JP2010209249A - Polymer emulsifier and resin dispersion using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat sealability at a low temperature of about 60-100°C and baking performance of a dry film produced from a thermoplastic resin dispersion obtained using a polymer emulsifier. <P>SOLUTION: The polymer emulsifier including a (meth)acrylic polymer having a midpoint temperature of 40-170°C by a flow tester 1/2 method and a weight-average molecular weight of 1,500-100,000 is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polymer emulsifier used for a dispersion of a thermoplastic resin having a dry film excellent in heat sealability and baking adhesion at low temperatures.

  In recent years, polyolefin resins such as polypropylene and polyethylene have been used for daily necessities, automotive parts, building materials and the like from the viewpoints of versatility, strength, physical properties, ease of molding, solvent resistance, and appearance.

  These polyolefin resins were difficult to bond due to the low polarity of the polyolefin resins themselves. Therefore, it is necessary to use an adhesion-imparting component such as chlorinated polyolefin dissolved in an organic solvent for the adhesion of these polyolefin resins.

  However, in recent years, there has been a strong demand for solvent-free paints for environmental protection and safety and health, and conventional solvent-based paints are being made water-based (see Patent Documents 1 and 2). In addition, it has been pointed out that chlorinated polyolefin resins may generate highly toxic dioxins when discarded by incineration.

  For example, in the case of an ethylene / vinyl acetate copolymer, the ethylene / vinyl acetate copolymer is first heated and melted, and then an anionic or nonionic emulsifier is added and stirred. Then, the method obtained by adding hot water and emulsifying using mechanical shear force, such as a homomixer, is mentioned (refer patent document 3).

  However, when the above-mentioned anionic emulsifier and nonionic emulsifier are used, there is a risk of bleeding out when the obtained product is used. On the other hand, a method for producing an aqueous resin dispersion using a neutralized product of a specific acrylic copolymer with improved emulsion stability as an anionic water-soluble polymer emulsifier is known (see Patent Document 4). ).

  However, this anionic water-soluble polymer emulsifier can improve the emulsion stability, but when water, a volatile base, etc. evaporate from the obtained resin dispersion, the carboxyl group in the polymer emulsifier Causes intramolecular or intermolecular association, resulting in an increase in melt viscosity and hindering the fusion of emulsion resin particles, resulting in poor film formation at low temperatures, and low temperature adhesion of the resulting dry film. In some cases, the transparency may be inferior, and its use may be limited.

  On the other hand, a method for producing a resin dispersion using a neutralized product of a specific acrylic copolymer having excellent low-temperature film-forming properties as a cationic water-soluble polymer emulsifier is known (see Patent Document 5).

  On the other hand, by using an anionic water-soluble polymer emulsifier into which polyalkylene glycol methacrylate is introduced, a method of suppressing the above-mentioned intramolecular or intermolecular association and decreasing the melt viscosity is known (patent) Reference 6)

Japanese Patent Laid-Open No. 06-336568 JP-A-11-106600 JP 57-61035 A JP 58-127752 A JP 58-118843 A JP-A-2-26631

  However, the emulsifiers described in Patent Documents 5 and 6 have insufficient heat sealability at a low temperature of about 60 to 100 ° C. In addition, the method described in Patent Document 5 has a problem that gelation may be caused depending on the blend of an anionic substance used for coating.

  Therefore, the invention about this polymer emulsifier solves such problems, and a dry film produced from a thermoplastic resin dispersion obtained by using this polymer emulsifier has a heat seal at a low temperature of about 60 to 100 ° C. It aims at improving the property and baking property.

  The present invention provides a polymer emulsifier containing a (meth) acrylic polymer having a weight average molecular weight of 1,500 to 100,000 and a midpoint temperature of 40 ° C. or more and 170 ° C. or less by a flow tester 1/2 method. By using it, the above-mentioned problem was solved.

  By emulsifying the thermoplastic resin using the polymer emulsifier according to the present invention, the heat sealability and baking property at a low temperature of about 60 to 100 ° C., the midpoint temperature by the flow tester 1/2 method exceeds 170 ° C. It is possible to exhibit a characteristic effect of improvement as compared with the case of using an emulsifier based on a polymer.

