JP6073733B2 - Method for producing aqueous emulsion adhesive - Google Patents

Description

  The present invention relates to an aqueous emulsion adhesive and a method for producing the same.

  Conventionally, as an adhesive for building materials, processed paper, water-repellent corrugated cardboard, etc., an adhesive mainly composed of a polyvinyl acetate emulsion is preferably used, but for the purpose of improving adhesiveness particularly at low temperatures, An organic solvent which is not preferable for the environment and human body such as xylene is contained. Therefore, as a technology that does not contain these organic solvents, a plastic overlay containing polyvinyl acetate emulsion and aqueous polyurethane emulsion as essential components and containing at least one of dimethyl adipate, dimethyl succinate, and dimethyl glutarate Adhesives are disclosed (see JP-A-11-209722), but the low-temperature adhesiveness may be insufficient.

  Therefore, as a water-based adhesive that improves low-temperature adhesiveness without adding toluene or the like, and has heat resistance and low odor, an ethylene-vinyl acetate copolymer emulsion has low-temperature adhesiveness. As an improving agent, one having a specific amount of at least one selected from dimethyl adipate, dimethyl glutarate, and dimethyl succinate has been proposed (see JP-A No. 2002-121518).

  However, it is difficult to say that the conventional adhesives sufficiently satisfy the market demand for low temperature adhesion, heat resistance and low odor, and improvements are desired.

JP-A-11-209722 JP 2002-121518 A

  This invention is made | formed based on the above-mentioned situation, and it aims at provision of the adhesive agent which is excellent in low temperature adhesiveness and heat resistance, and is low odor.

The invention made to solve the above problems is
A vinyl acetate (co) polymer (A), a branched alkyl group having 7 to 29 carbon atoms or a branched alkoxy group having 7 to 29 carbon atoms (R ¹ ), a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, Surfactant (B) having a group (X ¹ ) selected from a phosphoric acid group or a salt thereof, a sulfuric acid group or a salt thereof, and a polyoxyalkylene group
An aqueous emulsion containing
The content of the surfactant (B) with respect to 100 parts by mass of the vinyl acetate (co) polymer (A) is an aqueous emulsion adhesive having a content of 0.1 to 30 parts by mass.

The water-based emulsion-type adhesive contains a specific amount of the surfactant (B) having the above specific structure in the water-based emulsion, so that it is excellent in low-temperature adhesiveness and heat resistance and has a low odor. The reason why the above-described effect is achieved when the aqueous emulsion of the aqueous emulsion adhesive contains the specific surfactant (B) is not necessarily clear, but is presumed as follows, for example. That is, the surfactant (B) has hydrophobic R ¹ and hydrophilic X ¹ . Since the hydrophobic R ¹ is the specific branched alkyl group or branched alkoxy group, the wettability of the dispersoid vinyl acetate (co) polymer (A) to the base material can be appropriately controlled. . As a result, the water-based emulsion adhesive is considered to be excellent in low-temperature adhesiveness and heat resistance. Further, the aqueous emulsion adhesive does not contain an organic solvent such as toluene, so that it can have a low odor.

  It is preferable that the aqueous emulsion adhesive further contains polyvinyl alcohol (C). Polyvinyl alcohol (C) is considered to function as a polymerization stabilizer or a post-treatment agent after polymerization. As a result, the water-based emulsion adhesive is superior in low-temperature adhesiveness and heat resistance and has a lower odor. Can do.

The method for producing the aqueous emulsion adhesive of the present invention comprises:
Using polyvinyl alcohol (C) as a polymerization stabilizer to obtain an aqueous emulsion containing a vinyl acetate (co) polymer (A) by (co) polymerization of a monomer containing vinyl acetate in an aqueous medium; and Adding a surfactant (B) to the aqueous emulsion.

