate.

When the method of the present invention is applied to a dispersion liquid containing particles of a thermoplastic resin having excellent transparency as shown in the following (1) to (4), a powder having extremely excellent optical properties can be obtained. It is preferable because it can be done. Among these, it is more preferable to apply it to the dispersion liquid of (1).
(1) A dispersion liquid containing acrylic multilayer structure polymer particles having at least a layer of an acrylic soft polymer and a layer of an acrylic hard polymer outside the layer.
(2) A dispersion liquid containing at least a multilayer structure graft polymer particles having at least a layer of a polymer mainly containing a unit of a diene-based vinyl compound and a layer of a polymer containing a unit of a methacrylic acid alkyl ester on the outer side thereof.
(3) A dispersion liquid containing particles of a polymer mainly containing a unit of methacrylic acid alkyl ester.
(4) Any mixed dispersion of (1) to (3).

In the acrylic multilayer structure polymer particles in the dispersion liquid of (1) above, aggregates are easily adhered and the effect of the present invention is more prominently exhibited. The unit of the acrylic acid ester is 50 to 95% by mass, the unit of the other monofunctional monomer copolymerizable with the acrylic acid ester is 0 to 49.99% by mass, and the unit of the polyfunctional monomer is 0. It is preferably contained in an amount of 0.01 to 10% by mass.

As the acrylic acid ester constituting the unit of the acrylic acid ester, the acrylic acid ester exemplified above can be used as the monomer constituting the thermoplastic resin, and among these, butyl acrylate is preferable. The content of the acrylic acid ester unit in the acrylic soft polymer is more preferably 55 to 90% by mass, further preferably 60 to 85% by mass.

Examples of the other monofunctional monomer constituting the unit of the other monofunctional monomer include the methacrylic acid ester, aromatic vinyl, and N-substituted as the monomer constituting the thermoplastic resin. Maleimide, vinyl cyanide, vinyl halide, vinylidene halide, unsaturated carboxylic acid, alkene and the like can be used, and among these, aromatic vinyl is preferable, and styrene is more preferable. The content of the unit of the other monofunctional monomer in the acrylic soft polymer is more preferably 5 to 44.98% by mass, further preferably 10 to 39.9% by mass.

As the polyfunctional monomer constituting the unit of the polyfunctional monomer, the polyfunctional monomer exemplified above as the monomer constituting the thermoplastic resin can be used, and among these, the polyfunctional monomer can be used. Allyl (meth) acrylate is preferred. The content of the unit of the polyfunctional monomer in the acrylic soft polymer is more preferably 0.02 to 8% by mass, further preferably 0.1 to 5% by mass.

Since the acrylic multilayer structure polymer particles in the dispersion liquid of the above (1) exert the effect of the present invention more remarkably, the acrylic hard polymer constituting the acrylic hard polymer particles has 40 units of methacrylic acid ester. It preferably contains from 1 to 99% by mass and 1 to 60% by mass of other monomer units copolymerizable with the methacrylic acid ester.

As the methacrylic ester constituting the unit of the methacrylic ester, the methacrylic ester exemplified above can be used as the monomer constituting the thermoplastic resin, and among these, methyl methacrylate is preferable. The content of the unit of methacrylic acid ester in the acrylic hard polymer is more preferably 55 to 98% by mass, further preferably 80 to 97% by mass.

Examples of the other monomer constituting the unit of the other monomer include acrylic acid ester, aromatic vinyl, N-substituted maleimide, vinyl cyanide, which are exemplified above as the monomer constituting the thermoplastic resin. Vinyl halide, vinylidene halide, unsaturated carboxylic acid, alkene, polyfunctional monomer and the like can be used, and among these, acrylic acid ester is preferable, and methyl acrylate is more preferable. The content of the unit of the other monomer in the acrylic hard polymer is more preferably 2 to 45% by mass, further preferably 3 to 20% by mass.

In the present invention, there are no particular restrictions on the type and amount of the polymerization initiator, emulsifier, chain transfer agent, etc. used to obtain the dispersion, the polymerization temperature, the polymerization conditions such as the method for dropping the monomer, and the present invention has been widely used. The adopted polymerization conditions can be adopted.