Schematic showing an example of a flow tester used to measure 1/2 method temperature Plunger drop-temperature curve

Hereinafter, the present invention will be described in detail.
The polymer emulsifier according to the present invention refers to an emulsifier containing a (meth) acrylic polymer which is a specific condition. In the present specification, “(meth) acryl” means “acryl or methacryl”. The said (meth) acrylic-type polymer means the polymer which has a (meth) acrylic-type monomer as a main component of a structural component. The term “main component” refers to occupying 50 mol% or more of the constituent components. Furthermore, you may have a vinyl-type monomer copolymerizable with this other than a (meth) acrylic-type monomer in the range which does not impair the effect of this invention.

  In addition, the total number of carbon atoms of the (meth) acrylic monomer used in the present invention is usually 3 to 50, preferably 3 to 30.

  The said (meth) acrylic-type monomer means the monomer which has a (meth) acryl group. Examples of the (meth) acrylic monomer include (meth) acrylic acid, (meth) acrylic acid alkyl ester monomer, amino group-containing (meth) acrylic monomer, amide group-containing (meth) acrylic monomer, hydroxyl group-containing ( Examples include (meth) acrylic monomers, sulfonic acid group-containing (meth) acrylic monomers, and other (meth) acrylic monomers. The “alkyl” group in the present invention includes straight-chain, branched-chain and alicyclic groups.

  The (meth) acrylic acid alkyl ester monomer is used as a component having a hydrophobic group to develop the emulsifying ability of the polymer emulsifier. Examples of such (meth) acrylic acid alkyl ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, (meth ) N-butyl acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, (meth ) Stearyl acrylate and the like. Moreover, in order to improve melt viscosity and emulsifying power, two or more of these components may be mixed and used.

  The amino group-containing (meth) acrylic monomer is a (meth) acrylic monomer such as aminoalkyl (meth) acrylate. Examples of the amino group-containing (meth) acrylic monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethyl (meth) acrylate. Amino-2-aminoethyl and the like can be mentioned.

  Examples of the amide group-containing (meth) acrylic monomer include (meth) acrylamide and N-substituted (meth) acrylamide in which one or both of the hydrogen atoms of the amide group are substituted with an alkyl group or the like. .

  These may use only 1 type and may mix and use 2 or more types. These amino group-containing (meth) acrylic monomers and amide group-containing (meth) acrylic monomers are used to adjust the melt viscosity and develop adhesion to a substrate.

  A typical example of the hydroxyl group-containing (meth) acrylic monomer is an alkyl ester monomer containing a hydroxyl group. Examples of the hydroxyl group-containing (meth) acrylic monomer include 2-hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, glycerin mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, and the like. . The (meth) acrylic acid hydroxyl group-substituted alkyl ester monomer is used to adjust the 1/2 method temperature described later.

  Examples of the vinyl monomer copolymerizable with the (meth) acrylic monomer include a carboxyl group-containing monomer and a styrene monomer. Examples of the carboxyl group-containing monomer include itaconic acid, citraconic acid, maleic acid, crotonic acid, fumaric acid, maleic acid monoalkyl ester, fumaric acid monoalkyl ester, and 2-methacryloyloxyethyl succinic acid. These carboxyl group-containing monomers are used to improve the emulsifying ability of the polymer emulsifier.

  A styrene monomer etc. are mentioned as said styrene-type monomer.

  If the (meth) acrylic polymer contains a monomer unit having a low glass transition temperature (Tg) among these monomer units, the 1/2 method temperature described later can be lowered. Specifically, the low glass transition temperature (Tg) means that the Tg is 80 ° C. or less, and preferably 50 ° C. or less. Examples of such a monomer having a low glass transition temperature (Tg) (hereinafter referred to as “low Tg monomer”) include 2-hydroxyethyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic acid. Examples include propyl, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, and lauryl (meth) acrylate. Among these, ethyl acrylate, 2-hydroxyethyl (meth) acrylate, and lauryl (meth) acrylate are particularly preferable.

[Content ratio of each component]
The said (meth) acrylic-type polymer means what contains 50 weight% or more of monomer units which consist of the said (meth) acrylic-type monomer with respect to all the monomer units in a polymer.