  According to the method for producing an aqueous emulsion adhesive of the present invention, a vinyl acetate (co) polymer (C) is used as a polymerization stabilizer by polymerization of a monomer containing vinyl acetate in an aqueous medium. An aqueous emulsion containing A) is obtained, and a surfactant (B) is added to the aqueous emulsion to easily and reliably produce an aqueous emulsion adhesive having excellent low-temperature adhesion and heat resistance and low odor. Can do.

It is preferable to further include a step of adding polyvinyl alcohol (C) to the aqueous emulsion.

  According to the production method, by adding polyvinyl alcohol (C) as a post-adding treatment agent to the aqueous emulsion, it is easy to obtain a low-odor aqueous emulsion adhesive with excellent low-temperature adhesion and heat resistance. It can be manufactured reliably.

  As described above, the aqueous emulsion adhesive of the present invention is excellent in low-temperature adhesiveness and heat resistance and has a low odor. Therefore, the aqueous emulsion adhesive of the present invention is not limited to adhesives for wood and plastic, paper and plastic, inorganic material and plastic, metal and paper, etc., but is also suitable for woodworking, paper packaging, general use, etc. Used for.

<Water-based emulsion type adhesive>
The aqueous emulsion adhesive of the present invention contains a vinyl acetate (co) polymer (A) and a surfactant (B) as essential components. The aqueous emulsion adhesive preferably contains polyvinyl alcohol (C). Hereinafter, each component will be described in detail.

<Vinyl acetate (co) polymer (A)>
The vinyl acetate (co) polymer (A) is obtained by (co) polymerizing a monomer containing vinyl acetate in an aqueous medium. As the monomer containing vinyl acetate, vinyl acetate alone, a combination of ethylene and vinyl acetate, or a combination of vinyl acetate and (meth) acrylic ester, wherein vinyl acetate is 60% by mass or more preferable. The aqueous emulsion of the aqueous emulsion adhesive contains the vinyl acetate (co) polymer (A) as a dispersoid.

<Surfactant (B)>
The surfactant (B) includes a branched alkyl group having 7 to 29 carbon atoms or a branched alkoxy group having 7 to 29 carbon atoms (R ¹ ), a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or It is a surfactant having a group (X ¹ ) selected from a salt thereof, a sulfate group or a salt thereof, and a polyoxyalkylene group.
The surfactant (B) has hydrophobic R ¹ and hydrophilic X ¹ . Since the hydrophobic R ¹ is the specific branched alkyl group or branched alkoxy group, the aqueous emulsion adhesive has excellent low-temperature adhesiveness and heat resistance and low odor.

X ¹ is preferably a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a sulfuric acid group or a salt thereof, or a polyoxyalkylene group, more preferably a salt of a sulfonic acid group, a sulfuric acid group or a salt thereof, or a polyoxyalkylene group. preferable. Examples of the counter cation in each of the above salts include alkali metal cations such as sodium and potassium; alkaline earth metal cations such as calcium and barium; ammonium ions and the like. Among these, sodium cations are preferable from the viewpoint of availability. It said X ¹ is, that it is such a specific group, the aqueous emulsion adhesive can be a lower odor with excellent low-temperature adhesiveness and heat resistance.

Examples of the branched alkyl group having 7 to 29 carbon atoms represented by R ¹ include a 2-ethylhexyl group, a 2-hexyloctyl group, and a 2-hexyldecyl group.
Examples of the branched alkoxy group having 7 to 29 carbon atoms represented by R ¹ include a 2-ethylhexyloxy group, a 2-hexyloctyloxy group, and a 2-hexyldecyloxy group.

The number of carbon atoms of the ^{R 1,} preferably from 7 to 24, more preferably from 7 to 20, more preferably 8 to 18, 12 to 18 are particularly preferred. By setting the carbon number of R ¹ within the above range, the water-based emulsion adhesive can have a low odor while being excellent in low-temperature adhesiveness and heat resistance.

When the surfactant (B) has one each of R ¹ and X ¹ , the surfactant (B) is preferably a compound represented by R ¹ -X ¹ .

