JP6026769B2 - Method for producing aqueous dispersion of thermoplastic resin - Google Patents

Description

  The present invention relates to a method for producing an aqueous dispersion of a thermoplastic resin by a mechanical emulsification method.

  There are various known methods for producing dispersions, so-called emulsions, in which thermoplastic substances such as polyethylene, polypropylene, and ethylene / vinyl acetate copolymers are dispersed in water using a dispersant such as a surfactant or protective colloid. ing.

  For example, in the case of an ethylene / vinyl acetate copolymer, the ethylene / vinyl acetate copolymer is first heated and melted, then an anionic or nonionic surfactant is added and stirred, and then hot water is added. Then, it is obtained by emulsification using a mechanical shearing force such as a homomixer (see Patent Document 1).

  This emulsifier may bleed out during use of the obtained product, and the ester part of partially saponified polyvinyl alcohol may be hydrolyzed to generate acetic acid. It may not be usable.

  In contrast, a method for producing an aqueous polymer dispersion using a neutralized product of a specific acrylic copolymer with improved emulsification stability as an anionic water-soluble polymer dispersant (see Patent Document 2), low temperature A method for producing a polymer aqueous dispersion using a neutralized product of a specific acrylic copolymer having excellent film-forming properties as a cationic water-soluble polymer dispersant is known (see Patent Document 3). These are all emulsified using mechanical shearing force such as a homomixer.

JP 57-061035 A JP 58-127752 A JP 58-118843 A

  However, in these methods, separation may occur when a large amount of the polymer emulsion is added, and kneading may be difficult. When this state occurs, the resulting emulsion particles tend to be large and non-uniform in size.

  Accordingly, an object of the present invention is to solve such problems and to obtain an aqueous thermoplastic resin dispersion having uniform emulsion particles with a small particle size.

  This invention relates to a method for producing an aqueous dispersion of a thermoplastic resin by a mechanical emulsification method, wherein a polymer emulsifier is used as an emulsifier / dispersant, and the polymer emulsifier is added in several portions. By making it a feature, the above-mentioned problems have been solved.

  In particular, the first addition of the polymer emulsifier is 50% by weight or more and 99% by weight or less of the total addition amount, and the second and subsequent additions are equally divided or gradually reduced according to the number of divided additions. Thus, it is preferable to add in portions.

  Since the polymer emulsifier is added in several portions, it is possible to suppress separation during emulsification of the thermoplastic resin, enabling efficient kneading and obtaining uniform emulsion particles with a small particle size. .

  In particular, the first addition of the polymer emulsifier is 50% to 99% by weight of the total addition amount, and the second and subsequent additions are equally divided or gradually decreased depending on the number of divided additions. By adding in divided portions, kneading can be performed more efficiently, and emulsion particles having a small particle size can be obtained more uniformly.

Schematic diagram showing an example of an extruder used in the present invention

The present invention will be described in detail below.
The method for producing an aqueous dispersion of a thermoplastic resin according to the present invention is a method for producing an aqueous dispersion of a thermoplastic resin by a mechanical emulsification method.

[Thermoplastic resin]
The thermoplastic resin refers to a thermoplastic resin to be dispersed.
Examples of this thermoplastic resin include polyolefin resins, modified polyolefin resins, acrylic resins, rubber substances, and the like.

  Examples of the polyolefin resin include ethylene such as low density polyethylene, propylene, ethylene / vinyl acetate copolymer, ethylene / propylene random copolymer, ethylene / acrylic acid copolymer and ester or salt thereof, and ethylene / methacrylic acid copolymer. Polymers or salts thereof, ethylene / methacrylic acid ester copolymers or salts thereof, so-called ethylene-based crystalline ethylene copolymers such as ethylene / ethyl acrylate / maleic anhydride copolymers, propylene / hexene copolymers Examples thereof include crystalline propylene-based copolymers mainly composed of propylene such as polymers and propylene / butene copolymers.

  Examples of the modified polyolefin resin include halogenated polyolefin and unsaturated carboxylic acid-modified polyolefin. Specific examples of the halogenated polyolefin include chlorinated polyethylene and chlorinated polypropylene. Examples of the unsaturated carboxylic acid-modified polyolefin include polyolefins modified with an unsaturated carboxylic acid such as maleic anhydride. This maleic anhydride is easily available and economical. The amount of maleic anhydride used, that is, the amount of modification is preferably from 0.1 to 20% by weight, and preferably from 0.1 to 10% by weight. If it is less than 0.1% by weight, the effect of modification tends not to be fully exhibited. On the other hand, when it is more than 20% by weight, the emulsification tends to be unstable.

  Examples of the rubber material include polybutylene, polyisobutylene, ethylene / propylene copolymer rubber, liquid polybutadiene and modified products thereof, and ethylene / propylene / diene terpolymer rubber.