Examples of the polymerization initiator include inorganic peroxides such as potassium persulfate, water-soluble redox-based initiators such as ammonium persulfate-sodium bisulfite, and oil-soluble redox initiators such as cumenehydroperoxide-sodium formaldehyde sulfiterate. Can be used.

Examples of the emulsifier include carboxylates such as sodium stearate, sulfonic acids such as dodecylbenzenesulfonic acid or salts thereof, and anionic surfactants such as esters or salts of organic or inorganic acids such as sodium lauroyl sarcosinate and sodium lauryl sulfate. The agent can be preferably used. Further, if necessary, at least one of a cationic surfactant and a nonionic surfactant can be used in combination.

In addition, examples of the chain transfer agent used as needed include mercaptans such as n-octyl mercaptan.
Further, if desired, a known additive such as an ultraviolet absorber or a dye can be added to the monomer to carry out the polymerization. The content of the thermoplastic resin particles in the dispersion liquid containing the thermoplastic resin particles is usually 10 to 60% by mass, preferably 20 to 50% by mass.

The average particle size of the thermoplastic resin particles is not particularly limited, but it is preferably 150 nm or less, preferably 140 nm or less, because agglomerates are easily adhered and the effect of the present invention is more remarkable. Is more preferable, and 130 nm or less is further preferable. The lower limit of the average particle size is not particularly limited, and the average particle size can be, for example, 50 nm or more. The average particle size can be obtained by a light scattering method using a dispersion liquid before freezing, and specifically, can be obtained by a method described later in Examples.

In the step (1), the dispersion liquid containing the thermoplastic polymer particles as described above is frozen. There are no particular restrictions on the freezing conditions and operation method at that time. By the freezing, the thermoplastic polymer particles can aggregate to form an agglomerate.

Next, in the step (2), the dispersion liquid (frozen body) after freezing obtained as described above is thawed. As a result, a slurry (slurry (a)) containing agglomerates of thermoplastic resin particles can be obtained. The method of thawing the dispersion after freezing is not particularly limited, and a method capable of raising the temperature of the dispersion after freezing can be adopted.

In the step (3), at least one selected from the group consisting of the above-mentioned post-frozen dispersion and the slurry (a) is mixed with the inorganic particles. That is, the mixing of the inorganic particles may be carried out with respect to the dispersion liquid after freezing, with respect to the slurry (a) obtained by melting the dispersion liquid, or with respect to both of them. good. When the dispersion liquid after freezing and the inorganic particles are mixed, the thawing according to the step (2) may be performed after that.

The type of inorganic particles is not particularly limited, and for example, inert inorganic particles such as silica, alumina, titanium oxide, calcium carbonate, and barium sulfate can be used. One type of these inorganic particles may be used alone, or two or more types may be used in combination. Among these, silica is preferable, and colloidal silica is more preferable, because the transparency when the finally obtained powder is blended with a transparent resin such as an acrylic resin is further improved.

The size of the inorganic particles is not particularly limited, but the powder is stably and continuously produced for a long period of time while ensuring the transparency when the finally obtained powder is blended with a transparent resin such as acrylic resin. The average particle size is preferably 4 to 50 nm, and more preferably 5 to 30 nm. The average particle size of the inorganic particles can be obtained by a light scattering method.

In the step (3), the inorganic particles may be mixed in the form of powder, but since the dispersibility can be improved and the effect of the present invention can be more remarkable, the dispersion containing the inorganic particles can be achieved. It is preferable to mix in the form of a liquid. As an example of such a method, there is a method of mixing the slurry (a) obtained in the step (2) with a dispersion liquid containing inorganic particles.

In particular, when the frozen dispersion obtained in step (1) and the dispersion containing inorganic particles are mixed, the frozen dispersion (frozen) in step (2) is thawed. The mixing of the inorganic particles in the step (3) can be performed substantially at the same time, and the productivity is improved. As a specific method for mixing the frozen dispersion (frozen body) and the dispersion containing inorganic particles, for example, after freezing in a dispersion containing warmed inorganic particles (water dispersion, etc.). A method of adding a dispersion liquid (frozen body) of the above can be mentioned. When the method of performing the step (2) and the step (3) substantially simultaneously as described above is adopted, the slurry (a) obtained in the step (2) is a slurry (b) containing agglomerates and inorganic particles described later. Can be considered to be. Inorganic particles (a dispersion liquid containing inorganic particles may be used) with respect to the slurry (a) obtained by adopting the method of performing steps (2) and (3) substantially simultaneously as described above. May be mixed.