When the surfactant (B) has a plurality of R ¹ or X ¹ , the surfactant (B) can have those linking groups (R ′). Examples of the linking group include a chain hydrocarbon group, an aromatic hydrocarbon group, an ester group, and a group obtained by combining these. As carbon number of the said coupling group, 1-20 are preferable and 1-10 are more preferable.

  As the surfactant (B), sodium 2-ethylhexyl sulfate, polyoxyethylene 2-ethylhexyl ether, and sodium di-2-ethylhexyl sulfosuccinate are preferable.

  The content of the surfactant (B) needs to be 0.1 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the vinyl acetate (co) polymer (A). The amount is more preferably no less than 20 parts by mass and no greater than 0.2 parts by mass. By making content of surfactant (B) into the said range, the said water-based emulsion type adhesive can be made more low-odor while being excellent by low-temperature adhesiveness and heat resistance.

<Polyvinyl alcohol (C)>
As polyvinyl alcohol (C), polyvinyl alcohol (C1) used as a polymerization stabilizer in the (co) polymerization of a monomer containing vinyl acetate in an aqueous medium, and an aqueous medium of a monomer containing vinyl acetate Examples thereof include polyvinyl alcohol (C2) which is added later to an aqueous emulsion obtained by (co) polymerization therein. Polyvinyl alcohol (C1) and polyvinyl alcohol (C2) may be used alone or in combination, but are preferably used in combination.

The polyvinyl alcohol (C) may be a polymer (unmodified PVA) of vinyl alcohol units (—CH ₂ —CHOH—), or a copolymer of this vinyl alcohol unit and other monomer units ( Modified PVA). Examples of the other monomer units include monomer units having an alkyl group, an alkenyl group, an unsaturated aliphatic carboxylic acid, and an acetoacetyl group. The content of the other monomer units is preferably 0.05 mol% or more and 5 mol% or less, and more preferably 0.1 mol% or more and 2 mol% or less.

The content rate of said other monomer unit can be calculated | required from the proton NMR of the modified vinyl ester-type polymer which is a precursor of the said polyvinyl alcohol (C). Specifically, after reprecipitation purification of the modified vinyl ester polymer with n-hexane / acetone three times or more sufficiently, drying is performed under reduced pressure at 50 ° C. for 2 days to prepare a sample for analysis. . This sample is dissolved in CDCl ₃ and measured at room temperature using 500 MHz proton NMR (JEOL GX-500).

  The viscosity average degree of polymerization of the polyvinyl alcohol (C) is preferably from 100 to 5,000, more preferably from 500 to 4,000, still more preferably from 700 to 3,000. The viscosity average degree of polymerization may be simply referred to as the degree of polymerization. When this polymerization degree exceeds 5,000, there exists a possibility that productivity of polyvinyl alcohol (C) may fall.

This viscosity average degree of polymerization (P) is measured according to JIS-K6726: 1994. That is, after re-saponifying and purifying polyvinyl alcohol (C), it is obtained from the intrinsic viscosity [η] (unit: deciliter / g) measured in water at 30 ° C. by the following formula.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

  The saponification degree of the polyvinyl alcohol (C) is preferably 20 mol% or more and 99.99 mol% or less, more preferably 40 mol% or more and 99.95 mol% or less, and further preferably 70 mol% or more and 99.9 mol% or less. . When this saponification degree is less than 20 mol%, the water solubility of polyvinyl alcohol (C) falls, As a result, preparation of the said aqueous emulsion may become difficult. On the contrary, if the degree of saponification exceeds 99.99 mol%, it is not practical because the production of polyvinyl alcohol (C) becomes difficult. The saponification degree of the alkyl-modified PVA is measured according to JIS-K6726: 1994.

<Method for producing polyvinyl alcohol (C)>
Although it does not specifically limit as a manufacturing method of polyvinyl alcohol (C), Polyvinyl alcohol is obtained by saponifying polyvinyl acetate obtained by superposing | polymerizing vinyl acetate conventionally, for example. A copolymer (modified PVA) of a vinyl alcohol unit and another monomer unit is obtained by, for example, copolymerizing a vinyl ester monomer and the above other monomer unit to obtain a copolymer (vinyl). It can be obtained by saponifying an ester polymer.