  Other thermoplastic resins include polyethylene wax, ester wax, carnauba wax, Fischer-Trops wax, microcrystalline wax, paraffin wax and oxides thereof, low molecular weight polyamide, amide compounds such as fatty acid amide, terpenes and the like Derivatives, rosin and derivatives thereof, petroleum resins and derivatives thereof, low molecular weight styrene resins and derivatives thereof, and the like.

  Among these, polyolefin-based resins and modified polyolefin-based resins are preferable in that they are easily available as general-purpose resins and have characteristics that the resins themselves are easily emulsified.

  The thermoplastic resin preferably has a melting point and a Vicat softening point of 200 ° C. or lower. When the temperature exceeds 200 ° C., the emulsion particles of the aqueous dispersion obtained are irregular and have a large particle size, which may deteriorate the stationary stability of the aqueous dispersion.

[Polymer emulsifier]
A polymer emulsifier can be used as an emulsifier / dispersant for emulsifying / dispersing the thermoplastic resin.
By using a polymer-based emulsifier as the emulsifier, when kneaded with the thermoplastic resin to be emulsified and dispersed, the affinity with the thermoplastic resin is improved, so that the resulting resin aqueous dispersion can be used for a long time. , Stable separation can be maintained.

  As the emulsifier, a polymer emulsifier is preferably used, but a low molecular emulsifier may be used in combination as long as the effect thereof is not impaired. Examples of the low molecular weight emulsifier include anionic emulsifiers such as sodium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium alkylsulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate. In addition to the sodium salt, a corresponding potassium salt or calcium salt may be used. Nonionic emulsifiers usually include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester having a weight average molecular weight of 5000 or less. It is done. Furthermore, examples of amphoteric emulsifiers include lauryl betaine and lauryl dimethylamine oxide.

Examples of the polymer emulsifier include a cationic polymer (hereinafter referred to as “cationic polymer emulsifier”) and an anionic polymer (hereinafter referred to as “anionic polymer emulsifier”). ), A non-ionic polymer having both hydrophilic / lipophilic segments (hereinafter referred to as “nonionic polymer emulsifier”), and both cationic and anionic properties. And a high molecular weight copolymer (hereinafter referred to as “amphoteric high molecular emulsifier”).
In the present specification, the term “(meth) acryl” means “acryl or methacryl”. Further, in this specification, “contained as a main component” means a component containing 50% by weight or more of the component corresponding to the main component with respect to the whole.

[Polymer emulsifier-cationic polymer emulsifier]
The cationic polymer emulsifier refers to a copolymer of a monomer mixture containing a cationic monomer. Examples of the cationic monomer include alkylaminoalkyl (meth) acrylate and dialkylaminoalkyl (meth) acrylamide.

  Examples of the cationic polymer emulsifier include dialkylaminoalkyl (meth) acrylate-alkyl (meth) acrylate copolymers, dialkylaminoalkyl (meth) acrylamide- (meth) acrylic acid alkyl ester copolymers, and the like. .

  In particular, the number of carbon atoms of the alkyl group substituted with the alkylamino group of the alkylaminoalkyl (meth) acrylate is preferably in the range of 1 to 6. Examples of such alkylaminoalkyl (meth) acrylates include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and the like.

  The copolymer constituting the cationic polymer emulsifier can be quaternized, that is, cationized, by neutralizing the monomer mixture before or after the copolymerization.

  An acidic compound is used as the neutralizing agent used for the neutralization. Examples of the acidic compound include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as oxalic acid, formic acid, and acetic acid. Among these, vapor pressure that hardly remains in the film obtained from the thermoplastic resin dispersion liquid. A neutralized (meth) acrylic acid alkylaminoalkyl ester copolymer using a high neutralizing agent such as formic acid or acetic acid is more preferred as the cationic polymer emulsifier. The neutralizing agent is desirably used in an amount of 60 mol% to 150 mol% with respect to the functional group exhibiting cationic properties.

  If the amount is less than this range or is used in excess of this range, the stability of the aqueous thermoplastic resin dispersion tends to deteriorate in any case.

  The content of the structural unit derived from the cationic monomer in the cationic polymer emulsifier is required to be 1 mol% or more with respect to the total thermoplastic resin component, and preferably 2 mol% or more. When the amount is less than 1 mol%, the dispersion stability tends to decrease. On the other hand, the upper limit of the content is preferably 85 mol%, and preferably 80 mol%. When it is more than 85 mol%, the dispersion stabilizing effect may be lowered.

[Polymer emulsifier-Anionic polymer emulsifier]
As the above-mentioned polymer emulsifier exhibiting anionic property, the co-polymerization of a monomer mixture containing a monomer containing an anionic monomer having a carboxyl group, a sulfonic acid group, a phosphoric acid group, an acidic phosphate group, etc. Refers to coalescence. Examples of such a monomer include acrylamide-2-methylpropane sulfonic acid as a sulfonic acid group-containing monomer. Moreover, mono (2-methacryloyloxyethyl) acid phosphate etc. are mentioned as an acidic phosphate ester group containing monomer.