Next, in the step (4), the slurry (b) containing the agglomerates and the inorganic particles obtained as described above is dehydrated. The content of the thermoplastic resin particles in the slurry (b) to be dehydrated is preferably 3% by mass or more, more preferably 5% by mass or more, and more preferably 50% by mass or less. It is preferably 30% by mass or less, more preferably 30% by mass or less. When the content is at least the above lower limit, the productivity of the powder is improved. Further, when the content is not more than the above upper limit, the slurry (b) has an appropriate viscosity and its handleability is improved.

Further, the content of the inorganic particles in the slurry (b) subjected to dehydration is stable and continuous for a long period of time while ensuring the transparency when the finally obtained powder is blended with a transparent resin such as an acrylic resin. It is preferably 0.0005 to 1% by mass, more preferably 0.005 to 0.5% by mass, and 0.01 to 0.1% by mass because it can produce powders. %, More preferably 0.02 to 0.05% by mass.

The temperature of the slurry (b) to be dehydrated is preferably 20 to 95 ° C, more preferably 30 to 90 ° C. When the temperature is at least the above lower limit, the cohesive force of the thermoplastic resin particles is maintained, and the crushing of the agglomerates during dehydration and washing can be more effectively suppressed. Further, when the temperature is not more than the above upper limit, blocking can be effectively suppressed.

The specific method of dehydration is not particularly limited, and for example, a method using a centrifuge such as a bucket type or a decanter type can be adopted. After dehydration, washing may be performed if necessary, or the dehydrated product after dehydration may be dispersed in a dispersion medium and then dehydrated again.

The desired thermoplastic resin powder can be obtained by further drying the dehydrated product after dehydration (after washing if necessary), if necessary. Drying can be performed using, for example, a flow dryer, a vibration dryer, a hot air dryer (circulation type dryer, etc.) and the like.

The thermoplastic resin powder obtained by the production method of the present invention may contain known additives such as anti-adhesion agents, ultraviolet absorbers, lubricants, antioxidants, dyes, etc., depending on the purpose of use thereof and the like. ..

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
The evaluation methods adopted in the following examples and comparative examples are shown below.

-Average particle size of thermoplastic resin particles The dispersion obtained in the production example below is diluted to 0.005% by mass with deionized water, and an ultraviolet-visible absorbance photometer "UVmini 1240" (manufactured by Shimadzu Corporation) is used. The absorbance at 350 nm was measured using. From the obtained absorbance value, the average particle size was obtained using a correlation formula between the absorbance and the particle size.

-Adhesion resistance test 30 g of the dehydrated product obtained in the following Example or Comparative Example was placed in a 61 mmφ cylindrical container, loaded at 0.211 kg / cm ² for 5 minutes, and then the obtained cake was sieved by an electromagnetic sieve. It was broken with a shaker "MVS-200" (manufactured by C.M.T. Co., Ltd.), and the time until the whole collapsed was measured.

[Manufacturing example]
In a reactor equipped with a stirrer, thermometer, nitrogen gas introduction part, monomer introduction tube and reflux condenser, 150 parts by mass of deionized water, 3 parts by mass of sodium stearate and 0.05 parts by mass of sodium carbonate were placed. After charging and sufficiently replacing the inside of the container with nitrogen gas to make it substantially free of oxygen, the internal temperature was set to 80 ° C. 0.04 part by mass of potassium persulfate was added thereto, and after stirring for 5 minutes, 11.2 parts by mass of methyl methacrylate, 24 parts by mass of n-butyl acrylate, 4.6 parts by mass of styrene and 0. A monomer mixture consisting of 2 parts by mass was continuously added dropwise over 60 minutes, and after the addition was completed, a polymerization reaction was further carried out for another 30 minutes so that the polymerization rate was 98% or more.
Next, 0.02 part by mass of potassium persulfate was put into the reactor and stirred for 5 minutes, then 0.8 part by mass of methyl methacrylate, 16 part by mass of n-butyl acrylate, and 3.1 part by mass of styrene. A monomer mixture consisting of 0.1 part by mass of and allyl methacrylate was continuously added dropwise over 30 minutes, and after the addition was completed, a polymerization reaction was further carried out for another 30 minutes so that the polymerization rate was 98% or more.
Further, 0.04 part by mass of potassium persulfate was put into the reactor and stirred for 5 minutes, then 37.7 parts by mass of methyl methacrylate, 2 parts by mass of n-butyl acrylate and n-octyl mercaptan (chain). (Transfer agent) A monomer mixture consisting of 0.3 parts by mass was continuously added dropwise over 100 minutes, and after the addition was completed, a polymerization reaction was further carried out for 60 minutes so that the polymerization rate was 98% or more.
In this way, a dispersion liquid containing thermoplastic resin particles (acrylic multilayer structure polymer particles) was obtained. The average particle size of the thermoplastic resin particles was 120 nm.