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate and the like. Can be mentioned. Among these, vinyl acetate is preferable.

In addition, in the copolymerization of the other monomer and the vinyl ester monomer, chain transfer is performed within the range not impairing the gist of the present invention for the purpose of adjusting the degree of polymerization of the copolymer obtained. An agent may be added. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde;
Ketones such as acetone and methyl ethyl ketone;
Mercaptans such as 2-hydroxyethanethiol;
Halogenated hydrocarbons such as trichlorethylene and perchlorethylene;
And phosphinic acid salts such as sodium phosphinate monohydrate. Of these, aldehydes and ketones are preferable.

  The amount of the chain transfer agent to be added can be determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target vinyl ester polymer, and thus the degree of polymerization of PVA. 0.1 mass% or more and 10 mass% or less are preferable with respect to a system monomer.

  The temperature employed when copolymerizing the other monomer and the vinyl ester monomer is preferably 0 ° C to 200 ° C, more preferably 30 ° C to 140 ° C. When the copolymerization temperature is lower than 0 ° C., it is difficult to obtain a sufficient polymerization rate. As a method for controlling the temperature employed in the copolymerization to 0 ° C. to 200 ° C., for example, by controlling the polymerization rate, the heat generated by the polymerization reaction and the heat radiation from the surface of the reactor are balanced. And a method of controlling by an external jacket using an appropriate heat medium. Among these methods, the method of controlling by an external jacket using an appropriate heat medium is preferable from the viewpoint of safety.

  Examples of the polymerization method used for the copolymerization of the other monomer and the vinyl ester monomer include batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. As the polymerization method, known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be used. Among these, a bulk polymerization method in which polymerization is performed in a solvent-free or alcohol-based solvent or a solution polymerization method is preferably employed, and an emulsion polymerization method is employed for the purpose of producing a copolymer having a high degree of polymerization. .

  Examples of the alcohol solvent include methanol, ethanol, n-propanol, and the like, but are not limited thereto. These solvents can be used as a mixture of two or more.

  As an initiator used for the copolymerization of the other monomer and the vinyl ester monomer, conventionally known azo initiators, peroxide initiators, redox initiators are used depending on the polymerization method. An agent or the like can be used.

  Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2, 4-dimethylvaleronitrile) and the like.

Examples of the peroxide-based initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate;
Perester compounds such as t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, t-butyl peroxydecane;
Examples thereof include acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and the like. Furthermore, the initiator can be combined with potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like to form an initiator.

  Examples of the redox initiator include a combination of the above peroxide and a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, Rongalite, and the like.

  In addition, when copolymerization with the said other monomer and the said vinyl ester-type monomer is performed at high temperature, coloring of PVA etc. resulting from decomposition | disassembly of a vinyl ester-type monomer may be seen. In this case, it is preferable to add an antioxidant such as tartaric acid to the polymerization system in an amount of about 1 to 100 ppm based on the vinyl ester monomer for the purpose of preventing coloring.

  For the saponification reaction of the modified vinyl ester copolymer obtained by the above copolymerization, a known basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as p-toluenesulfonic acid is used. Alcohololysis reactions or hydrolysis reactions that have been applied can be applied.

  Examples of the solvent that can be used in the saponification reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene. It is done. In addition, these solvents can be used individually or in combination of 2 or more types.

  As the saponification reaction, a method of using methanol or a methanol / methyl acetate mixed solution as a solvent and sodium hydroxide as a catalyst is simple and preferable.

<Other ingredients>
The aqueous emulsion type adhesive may be an emulsion itself obtained by polymerization, and may contain a crosslinking agent, a filler, a plasticizer and the like.

  The aqueous emulsion adhesive of the present invention usually contains a dispersion medium such as water in addition to the vinyl acetate (co) polymer (A) and the surfactant (B) described above.