  Preferred monomers as the carboxyl group-containing monomer include (meth) acrylic acid, itaconic acid, citraconic acid, maleic acid, crotonic acid, fumaric acid, maleic acid monoalkyl ester, and fumaric acid monoalkyl ester. Can be mentioned.

  Particularly preferred as the anionic polymer emulsifier is a copolymer using a monomer containing a carboxyl group, particularly a copolymer using maleic acid, such as a styrene-maleic acid copolymer and a partial ester thereof. And a copolymer using (meth) acrylic acid, for example, a (meth) acrylic acid copolymer.

  The content of the structural unit derived from the anionic monomer in the anionic polymer emulsifier is required to be 5 mol% or more as a copolymerization component, and preferably 10 mol% or more. When it is less than 5 mol%, the stabilizing effect as a polymer emulsifier is lowered. On the other hand, the upper limit of the content is preferably 80 mol%, and preferably 70 mol%. If the amount is more than 80 mol%, the stabilizing effect of the aqueous thermoplastic resin dispersion tends to decrease, and further, the water resistance of the resulting aqueous thermoplastic resin dispersion decreases, and the dry film becomes hard. The heat sealability at low temperatures may be reduced, or the dry film may become cloudy.

  Moreover, you may neutralize the functional group which shows the said anionicity with the neutralizing agent which consists of an alkaline substance. Examples of the neutralizing agent include ammonia and sodium hydroxide. The neutralizing agent is desirably used in an amount of 60 mol% to 150 mol% based on the functional group exhibiting anionic property. If the amount is less than this range or is used in excess of this range, the stability of the aqueous thermoplastic resin dispersion tends to deteriorate in any case.

  Among these, particularly preferable as the anionic polymer emulsifier is, from the viewpoint of water resistance of the film obtained from the aqueous dispersion of the thermoplastic resin, a neutralizer having a high vapor pressure that hardly remains in the film, for example, ammonia. (Meth) acrylic acid alkyl ester copolymer neutralized by use. These anionic polymer emulsifiers may be used in combination of two or more.

[Polymer emulsifier-nonionic polymer emulsifier]
Examples of the nonionic polymer emulsifier include partially saponified polyvinyl alcohol, a block copolymer of ethylene oxide and propylene oxide, and hydroxyethyl cellulose.

Among these nonionic polymer emulsifiers, the reactive emulsifier represented by the formula (1) is particularly preferable.
R ^1- (C _n H _2n O) _m -R ² (1)
In the formula, R ¹ represents a group selected from the following two groups (a) and (b), R ² represents H or an alkyl group having 1 to 4 carbon atoms, and n represents 1 to 3 M represents an integer of 4 to 25.
(A) (meth) acryloyloxy groups _(CH 2 = CH-COO- or _{CH 2 = C (CH 3)} -COO-)
(B) (meth) acryloyloxy ethoxy _{(CH 2 = CH-COO-} CH 2 -CH 2 -O- or _{CH 2 = C (CH 3)} -COO-CH 2 -CH 2 -O-)

  Specific examples of the nonionic reactive emulsifier represented by the above formula (1) include methoxytetraethylene glycol (meth) acrylate, ethoxytetraethylene glycol (meth) acrylate, propoxytetraethylene glycol (meth) acrylate, n -Butoxytetraethylene glycol (meth) acrylate, n-pentoxytetraethylene glycol (meth) acrylate tetrapropylene glycol (meth) acrylate, methoxytetrapropylene glycol (meth) acrylate ethoxytetrapropylene glycol (meth) acrylate, propoxytetrapropylene glycol (Meth) acrylate, n-butoxytetrapropylene glycol (meth) acrylate, n-pentatetrapropylene glycol (me ) Acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate and the like. Among these, those having a polyethylene glycol chain having 2 to 25 ethylene glycol group repeating units are more preferable. If the number of repeating units is less than 2, the dispersion stability tends to decrease. If it is more than 25, the hydrophilic group is solidified at a normal temperature, so that a sufficient dispersion stabilizing effect may not be obtained. is there. Two or more kinds of these nonionic emulsifiers may be used in combination.

[Polymer emulsifier-Amphoteric polymer emulsifier]
The amphoteric polymer emulsifier comprises a polymer copolymer exhibiting both cationic and anionic properties. The amphoteric polymer emulsifier refers to a copolymer obtained by copolymerizing a monomer mixture containing the above anionic monomer and the above cationic monomer. As the anionic monomer and the cationic monomer, the same ones as described above can be used.

  The monomer mixture used for the amphoteric polymer emulsifier may contain other copolymer monomers composed of nonionic monomers in addition to the anionic monomers and cationic monomers. . As this nonionic monomer, the same ones as described above can be used.