  Monomers containing a carboxyl group and / or a sulfonic acid group with respect to all monomer units contained in the (meth) acrylic polymer (hereinafter, sometimes collectively referred to as “carboxyl group-containing monomers”). 1% by weight or more is preferable. The presence of a monomer unit such as a carboxyl group can improve the emulsifying dispersibility of the resin. If it is less than 1% by weight, the emulsifying power may be insufficient. On the other hand, the carboxyl group-containing monomer is preferably 50% by weight or less. If it exceeds 50% by weight, the hydrophilicity becomes high and the balance as an emulsifier may be deteriorated. Examples of the carboxyl group-containing monomer include (meth) acrylic acid and the carboxyl group-containing monomer.

  The hydroxyl group-containing (meth) acrylic monomer is preferably contained in an amount of 1% by weight or more with respect to all monomer units contained in the (meth) acrylic polymer. Due to the presence of the monomer unit having a hydroxyl group, the melt viscosity at the time of forming the film tends to be low, and a uniform film tends to be easily formed. If it is less than 1% by weight, the coating film may be uneven, and the appearance may be poor. On the other hand, the hydroxyl group-containing (meth) acrylic monomer is preferably 70% by weight or less. When it exceeds 70% by weight, the hydrophilicity is increased, and the balance as an emulsifier may be deteriorated.

  Further, in order to set the “1/2 method temperature” described later in the following range, when the (meth) acrylic polymer has both a carboxyl group and / or a sulfonic acid group and a hydroxyl group, those groups The monomer so that the content ratio of the (meth) acrylic monomer unit having a weight ratio is the total amount of carboxyl group-containing units and / or sulfonic acid group-containing units / hydroxyl group-containing units = 1/70 to 50/1 Adjust the ratio. If it exceeds 50/1, the thermal fluidity may deteriorate and it may be difficult to lower the 1/2 method temperature. On the other hand, if it is less than 1/70, the hydrophilic group is insufficient and the emulsifying power may be reduced.

[Method for producing copolymer]
The (meth) acrylic polymer constituting the polymer emulsifier according to the present invention can be produced by the following method.
First, each component selected from the above monomers is weighed at a predetermined ratio. Next, each component is added separately to the polymerization vessel for polymerization, or each monomer is mixed in advance and then added to the polymerization vessel for copolymerization. Thereby, a copolymer can be manufactured.

  The above copolymerization is 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. This copolymerization is preferably carried out in the presence of a hydrophilic solvent such as ethanol, isopropanol or cellosolve or water.

  As the polymerization initiator, an initiator comprising a persulfate such as ammonium persulfate, potassium persulfate, sodium persulfate, etc., a redox initiator using the 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 Over 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.

  Moreover, when adjusting the 1/2 method temperature mentioned later to the said range by making the weight average molecular weight of the said (meth) acrylic-type polymer low, in order to adjust a polymerization degree, mercaptans, such as normal octyl mercaptan, etc. It is preferable to add a chain transfer agent such as α-methylstyrene, alkyl halide having 1 to 20 carbon atoms, preferably 3 to 10 carbon atoms. The amount of the chain transfer agent used may be adjusted according to the desired molecular weight, but is usually about 0.1 to 10% by weight with respect to the total amount of monomers.

[Neutralization of polymer]
The carboxyl group-containing monomer includes an acidic hydrophilic group such as a carboxyl group or a sulfonic acid group. When the (meth) acrylic polymer contains a carboxyl group-containing monomer, it is preferable that at least a part of the acidic hydrophilic group is neutralized with a basic substance. By neutralizing at least a part, the solubility in water is improved, the resin particle diameter in the resulting resin dispersion is reduced, and the dispersion state in water is stabilized. be able to.

  The degree of neutralization, that is, the degree of neutralization is preferably 50 mol% or more, and preferably 60 mol% or more. If it is less than 50 mol%, the solubility of the resulting copolymer in water tends to be insufficient. On the other hand, the upper limit of the degree of neutralization is preferably 200 mol%, and preferably 150 mol%. When it is larger than 200 mol%, the water resistance tends to be insufficient.