<Method for producing aqueous emulsion adhesive>
The method for producing the aqueous emulsion adhesive is as follows:
Using polyvinyl alcohol (C) as a polymerization stabilizer to obtain an aqueous emulsion containing a vinyl acetate (co) polymer (A) by (co) polymerization of a monomer containing vinyl acetate in an aqueous medium; and Step 2 of adding a surfactant (B) to the aqueous emulsion obtained in Step 1 above
Have

(Process 1)
In this step, for example, polyvinyl alcohol (C) is used by temporarily or continuously adding a monomer containing vinyl acetate in the presence of a conventionally known polymerization initiator. Although it does not restrict | limit especially as the usage-amount of the said polyvinyl alcohol (C), It is 1-25 mass parts normally with respect to 100 mass parts of vinyl acetate (co) polymers (A) which are the above-mentioned dispersoid, 15 parts by mass is preferred.

(Process 2)
In this step, the above-mentioned surfactant (B) is added to the aqueous emulsion obtained in Step 1. The content of the surfactant (B) needs to be 0.1 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the vinyl acetate (co) polymer (A). The amount is more preferably no less than 20 parts by mass and no greater than 0.2 parts by mass. By making content of surfactant (B) into the said specific range, the aqueous emulsion type adhesive obtained can be made into low odor while being excellent by low temperature adhesiveness and heat resistance.

(Process 3)
In addition, the method for producing the water-based emulsion adhesive is as follows:
Step 3 of adding polyvinyl alcohol (C) to the aqueous emulsion obtained in Step 2 above
It is preferable to further have.

  Thus, the aqueous emulsion adhesive can also be obtained by adding polyvinyl alcohol (C) as a post-addition treatment agent to the aqueous emulsion obtained in Step 2. Although it does not specifically limit as addition amount in the case of adding polyvinyl alcohol (C) as a post-addition processing agent, Polyvinyl alcohol (C) solid content will be 0-20 mass parts with respect to 100 mass parts of emulsion solid content. It is preferable to add to 1 part by mass, and 1 part by mass to 10 parts by mass is more preferable.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples. In the following examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

  The physical properties of PVA (non-modified PVA and modified PVA) used in the following examples and comparative examples were measured according to the following method.

[Modification rate]
The modification rate of each PVA (the content of monomer units having an alkyl group in PVA) was determined by the method using proton NMR described above.

[Degree of polymerization]
The viscosity average degree of polymerization of each PVA was determined by the method described in JIS-K6726: 1994.

[Saponification degree]
The degree of saponification of each PVA was determined by the method described in JIS-K6726: 1994.

<Manufacture of PVA>
[Production Example 1] (Production of PVA1)
Into a 3 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube and initiator addition port, 1180 g of vinyl acetate and 820 g of methanol were charged, and the inside of the system was purged with nitrogen for 30 minutes while bubbling nitrogen. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.79 g of 2,2′-azobisisobutyronitrile (AIBN) was added to start polymerization, and polymerization was performed at 60 ° C. for 3 hours. Then, the polymerization was stopped by cooling. The polymerization rate of vinyl acetate was 55%. The solid content concentration when the polymerization was stopped was 32.5%. Subsequently, unreacted vinyl acetate monomer was removed while sometimes adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 30%) of polyvinyl acetate (PVAc). Furthermore, saponification was performed by adding 5.6 g of an alkaline solution (sodium hydroxide in 10% methanol) to 800 g of PVAc methanol solution prepared by adding methanol thereto (200.0 g of PVAc in the solution). Here, the PVAc concentration of the saponification solution was 25%, and the molar ratio of sodium hydroxide to vinyl acetate units in PVAc was 0.006. A gel-like material was formed in about 15 minutes after the addition of the alkaline solution. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification, and then 500 g of methyl acetate was added to leave the remaining alkali. Neutralized. After confirming that the neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, 2,000 g of methanol was added thereto, and the mixture was allowed to stand and washed at room temperature for 3 hours. After repeating the above washing operation three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain unmodified PVA (PVA1). The resulting PVA1 had a polymerization degree of 1,000 and a saponification degree of 88%.