  The total equivalent number of cationic groups derived from the cationic monomer used in the amphoteric polymer emulsifier is less than the total equivalent number of anionic groups derived from the anionic monomer used in the amphoteric polymer emulsifier. Is preferred.

  Specific examples of the mixing ratio of the cationic monomer and the anionic monomer used in the amphoteric polymer emulsifier include the following ranges. That is, the compounding ratio of the cationic group derived from the cationic monomer and the anionic group derived from the anionic monomer is an equivalent ratio, and the cationic group / anionic group is preferably less than 50/50, and 40 / 60 or less is preferable. When it is 50/50 or more, it tends to be difficult to mix and use with an anionic aqueous dispersion which is used for general purposes. On the other hand, the lower limit of the blending ratio is preferably 10/90, and preferably 20/80. If it is less than 10/90, it may cause an increase in the film forming temperature of the resulting aqueous dispersion, thereby deteriorating the low-temperature adhesion and transparency of the resulting dried film, and its use may be limited.

  In addition, the content of the nonionic monomer is preferably 90 mol% or less, and preferably 85 mol% or less, based on the whole monomer used in the amphoteric polymer emulsifier. If the amount is more than 90 mol%, the hydrophilicity of the neutralized product may be lowered, and a stable aqueous polymer dispersion may not be produced. On the other hand, the lower limit of the content ratio is preferably 10 mol%, preferably 20 mol%, more preferably 30 mol%. When the amount is less than 10 mol%, the hydrophilicity when neutralized becomes too high, and there is a tendency that a stable polymer aqueous dispersion cannot be obtained.

In amphoteric polymer emulsifiers, functional groups that exhibit anionic properties are neutralized with alkaline substances such as ammonia and sodium hydroxide, and cationic functional groups that are neutralized with acidic substances such as formic acid and acetic acid. Each may be neutralized with an agent. In any case, it is desirable that the neutralizing agent is used in an amount of 60 mol% to 150 mol% with respect to the anionic or cationic functional group. If it is less than this range or exceeds this range, in any case, the dispersed thermoplastic resin particles tend to be excessively large or the stability of the aqueous thermoplastic resin dispersion tends to deteriorate. .
Two or more of these amphoteric polymer emulsifiers may be used in combination.

[Production of polymer emulsifier]
The copolymer constituting the above polymer emulsifier is each weighed each monomer component and then polymerized by adding each component individually to a polymerization vessel, or each monomer is premixed It can manufacture by adding to a superposition | polymerization apparatus and polymerizing above. This copolymerization reaction is usually carried out in the presence of a polymerization initiator at 0 to 180 ° C., preferably 40 to 120 ° C. for 0.5 to 20 hours, preferably 2 to 10 hours. Is called. This polymerization is preferably carried out in the presence of a hydrophilic solvent such as ethanol, isopropanol, cellosolve or water.

As the monomer raw material, the above cationic monomer and nonionic monomer are used in the cationic polymer emulsifier, and the above anionic monomer and nonionic monomer are used in the anionic polymer emulsifier. In addition, in the amphoteric polymer emulsifier, the anionic monomer, the cationic monomer, and, if necessary, the nonionic monomer are within the range of the above-described constituent ratio. Prepare to. In the amphoteric polymer emulsifier, as described above, the anionic group equivalent derived from the anionic monomer was used because it was used in excess of the equivalent cationic group derived from the cationic monomer. A monomer mixture will show anionicity as a whole.
A nonionic polymer emulsifier can be produced by introducing a hydrophilic segment and a lipophilic segment into a polymer chain by block copolymerization or the like as described above.

  In addition, as a polymerization initiator, an initiator composed of a persulfate such as ammonium persulfate, potassium persulfate, sodium persulfate, etc., a redox initiator using the above-mentioned persulfate in combination with a sulfite, a thiosulfate reducing agent, Redox initiators using organic peroxides such as lauroyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, etc., or iron (II) salt, sulfite, thiosulfate reducing agents, etc. -Azobis (isobutyronitrile), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2'-azobis [2- (2-imidazolin-2-yl) Propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) dihydrochloride and other azo compounds, t-butyl Oxy isobutyrate, 1,1-bis (t-butylperoxy) cyclohexene, t- butyl peroxybenzoate, and the like. The amount of the polymerization initiator used is preferably 0.01 to 10% by weight based on the total amount of monomers used.

  The neutralization reaction is carried out by reacting the copolymer with an acidic compound or basic compound at 20 to 100 ° C. for 0.1 to 3 hours.

Moreover, the anionic monomer or cationic monomer used for the monomer raw material may be neutralized with a neutralizing agent in advance and then provided to the copolymerization.
The obtained neutralized product is generally used as an aqueous solution of 5 to 50% by weight.