  Examples of the basic substance include basic compounds such as alkali metal and alkaline earth metal hydroxides, ammonia, alkylamines, alkanolamines, morpholine, and the like. Examples of the alkali metal or alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, magnesium hydroxide and the like, and specific examples of alkylamines include methylamine, dimethylamine, trimethylamine, ethylamine, Examples include diethylamine, and specific examples of alkanolamines include 2-amino-2-methylpropanol. Among these, it is preferable to use ammonia or trimethylamine having volatility during low-temperature drying because the water resistance of the resulting film can be improved. Moreover, in order to improve emulsifying power, sodium hydroxide and potassium hydroxide are preferable.

  The neutralization reaction is performed by reacting the (meth) acrylic polymer and the basic compound at 20 to 100 ° C. for 0.1 to 3 hours. In addition, a monomer containing a carboxyl group or the like may be previously neutralized with a basic compound and used for copolymerization.

[Features of (meth) acrylic polymer]
The melt viscosity of the (meth) acrylic polymer is 40 ° C. at a midpoint temperature (hereinafter referred to as “1/2 method temperature”) measured by a melt viscosity measurement using a flow tester, that is, a flow tester 1/2 method. It is necessary to be above, preferably 50 ° C. or higher, and more preferably 60 ° C. or higher. If it is lower than 40 ° C., the dry film of the polymer emulsifier tends to be sticky and sticky (blocking). On the other hand, the ½ method temperature needs to be 170 ° C. or lower, preferably 140 ° C. or lower, and more preferably 130 ° C. or lower. This is because when the temperature exceeds 170 ° C., a difference from a polymer used for a conventional emulsifier having poor heat sealability at a low temperature hardly appears.

  In addition, the specific measurement of said 1/2 method temperature is possible by the following procedures. As the flow tester, the elevated flow tester shown in FIG. 1 can be used. This comprises a vertically standing cylinder 2, a plunger (piston) that can move up and down in the cylinder 2, a die 4 disposed at the lower end of the cylinder 2, and a die presser 5 that fixes the die 4. .

  First, the above-mentioned weighed sample 3 is placed in the cylinder 2 and the plunger 1 is inserted into the cylinder 2. Next, a load P is applied to the upper part of the plunger 1 and heated at a constant temperature increase rate.

  Then, the temperature and the descending amount of the plunger 1 were measured, and the relationship between the two was graphed. The result is as shown in the plunger drop-temperature curve (flow tester outflow curve) in FIG. In FIG. 2, the temperature at the time when the sample 3 flows out from the nozzle of the die 4 is defined as an outflow start point (flow start temperature), and the height between the outflow start point and the highest point of the obtained S-shaped curve. When h is h, the temperature at h / 2 is the ½ method temperature.

  The weight average molecular weight of the (meth) acrylic polymer needs to be 1,500 or more, preferably 2,000 or more. If it is less than 1,500, stickiness may occur after coating. On the other hand, it is necessary to be 100,000 or less, and preferably 60,000 or less. When it exceeds 100,000, the melt viscosity becomes high, and the low-temperature heat sealability may be deteriorated or baking may be poor.

  The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably −10 ° C. or higher, and more preferably 0 ° C. or higher. If it is less than −10 ° C., stickiness tends to occur after coating, and blocking tends to occur. On the other hand, it is preferably 100 ° C. or lower, and more preferably 90 ° C. or lower.

  In addition, said glass transition temperature (Tg) is based on the value measured by the temperature rising temperature of 10 degree-C / min by the differential scanning calorimetry (DSC) based on JISK7121.

[Use as polymer emulsifier]
The above (meth) acrylic polymer obtained by the above method is used as it is or within a range not inhibiting the effects of the present invention, an antifungal agent, an antioxidant, a UV absorber, and an adhesive for improving adhesion. It becomes a polymer emulsifier by adding additives such as an agent (tackifier, wax, etc.).

  This polymer emulsifier can be used as an emulsifier for emulsifying and dispersing a thermoplastic resin to obtain a resin dispersion. When this resin dispersion is formed into a film, low temperature heat sealability, bakeability, and surface smoothness are obtained. Becomes easy to obtain a good dry film. Further, it can be used as a compatibilizing agent in kneading two or more kinds of polymer substances.