[Production Example 2] (Production of PVA2)
In Production Example 1, PVA2 was obtained in the same manner as in Production Example 1 except that the amount of vinyl acetate, methanol, initiator and the like and the polymerization rate were changed.

[Production Example 3] (Production of PVA3)
In Production Example 1, PVA3 was obtained in the same manner as Production Example 1 except that the amount of vinyl acetate, methanol, initiator, and the like and the polymerization rate were changed.

[Production Example 4] (Production of PVA4)
In Production Example 1, PVA4 was obtained in the same manner as in Production Example 1 except that the amount of vinyl acetate, methanol, initiator and the like was changed, 6.2 g of stearylmethacrylamide was used, and the polymerization rate was changed.

[Production Example 5] (Production of PVA5)
In Production Example 1, a pressurized reaction vessel was used, the charge amounts of vinyl acetate, methanol, initiator, etc. were changed, ethylene was introduced to maintain the reaction vessel pressure at 0.14 MPa, and the polymerization rate was changed. In the same manner as in Production Example 1, PVA5 was obtained.

[Production Example 6] (Production of PVA6)
In Production Example 1, except for changing the charge amount of vinyl acetate, methanol, initiator, etc., using 11.0 g of itaconic acid, changing the polymerization rate, and changing the alkali molar ratio of sodium hydroxide during saponification, PVA6 was obtained in the same manner as in Production Example 1.

[Production Example 7] (Production of PVA7)
In Production Example 1, the degree of polymerization was 1,700, and the saponification degree was the same as in Production Example 1, except that the amount of vinyl acetate, methanol, initiator, and the like was changed and the alkali molar ratio of sodium hydroxide during saponification was changed. A PVA with a degree of 99 mol% was obtained. 100 parts of the obtained PVA (sodium acetate 0.5%, particle size 7 mesh or less, volatile content 2.5%) was charged into a kneader, and while stirring, 20 parts of acetic acid and 80 parts of acetic anhydride were added to 60 ° C. After heating, the mixture was further stirred at 60 ° C. for 3 hours, 30 parts of diketene was added over 1 hour, and the mixture was further reacted at 60 ° C. for 1 hour to give acetoacetyl having an acetoacetate group content of 2 mol%. PVA was obtained. The obtained acetoacetylated PVA was sufficiently washed with methanol and then dried at 50 ° C. for 18 hours to obtain PVA7.

<Preparation of aqueous emulsion type adhesive>
[Example 1]
PVA1 (polymerization degree 1,000, saponification degree 88%) 87.3 g, ion-exchanged water 1,680 g, Rongalite 0.68 g, sodium acetate in a 5-liter pressure-resistant autoclave equipped with a nitrogen inlet, a thermometer and a stirrer 0.76 g and ferrous chloride 0.03 g were charged and completely dissolved at 95 ° C., and then cooled to 60 ° C. to perform nitrogen substitution. Next, after 1790 g of vinyl acetate was charged, ethylene was pressurized to 45 kg / cm ² and introduced, and 80 g of 4% aqueous hydrogen peroxide solution was injected over 5 hours, and emulsion polymerization was performed at 60 ° C. When the residual vinyl acetate concentration reached 10%, ethylene was released, the ethylene pressure was set to 20 kg / cm ^2, and 4 g of 3% hydrogen peroxide aqueous solution was injected to complete the polymerization. After cooling, the mixture was filtered using a 60 mesh stainless steel wire mesh to obtain an ethylene-vinyl acetate copolymer resin emulsion having a solid content concentration of 55.5% and an ethylene content of 20% by mass. To a mixed solution of 82.3 parts by mass of ion-exchanged water and 2.7 parts by mass of sodium 2-ethylhexyl sulfate as the component (B) with respect to 100 parts by mass of the solid content of the obtained ethylene-vinyl acetate copolymer resin emulsion. Then, 18.5 parts by mass of a 15% solution of PVA3 in which 15 parts by mass of PVA3 was dissolved was added and mixed to prepare an aqueous emulsion adhesive.