  The weight average molecular weight of the polymer emulsifier is preferably in the range of 1,000 to 1,000,000. If it is less than 1,000, the stability of the aqueous dispersion of the thermoplastic resin may be lowered and dispersion may not be possible. On the other hand, if it exceeds 1,000,000, the polymer emulsifier becomes difficult to dissolve in water, and the stability of the aqueous thermoplastic resin dispersion tends to deteriorate. A more preferred weight average molecular weight of the polymer emulsifier is 2,000 to 100,000, and a more preferred weight average molecular weight is 50,000 to 80,000.

  When the polymer emulsifier is obtained as an aqueous solution or an aqueous dispersion, the viscosity of the aqueous solution or aqueous dispersion is preferably 1,000 mPa · s or more, more preferably 10,000 mPa · s or more at a measurement temperature of 50 ° C. On the other hand, the upper limit of the viscosity is preferably 100,000 mPa · s, more preferably 80,000 mPa · s. If it is out of these ranges, the emulsifying performance as a polymer emulsifier may be insufficient, a long time may be required for the addition, or it may remain in the addition container or the like, making it difficult to add a desired amount.

  When the polymer emulsifier is obtained as an aqueous solution or aqueous dispersion, the concentration of the polymer emulsifier in the aqueous solution or aqueous dispersion of the polymer emulsifier is preferably 5% by weight or more, and more preferably 10% by weight or more. If it is less than 5% by weight, the concentration of the polymer emulsifier in the aqueous thermoplastic resin dispersion is lowered, and the dispersion stability may be lowered. On the other hand, the upper limit of the concentration is preferably 80% by weight, and more preferably 50% by weight. If the concentration is higher than 80% by weight, the water content of the aqueous thermoplastic resin dispersion may be insufficient, and good dispersion stability may not be obtained.

  The amount of the polymer emulsifier used is preferably 2 to 40 parts by weight with respect to 100 parts by weight of the thermoplastic resin in terms of stability of the resulting dispersion and water resistance of the resulting film. More preferably, it is 2 to 20 parts by weight. If it is less than 2 parts by weight, the stability of the aqueous thermoplastic resin dispersion may be lowered. If it exceeds 40 parts by weight, the water resistance of the resulting film may be lowered, and at the same time, the heat sealability may be lowered.

[Mechanical emulsification method]
The mechanical emulsification method is a method of kneading and emulsifying a thermoplastic resin in the presence of an aqueous medium such as an emulsifying / dispersing agent and water using a kneader such as an extruder, a kneader, an ink roll, Instead of kneading, a homogenizer, a disper or the like is used to perform a homogenization treatment with a shearing force.

  As the above-mentioned extruder, there are single-screw and multi-screw extruders of two or more axes, but a twin-screw extruder is preferable from the viewpoint of kneading degree and efficiency. As an example of this extruder, a multi-screw extruder having two or more screws in a casing (see Japanese Patent Application Laid-Open No. 56-2149) can be cited.

  As a method of mechanical emulsification by this extruder, the thermoplastic resin is introduced from the inlet and inlet of the extruder, and an aqueous medium such as the emulsifying / dispersing agent and water is introduced from another inlet. It is generally kneaded, mixed and emulsified.

  The cylinder temperature of the extruder is preferably 40 to 270 ° C. Further, a treatment time of about 20 seconds to 20 minutes is sufficient.

  By the way, when the aqueous dispersion of the thermoplastic resin is manufactured using an extruder, it can be continuously manufactured.

[Production of aqueous dispersion of thermoplastic resin]
The aqueous thermoplastic resin dispersion according to the present invention is obtained by mixing the thermoplastic resin and the polymer emulsifier as an emulsifier / dispersant. The total addition amount of the polymer emulsifier (solid content) is preferably 3% by weight or more and preferably 5% by weight or more when the thermoplastic resin (solid content) is 100% by weight. When it is less than 3% by weight, it is difficult to produce a stable aqueous dispersion. On the other hand, the upper limit of the addition amount is preferably 30% by weight, more preferably 20% by weight. When it is more than 30% by weight, the mechanical strength of the resulting film may not be practically used, and the adhesion of the obtained film to a substrate such as paper, aluminum foil, or film tends to decrease.

  Further, the content of the thermoplastic resin is preferably 30% by weight or more, and preferably 40% by weight or more, with respect to the entire aqueous thermoplastic resin dispersion. If it is less than 30% by weight, it takes time to dry after applying the aqueous dispersion, and the adhesion tends to be insufficient. On the other hand, the upper limit of the content is preferably 90% by weight, and preferably 80% by weight. When the amount is more than 90% by weight, dispersion tends to be unstable, and preparation of an aqueous dispersion tends to be difficult.

  As a method for producing an aqueous dispersion of a thermoplastic resin according to the present invention using the above-mentioned polymer emulsifier, for example, a molten thermoplastic resin is added to a mixture of the polymer emulsifier and water, and uniformly mixed by an extruder. The above-mentioned mechanical emulsification methods such as a kneading method can be mentioned.