[Example 1]
Using the dispersion liquid containing the thermoplastic resin particles obtained in the above production example, the thermoplastic resin powder was continuously produced by the following method.
That is, first, 10 kg of the above dispersion was frozen in a freezer at −30 ° C. No unfrozen part was found.
On the other hand, 10 kg of deionized water was charged into a melting tank equipped with a stirrer, a thermometer and a jacket. The temperature of the deionized water is raised to 40 ° C., and when the deionized water reaches that temperature, 8 g of colloidal silica (“Snowtex O”, manufactured by Nissan Chemical Industries, Ltd.) is added as inorganic particles to the dispersion liquid containing the inorganic particles. And said.
The frozen dispersion was added to the dispersion containing the inorganic particles and thawed to obtain a slurry (slurry (b)) containing the aggregates and the inorganic particles. Subsequently, this slurry (b) was taken out, dehydrated and washed with a centrifuge to obtain a dehydrated product, and then dried with a circulation type dryer at 80 ° C. to obtain a thermoplastic resin powder. When the sticking resistance test was performed by the above method using the above-mentioned dehydrated product, it was 30 seconds.
By the above method, the thermoplastic resin powder could be continuously produced for 2 weeks or more.

[Comparative Example 1]
The thermoplastic resin powder was continuously produced in the same manner as in Example 1 except that no inorganic particles were added, but the piping was blocked 4 hours after the start of the dehydration operation, and it became necessary to interrupt the production. rice field. The result of the sticking resistance test was 50 seconds.

[Comparative Example 2]
The thermoplastic resin powder was continuously produced in the same manner as in Example 1 except that the inorganic particles were added to the dispersion liquid containing the thermoplastic resin particles before freezing instead of the deionized water, but the dehydration operation was started. Three days later, the piping was blocked, and it became necessary to suspend production. The result of the sticking resistance test was 45 seconds.

Claims (5)

A step (1) of freezing the dispersion liquid containing the thermoplastic resin particles, a step (2) of melting the frozen dispersion liquid to obtain a slurry (a) containing an aggregate of the thermoplastic resin particles, and the step after freezing. The step (3) of mixing at least one selected from the group consisting of the dispersion liquid of the above and the slurry (a) with colloidal silica (excluding the silicone-based defoaming agent obtained by adding colloidal silica to silicone oil ). It has a step (4) of dehydrating the slurry (b) containing the aggregates and inorganic particles obtained;
The thermoplastic resin particles are acrylic multilayer structure polymer particles having at least an acrylic soft polymer layer and an outer acrylic hard polymer layer;
The acrylic soft polymer has a unit of acrylic acid ester of 50 to 95% by mass, a unit of another monofunctional monomer copolymerizable with the acrylic acid ester of 0 to 49.99% by mass, and polyfunctionality. Contains 0.01-10% by weight of sex monomer units;
The steps (2) and (3) are performed by mixing the frozen dispersion with the colloidal silica-containing dispersion;
A method for producing thermoplastic resin powder. The production method according to claim 1, wherein the dispersion liquid containing the thermoplastic resin particles is obtained by emulsion polymerization. Claim 1 or 2 , wherein the acrylic hard polymer contains 40 to 99% by mass of a unit of methacrylic acid ester and 1 to 60% by mass of another monomer copolymerizable with the methacrylic acid ester. The manufacturing method described. The production method according to any one of claims 1 to 3 , wherein the thermoplastic resin particles have an average particle diameter of 150 nm or less. The production method according to any one of claims 1 to 4 , wherein the content of colloidal silica in the slurry (b) is 0.0005 to 1% by mass.