[Examples 2 to 8]
The type and amount of the component (A) used, the type and amount of the component (B), and the type, amount, degree of polymerization and degree of saponification of the component (C) used as the polymerization stabilizer or post-treatment agent. Each aqueous emulsion adhesive was prepared in the same manner as in Example 1 except that the changes were made as shown in Tables 1 and 2.

[Example 9]
A 1 L glass polymerization vessel equipped with a reflux condenser, dropping funnel, thermometer, and nitrogen inlet was charged with 300 g of ion-exchanged water and 20.8 g of PVA2 (polymerization degree 1,700, saponification degree 88%) at 95 ° C. Dissolved in. Next, this PVA aqueous solution was cooled, purged with nitrogen, heated to 60 ° C. while stirring at 200 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3 g of 5% aqueous hydrogen peroxide (relative to vinyl acetate, After adding 0.15) in a molar ratio, 23.4 g of vinyl acetate and 2.6 g of Veova 10 (neodecanoic acid vinyl ester: Shell Chemical Co., Ltd.) were charged and polymerization was started. The completion of the initial polymerization (residual amount of vinyl acetate 1% by mass) was confirmed 30 minutes after the start of the polymerization. Next, 0.9 g of a 10% aqueous solution of tartaric acid and 3 g of 5% aqueous hydrogen peroxide were added in a shot, and then 210.6 g of vinyl acetate and 23.4 g of Veova 10 were continuously added over 2 hours to bring the polymerization temperature to 80 ° C. Maintained to complete the polymerization. After cooling, it was filtered using a 60 mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion having a solid content of 47.3% was obtained. PVA3 is mixed with a mixed solution of 53.3 parts by mass of ion-exchanged water and 31.7 parts by mass of sodium 2-ethylhexyl sulfate as a component (B) with respect to 100 parts by mass of the solid content of the obtained polyvinyl acetate emulsion. An aqueous emulsion adhesive was prepared by adding and mixing 15.8 parts by weight of a 15% solution of PVA3 dissolved in 15 parts by weight.

[Example 10]
A 1 L glass polymerization vessel equipped with a reflux condenser, dropping funnel, thermometer, and nitrogen inlet was charged with 300 g of ion-exchanged water and 20.8 g of PVA2 (polymerization degree 1,700, saponification degree 88%) at 95 ° C. Dissolved in. Next, this PVA aqueous solution was cooled, purged with nitrogen, heated to 60 ° C. while stirring at 200 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3 g of 5% aqueous hydrogen peroxide (relative to vinyl acetate, After addition of 0.015) in a molar ratio, 26.0 g of vinyl acetate was charged and polymerization was started. The completion of the initial polymerization (residual amount of vinyl acetate 1% by mass) was confirmed 30 minutes after the start of the polymerization. Next, 0.9 g of a 10% aqueous solution of tartaric acid and 3 g of 5% hydrogen peroxide water were shot, and then 234.0 g of vinyl acetate was continuously added over 2 hours, and the polymerization temperature was maintained at 80 ° C. to complete the polymerization. I let you. After cooling, it was filtered using a 60 mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion having a solid content concentration of 47.4% was obtained. 15 parts by mass of PVA3 in a mixed solution of 21.6 parts by mass of ion exchange water and 63.4 parts by mass of sodium 2-ethylhexyl sulfate as the component (B) with respect to 100 parts by mass of the solid content of the obtained polyvinyl acetate emulsion. An aqueous emulsion adhesive was prepared by adding and mixing 15.8 parts by weight of a partially dissolved 15% solution of PVA3.

[Comparative Examples 1-4]
The type and amount of the component (A) used, the type and amount of the component (B), and the type, amount, degree of polymerization and degree of saponification of the component (C) used as the polymerization stabilizer or post-treatment agent. Each aqueous emulsion adhesive was prepared in the same manner as in Example 1 except that the changes were made as shown in Tables 1 and 2.