As a more preferable embodiment of the mechanical emulsification method using an extruder, the following methods can be exemplified.
As shown in FIG. 1, the thermoplastic resin A is continuously supplied from a hopper 12 of an extruder 11. Then, the polymer emulsifier B (B1 to B3) is pressurized and supplied from an intermediate inlet 13 provided in at least one of the melting zone and the kneading zone of the extruder, and this and the molten thermoplastic resin are melt-kneaded with a screw. To do. And as needed, the hot water C is pressurized and supplied from the halfway inlet 13 and dispersed. In addition, in the extruder 11, the inlets A to B1 are generally melting zones and the inlets B2 to C are generally kneading zones. A compression zone and a metering zone are provided between the inlet C and the outlet 14.

The polymer emulsifier B (B1 to B3) is added by being divided into a plurality of times as shown in FIG. Thereby, kneading can be performed more efficiently, and emulsion particles having a small particle diameter can be obtained more uniformly.
The polymer emulsifier may be added from the same inlet or from different inlets as long as it is divided.
A more preferable addition method is a method in which divided addition is performed in the downstream direction of the extruder, and charging is sequentially performed from different charging ports.

  The first addition of the polymer emulsifier is preferably 50% by weight or more, more preferably 60% by weight or more of the total addition amount. If it is less than 50% by weight, the degree of contact kneading between the thermoplastic resin and the polymer emulsifier is insufficient, which may cause a problem that it is difficult to obtain a good aqueous dispersion. On the other hand, the upper limit of the first addition is preferably 99% by weight, and more preferably 80% by weight. When the amount is more than 99% by weight, the particle diameter of the thermoplastic resin in the obtained aqueous dispersion becomes large, and the storage stability tends to deteriorate.

  The second and subsequent additions of the above-mentioned polymer emulsifier may be added in equal portions or divided so as to gradually decrease depending on the number of divided additions. As described above, as described above, as described above, in the case of FIG. 1, the first polymer emulsifier (B1) is added at the middle inlet 13a near the hopper, and the outlet 14 side of the middle inlet 13a is added. Addition of the second polymer emulsifier (B2) at the middle inlet 13b, and addition of the third polymer emulsifier (B3) at the middle inlet 13c on the outlet 14 side from the middle inlet 13b. Can be illustrated.

  In addition, after supplying all the polymer emulsifiers, the above-mentioned thermoplastic resin and the polymer emulsifier are kneaded by supplying warm water C at the intermediate inlet 13d downstream (on the outlet 14 side) from the intermediate inlet 13c. Concentration adjustment suitable for water dispersion of the product can be performed.

  For this reason, when the first addition of the polymer emulsifier is performed at the halfway inlet in the kneading zone of the extruder 11, distribution mixing and dispersion mixing are performed in a well-balanced manner, and the thermoplasticity is more uniform and has a smaller particle size. This is preferable in that an aqueous resin dispersion can be obtained.

  In addition, when performing addition several times, when divided addition is performed so that the addition amount is increased later, the kneading time becomes longer and the particle size of the resulting emulsion tends to increase.

  In the present invention, the polymer emulsifier is added a plurality of times, and as a preferred embodiment, the first addition amount is set to 50% by weight or more of the total addition amount, and the addition amount is the same in subsequent additions. Is to reduce. As a result, the viscosity ratio between the viscosity of the thermoplastic resin to be kneaded and the viscosity of the polymer emulsifier during addition mixing can be close to 1, and kneading of the thermoplastic resin and the polymer emulsifier can be performed efficiently. It becomes.

This viscosity ratio will be explained in more detail. When adding the above-mentioned polymer emulsifier, the viscosity of the polymer emulsifier is η _disp, and the viscosity of the resin in the extruder at the addition site of the polymer emulsifier is η _resin. The ratio value η _R (η _resin / η _disp ) is preferably larger than 0.1, and more preferably larger than 0.3. If it is less than 0.1, only a thermoplastic resin having a lower melt viscosity may flow, resulting in a problem that uniform kneading becomes difficult. On the other hand, the upper limit of the ratio value η _R is preferably 10, and is preferably 5. If it is greater than 10, only the low-viscosity polymer emulsifier flows, and uniform kneading may still be difficult.

  In the thermoplastic resin aqueous dispersion according to the present invention, an antifoaming agent, a viscosity adjusting agent, a low molecular emulsifier, an antioxidant, as necessary, in addition to the above components, unless the purpose and effect of the present invention are impaired. An agent may be blended.

  The aqueous thermoplastic resin dispersion produced in this way is one in which thermoplastic substance particles have an average particle size of 10 μm or less and are dispersed in water. This thermoplastic resin aqueous dispersion is used as a coating material, adhesive, ink binder, adhesive, adhesive, emulsion modifier, polyolefin substrate primer, etc., depending on the type of thermoplastic material used. be able to.

Hereinafter, the present invention will be described more specifically using examples. In addition, this invention is not limited to a following example, unless the summary is exceeded.
First, each evaluation method and raw materials are described below.