  As such a thermoplastic resin, a general thermoplastic resin such as a polyolefin resin, an ethylene-vinyl acetate copolymer resin, a polyester resin, or a polystyrene resin can be used. The thermoplastic resin may be a single resin or a mixture. For example, by using the polymer emulsifier according to the present invention, the thermoplastic resin can be emulsified to obtain a dispersion. This thermoplastic resin dispersion has good affinity with the corresponding thermoplastic resin species, and can be used as an adhesive, pressure-sensitive adhesive, or coating agent for the resin.

  These thermoplastic resins are substances that are conventionally difficult to make into an aqueous dispersion, and are usually used by being dissolved in an organic solvent. Such a solution is highly effective as an adhesive for polypropylene resins, ethylene-vinyl acetate copolymer resins, and polystyrene resins, but by using the above polymer emulsifier, it becomes possible to remove the solvent, It becomes possible to manufacture an adhesive for resin with a small environmental load.

  Further, depending on the solvent, the resin of the adherend may be dissolved. Depending on the type of the solvent used, the application may be limited, but such a problem does not occur in the dispersion of the present invention. .

  As a method for producing a resin dispersion by emulsifying and dispersing the above thermoplastic resin using the polymer emulsifier of the present invention, at least one of these molten thermoplastic resins is used as the above polymer emulsifier or Examples thereof include a method of adding to a water containing a Japanese product and mixing and dispersing by applying a mechanical shearing force using a homomixer, a Banbury mixer, a kneader, an extruder or the like. The most preferable embodiment uses a multi-screw extruder having two or more screws in the casing, continuously supplies the thermoplastic resin from the hopper of the multi-screw extruder or a midway supply port, and heats and melts it. Kneading, and further supplying an aqueous solution containing the polymer emulsifier or a neutralized product thereof under pressure from at least one supply port provided in the compression zone, metering zone, and degassing zone of the multi-screw extruder, By kneading this and the above-mentioned heat-melted resin with a screw, the resin dispersion can be continuously produced from the die.

  The blending ratio of the thermoplastic resin and the polymer emulsifier (in terms of solid content) is 0.1 parts by weight or more, preferably 1 part by weight or more of the polymer emulsifier with respect to 100 parts by weight of the thermoplastic resin. Good. On the other hand, the upper limit of the blending ratio of the polymer emulsifier is 20 parts by weight, preferably 15 parts by weight. If the blending amount of the polymer emulsifier is less than 0.1 parts by weight, the emulsification is insufficient and the resin may be separated and settled. On the other hand, when the blending ratio of the polymer emulsifier exceeds 20 parts by weight, the water resistance of a molded article such as a film obtained from the resin dispersion may deteriorate, or the dispersed resin may cause secondary aggregation.

  The amount of water used is preferably used so that the solid concentration of the obtained resin dispersion is 20 to 65% by weight. The obtained resin dispersion is blended with an antifoaming agent, a viscosity modifier, an anionic or nonionic surfactant, an antioxidant, an antiseptic, an ultraviolet absorber, a tackifier, and the like. May be.

  The resin dispersion produced in this manner is a water dispersion in which the above resin particles have an average volume particle size of 5 μm or less and a particle size of 1 μm or less of 10% by weight or more, preferably 20% by weight or more. The viscosity at 25 ° C. is 10 to 10,000 mPa · s, preferably 50 to 5,000 mPa · s. A more preferable viscosity is 50 to 2,000 mPa · s.

  The resin dispersion can be used as a paint, a pressure-sensitive adhesive, an ink binder, an adhesive, or an emulsion modifier, depending on the type of resin used.

  Hereinafter, the present invention will be described more specifically with reference to examples. First, the evaluation method and the raw materials used will be described.