<Evaluation method>
[Volume average particle diameter]
Using a laser diffraction type particle size distribution measuring device (manufactured by Shimadzu Corporation: SALD-2200), the volume average particle diameter and the content ratio (% by weight) of large particles of 10 μm or more were measured.

[transparency]
Haze was measured according to JIS K7136: 2000 using a turbidimeter (Nippon Denshoku Industries Co., Ltd .: NDH5000).

[Buts]
According to JIS K5600-2-5: 1999, the size of the bumps was measured using a grind gauge.

[Emulsion stability]
200 g of the thermoplastic resin dispersion was placed in a 250 ml plastic container, and stored in a dryer at 50 ° C., and changes over time such as skinning and resin float were observed and evaluated according to the following criteria.
○: Skinning and resin float were not seen.
X: Skinning, resin floating, etc. were seen.

[Viscosity measurement]
The viscosity at 50 ° C. was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd .: VISCOMETER TVB-10M, −10H).

[Temperature viscosity curve]
A temperature-viscosity curve was measured using a rheometer (REOLOGICA INSTRUMENTS AB: VAR-100AD Rheometer manufactured by Jusco International).

<Raw materials>
(Thermoplastic resin)
-Ethylene / vinyl acetate copolymer: Mitsui / DuPont Polychemical Co., Ltd., trade name: Everflex EV220, hereinafter abbreviated as “EV220”.
-Refined candelilla wax: manufactured by Mitsuba Trading Co., Ltd., trade name: refined candelilla wax refinement, hereinafter abbreviated as "candelilla resin".
-Ethylene / ethyl acrylate / maleic anhydride copolymer: manufactured by Arkema Co., Ltd., trade name: Bondine HX8210, hereinafter abbreviated as “HX8210”.

(General-purpose nonionic surfactant)
・ Vinyl alcohol-based resin: manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Nichigo G polymer was used in a 50% aqueous solution (non-volatile content 50%, 7900 mPa · s (50 ° C., BM type, # 4, 12 rpm)). Hereinafter, it is abbreviated as “Nichigo G”.

(Polymer emulsifier raw material)
N, N-dimethylaminoethyl methacrylate: Sanyo Chemical Industries, Ltd., methacrylate DMA, hereinafter abbreviated as “DMA”.
・ Butyl methacrylate: Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “BMA”.
Lauryl methacrylate: manufactured by Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “SLMA”.
Isopropanol: Tokuyama Co., Ltd .: Tokuso IPA (registered trademark), hereinafter abbreviated as “IPA”.
• 2,2′-azobisisobutyronitrile: manufactured by Otsuka Chemical Co., Ltd., hereinafter abbreviated as “AIBN”.

(Production of polymer emulsifier 1)
A 150 L reactor equipped with a cooler, a nitrogen inlet tube, a stirrer, a dropping funnel and a heating / cooling jacket was charged with a predetermined amount of each component listed in Table 1, and after replacing with nitrogen, the internal temperature was increased to 80 ° C. Raised. Furthermore, the polymerization initiator AIBN in the amount shown in Table 1 was added to initiate the polymerization. The polymerization was continued for 4 hours while maintaining the temperature at 80 ° C. Next, the obtained copolymer was neutralized with the neutralizing agent in the amount shown in Table 1, and then replaced by adding water while distilling off the IPA, and a cationic polymer comprising an acrylic copolymer. A viscous aqueous solution of a neutralized product of an emulsifier was obtained (polymer emulsifier 1, yield: 97%, nonvolatile content: 35%, 5900 mPa · s (50 ° C., BH type, # 4, 12 rpm)).

(Production of polymer emulsifier 2)
Polymerization is carried out in the same manner as the polymer emulsifier 1 except that the raw material monomer, the polymerization initiator, the solvent and the neutralizing agent are changed to the types and amounts shown in Table 1, and an anionic property comprising an acrylic copolymer. A viscous aqueous solution of neutralized polymer emulsifier was obtained (polymer emulsifier 2, yield: 97%, nonvolatile content: 15%, 10000 mPa · s (50 ° C., BH type, # 4, 12 rpm)).

<Production of aqueous resin dispersion>
Example 1
Using a batch type kneader (BENCH KNEADER PBV-03, manufactured by Irie Trading Co., Ltd.) having a kneading disk rotating in a different direction, the ethylene / vinyl acetate copolymer (EV220) is kneaded and melted at 97 ° C., The polymer emulsifier 1 of 10 wt% with respect to the resin weight was divided into 90% and 10%, and charged from the same inlet. Divided input time was 4 minutes. After kneading, it was diluted with 95 ° C. ion exchange water to obtain a polyolefin resin aqueous dispersion having a nonvolatile content of 50%. Table 2 shows the division conditions and characteristics of the dispersion.

(Examples 2 to 4)
Kneading was carried out in the same manner as in Example 1 except that the polymer emulsifier was divided and added at the division ratio shown in Table 2, to obtain an aqueous polyolefin-based resin dispersion having a nonvolatile content of 50%. Table 2 shows the division conditions and characteristics of the dispersion.

(Example 5)
A polyolefin resin having a non-volatile content of 50% was kneaded in the same manner as in Example 1 except that a candelilla resin was used as the polymer emulsifier species and the polymer emulsifier was divided and added in the split ratio shown in Table 2. An aqueous dispersion was obtained. Table 2 shows the division conditions and characteristics of the dispersion.

(Example 6)
Except that HX8210 was used as the polymer emulsifier species and the polymer emulsifier was divided at the division ratio shown in Table 2, kneading was carried out in the same manner as in Example 1 to obtain an aqueous polyolefin-based resin dispersion having a nonvolatile content of 50%. It was. Table 2 shows the division conditions and characteristics of the dispersion.

(Comparative Example 1)
Kneading was carried out in the same manner as in Example 1 except that the entire amount was added all at once without dividing the polymer emulsifier, to obtain a polyolefin resin aqueous dispersion having a nonvolatile content of 50%. Table 2 shows the division conditions and characteristics of the dispersion.

(Comparative Example 2)
Kneading was carried out in the same manner as in Example 5 except that the entire amount was added all at once without dividing the polymer emulsifier to obtain an aqueous polyolefin-based resin dispersion having a nonvolatile content of 50%. Table 2 shows the division conditions and characteristics of the dispersion.

(Comparative Example 3)
Kneading was carried out in the same manner as in Example 6 except that Nichigo G was used as a polymer emulsifier seed and charged 100% at a time without being divided, thereby obtaining an aqueous polyolefin-based resin dispersion having a nonvolatile content of 50%. Table 2 shows the division conditions and characteristics of the dispersion.

(result)
As a result of the above, the aqueous thermoplastic resin dispersions obtained in Examples 1 to 6 had a small particle size of the emulsion particles, were transparent, had no fuzziness, and the emulsion was stable.
On the other hand, the aqueous thermoplastic resin dispersion obtained in Comparative Example 1 had a small particle size, but lacked stability of the emulsion, and agglomeration occurred when left for a while. Further, the aqueous thermoplastic resin dispersions obtained in Comparative Examples 2 to 3 had a large particle size and lacked emulsion stability.

11 Extruder 12 Hopper 13 (13a, 13b, 13c, 13d) Midway inlet 14 Outlet A Thermoplastic resin B (B1-B3) Polymer emulsifier C Hot water

Claims (8)

In a method for producing an aqueous dispersion of at least one thermoplastic resin selected from a polyolefin resin, a modified polyolefin resin, and an acrylic resin by a mechanical emulsification method,
As an emulsifier / dispersant, an aqueous solution or dispersion of a polymer emulsifier having a weight average molecular weight of 2,000 to 100,000 is used,
And while adding this polymeric emulsifier divided into several times , the 1st addition adds 50 weight% or more and 99 weight% or less of the total addition amount, and the addition after the 2nd is divided | segmented. A method for producing an aqueous dispersion of a thermoplastic resin, characterized in that it is added in equal amounts or divided so as to gradually decrease according to the number of times of addition . The mechanical emulsification method is performed using an extruder,
And the addition method of the said polymer emulsifier is performed from the inlet of the said extruder, The manufacturing method of the thermoplastic resin aqueous dispersion of Claim 1 characterized by the above-mentioned. The method for producing an aqueous thermoplastic resin dispersion according to claim 1 or 2 , wherein the first addition of the polymer emulsifier is performed in a kneading zone of an extruder. The viscosity of the aqueous solution or dispersion of the polymeric emulsifier, at a measurement temperature of 50 ° C., to any one of claims 1 to 3, equal to or less than 5,000 mPa · s or more 100,000 mPa · s The manufacturing method of the thermoplastic resin aqueous dispersion of description. The thermoplastic resin according to any one of claims 1 to 4 , wherein the concentration of the polymer emulsifier in the aqueous solution or dispersion of the polymer emulsifier is 5 wt% or more and 80 wt% or less. A method for producing an aqueous dispersion. The total amount of the polymeric emulsifier may be set, on the thermoplastic resin, a thermoplastic resin aqueous dispersion according to any one of claims 1 to 5, characterized in that 30 wt% or less than 3 wt% Liquid manufacturing method. The method for producing an aqueous thermoplastic resin dispersion according to any one of claims 1 to 6 , wherein the thermoplastic resin is a polyolefin resin or a modified polyolefin resin. The addition of the polymer emulsifier is carried out by setting the value η _R (η _resin / η _disp ) of the ratio of the viscosity of the resin in the extruder (η _resin ) and the viscosity of the polymer emulsifier (η _disp ) at the addition site to 0. The method for producing an aqueous thermoplastic resin dispersion according to claim 1 , wherein 1 <η _R <10.

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