<Evaluation method>
[Non-volatile content]
About 1 g of the polymer emulsifier sample obtained in each production example or various emulsion samples obtained in the examples and comparative examples are precisely weighed and dried in a hot air circulating dryer at 105 ° C. for 3 hours, and then released in a desiccator. It was cooled and its weight was measured. The nonvolatile content was calculated according to the following formula.
Nonvolatile content [%] = (weight of sample after drying / weight of sample before drying) × 100

[Measurement of weight average molecular weight (Mw) by GPC]
The sample was dried at room temperature for 24 hours, dried at room temperature under reduced pressure (using a vacuum dryer LHV-122 (manufactured by Tabai Espec Co., Ltd.)) for 5 hours or more, added chloroform and methanol, and then an esterifying agent (trimethylsilyldiazomethane). The hexane solution was stirred at room temperature until allowed to dissolve (48-72 hours). Then, it was made to dry at room temperature.
The dried sample was adjusted to 0.2% with tetrahydrofuran (THF) and used as a sample.
The sample was measured under the following conditions using Shimadzu Corporation GPC-6A.
・ Flow rate: 1 ml / min
Column: PL gel 10 μm mix B (manufactured by Polymer Laboratories)
Standard sample: monodispersed PS (manufactured by Polymer Laboratories)
Reference: Sumilizer BHT (manufactured by Sumitomo Chemical Co., Ltd.)
・ Detector: RI, UV

[Measurement of glass transition temperature Tg]
Using a DSC manufactured by SII, measurement was performed at a temperature elevation temperature of 10 ° C./min by differential scanning calorimetry (DSC) based on JIS K7121.

[Melting temperature (1/2 method temperature)]
The polymer emulsifier sample obtained in each production example was allowed to stand at room temperature for 24 hours, and then vacuum dried at room temperature for 5 hours. About 1 g of this was weighed and used as a sample, and an elevated structure having the structure shown in FIG. The flow tester 1/2 method temperature was measured using a type flow tester (manufactured by Shimadzu Corporation: CFT-500). Area A of the front end surface of the plunger 1 in the cylinder 2 is 1 cm ^2, The nozzle provided in the die 4 (discharge hole), the diameter 1 mm, a length of 1 mm. The load P was 10 kgf, and heating was performed at a temperature increase start temperature of 40 ° C. and a temperature increase rate of 6.0 ° C./min.

[Particle size]
Made by Shimadzu Corporation: The volume particle size was measured using a laser diffraction particle size distribution analyzer (SALD2000).

<Raw materials>
[Monomer containing a carboxyl group]
Acrylic acid: manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as “AA”.
Methacrylic acid: Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “MAA”.

[(Meth) acrylic acid alkyl ester monomer]
・ Methyl methacrylate: manufactured by Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “MMA”.
-Lauryl methacrylate: Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “SLMA”.

[Low Tg monomer]
-2-hydroxyethyl acrylate: abbreviated as "HEA" manufactured by Nippon Shokubai Co., Ltd.
-Ethyl acrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as “EA”.
[Chain transfer agent]
Normal octyl mercaptan: Wako Pure Chemical Industries, Ltd., hereinafter abbreviated as “NOM”.

[solvent]
Isopropyl alcohol: manufactured by Tokuyama Corporation, hereinafter abbreviated as “IPA”.

[resin]
-Ethylene-vinyl acetate copolymer resin: made by Mitsui DuPont Polychemical Co., Ltd .: EVA220V, hereinafter abbreviated as "EVA".
-Tack Fire: Arakawa Chemical Industries, Ltd .: Petroleum resin These were mixed at a weight mixing ratio EVA / Tack Fire = 9/1.

<Heat seal and strength measurement>
A resin dispersion prepared by using the polymer emulsifier obtained in each Example and Comparative Example was applied to a film made of polyethylene terephthalate (PET) having a thickness of 25 μm so as to be 4 g / m ^2, and 20 ° C. at 20 ° C. The sample was prepared by drying for 2 seconds.
The coated surfaces of this sample were heat-sealed with a heat sealer at a predetermined temperature for 1 ^{second at} a pressure of ² kg / cm ² . The obtained sample was cut into a 15 mm width strip, and the seal strength when peeled at a rate of 200 mm / min was measured using a tensile tester (autostrain). Further, the percentage of the heat seal strength at each temperature when the heat seal strength at 140 ° C. was taken as 100% was calculated.

<Low temperature seizure>
A resin dispersion liquid was applied to a polyethylene terephthalate (PET) film having a thickness of 25 μm so that the coating amount was 10 g / cm ² and dried at 80 ° C. for 5 minutes. About the obtained coating film, adhesiveness was evaluated by the following reference | standard by the cellophane tape peeling test.
○: No peeling of coating film ×: Peeling of coating film

(Examples 1 to 3, Comparative Example 1)
<Production of (meth) acrylic polymer (polymer emulsifier)>
In a four-necked flask (reactor) equipped with a reflux condenser, a nitrogen inlet tube, a stirrer, and a thermometer, 150 parts by weight of isopropanol (IPA), various monomers shown in Table 1, and Examples 1 and 2 A chain transfer agent was charged, and the reactor was purged with nitrogen. Then, 2,2′-azobisisobutyronitrile (manufactured by Otsuka Chemical Co., Ltd., hereinafter abbreviated as “AIBN”) 0.6 part by weight was added, Polymerization was carried out at 80 ° C. for 3 hours.
Next, the mixture was neutralized with a 25% aqueous ammonia solution so as to correspond to the neutralization degree shown in Table 1 corresponding to the total amount of AA and MAA, and finally a viscous ( An aqueous solution of a neutralized product of a (meth) acrylic polymer was obtained. (Yield 97%).

<Manufacture of resin dispersion>
110 parts by weight of a 9: 1 weight ratio of EVA and tackifier resin mixture is mixed and melted at 140 ° C. in a non-rotating non-meshing biaxial kneader (Irie Shokai Co., Ltd .: PBV-03). I let you. To this, the above polymer emulsifier is added as a solid content so as to be 5 parts by weight of the polymer emulsifier per 100 parts by weight of the resin mixture, mixed for 5 minutes, and then added with 110 parts by weight of ion-exchanged water. Mixing for a minute gave a milky white resin dispersion.

<Result>
In Example 1, compared to Comparative Example 1 in which the molecular weight was not lowered with a chain transfer agent, the 1/2 method temperature was lowered and the heat seal strength in the vicinity of 80 to 100 ° C. was improved.

  In Example 2 in which half of the MMA in Example 1 was changed to a low Tg monomer, the heat seal strength was slightly reduced as compared with Example 1, but compared with Comparative Example 1, the heat seal in the vicinity of 80 to 100 ° C. Strength improved.

  In Example 2, the weight average molecular weight is assumed to be high without adding a chain transfer agent, while in Example 3 in which MMA used in Example 2 is changed to EA which is a low Tg monomer, the temperature is 80 to 100 ° C. The heat seal strength at a low temperature was higher than that of Comparative Example 1, and a substantially constant heat seal strength could be obtained from 60 to 140 ° C.

1 Plunger 2 Cylinder 3 Sample 4 Die 5 Die presser

Claims (8)

  A (meth) acrylic polymer having a midpoint temperature of 40 ° C. or higher and 170 ° C. or lower by a flow tester 1/2 method is included, and the weight average molecular weight of the (meth) acrylic polymer is 1500 to 100,000. Some polymer emulsifiers.   The polymer emulsifier according to claim 1, wherein the (meth) acrylic polymer has a glass transition temperature Tg of from -10 ° C to 100 ° C.   The polymer emulsifier according to claim 1 or 2, comprising 1 to 50% by weight of a monomer unit having a carboxyl group based on all monomer units contained in the (meth) acrylic polymer.   The polymeric emulsifier according to claim 1 or 2, comprising 1 to 70% by weight of monomer units having a hydroxyl group with respect to all monomer units contained in the (meth) acrylic polymer.   The (meth) acrylic polymer has a carboxyl group and a hydroxyl group as functional groups, and the content ratio thereof is such that the content ratio of the structural units having these groups is carboxyl group / hydroxyl group = 1. The polymer emulsifier according to any one of claims 1 to 4, which is / 70 to 50/1.   A resin dispersion obtained by emulsifying and dispersing a thermoplastic resin using the polymer emulsifier according to any one of claims 1 to 5.   The resin dispersion according to claim 6, wherein the thermoplastic resin is at least one of a polyolefin resin, an ethylene-vinyl acetate copolymer resin, a polyester resin, and a styrene resin.   The molten thermoplastic resin is added to water containing the polymer emulsifier according to any one of claims 1 to 5 or a neutralized product thereof, and mixed and dispersed by applying a mechanical shearing force. A method for producing a resin dispersion obtained by emulsifying and dispersing a thermoplastic resin.

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