<Evaluation>
The following evaluation was performed about each prepared water-based emulsion type adhesive. The results are shown in Table 1.

(Low temperature adhesion)
Adhesive properties were evaluated using a particle board (10 mm thick) and a semi-rigid vinyl chloride sheet. Each aqueous emulsion type adhesive and the test piece were kept for 1 day in a 2 ° C atmosphere and cooled, and each aqueous emulsion type adhesive was placed on a semi-rigid vinyl chloride sheet at a temperature condition of 2 ° C with a bar coater at 90 g / m ^2. (Wet) was applied, bonded to the particle board, degassed with a 2 kg rubber roller, left as it was at 2 ° C. for 1 day, and then forcibly peeled by hand to determine the destruction state. The ratio which the particle board surface destroyed among 10 pieces (tree breakage) is shown. It shows that low temperature adhesiveness is so favorable that the value of a (wood break) ratio is large.

(Measurement of heat resistance (heat-resistant creep))
Each of the aqueous emulsion adhesives prepared above was applied to a plywood (JAS Class 1 etc.) with a roll coater so that the coating amount was 55 g / m ^{2 in} solid content. This was laminated with a polyvinyl chloride film (semi-rigid or rigid) and cured at room temperature for 3 days to obtain a decorative board. The obtained decorative board was placed in an atmosphere of 60 ° C., a static load of 500 g / 25 mm was applied to the polyvinyl chloride film in the 90-degree angle direction, and the heat resistance was evaluated by measuring the length of peeling after 1 hour. . It shows that heat resistance is so favorable that the length of peeling is small.

(Odor)
Four persons directly sniffed each of the aqueous emulsion adhesives prepared above, and judged according to the following criteria.
Unpleasant odor is not felt: ○
Somewhat unpleasant odor: △
There is an unpleasant odor: ×

  As shown in Table 1, it can be seen that the aqueous emulsion adhesives of Examples 1 to 10 are excellent in low-temperature adhesiveness and heat resistance and have low odor. Furthermore, the type and amount of the component (A), the type and amount of the surfactant (B), and the type, amount, degree of polymerization and saponification of the component (C) as a polymerization stabilizer or post-treatment agent used. The adhesives of Examples 2, 3, 7, 8, and 10 that specify the degree are particularly excellent in low-temperature adhesiveness and heat resistance. In addition, it turns out that the low temperature adhesiveness and heat resistance of the water-based emulsion adhesives of Examples 1, 4 to 6 and 9 are slightly decreased. This includes the type and amount of the component (A), the type and amount of the surfactant (B), and the type and presence / absence, amount of the component (C) as the polymerization stabilizer or post-treatment agent used, This is considered to be caused by the degree of polymerization.

  On the other hand, when the surfactant (B) does not satisfy the prescribed requirements (Comparative Examples 1 to 4), it can be seen that the low-temperature adhesiveness and heat resistance are reduced, and odor is generated.

  The aqueous emulsion adhesive of the present invention is excellent in low-temperature adhesiveness and heat resistance and has a low odor. Therefore, the aqueous emulsion adhesive of the present invention is not limited to adhesives for wood and plastic, paper and plastic, inorganic material and plastic, metal and paper, etc., but is also suitable for woodworking, paper packaging, general use, etc. Used for.

Claims (1)

Using polyvinyl alcohol (C) as a polymerization stabilizer to obtain an aqueous emulsion containing a vinyl acetate (co) polymer (A) by (co) polymerization of a monomer containing vinyl acetate in an aqueous medium;
In the aqueous emulsion, a branched alkoxy group having 7 to 29 carbon atoms (R ¹ And a group selected from a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a sulfuric acid group or a salt thereof, and a polyoxyalkylene group (X ¹ And (b) adding a surfactant (B) having
A step of adding polyvinyl alcohol (C) to the aqueous emulsion.
A method for producing an aqueous emulsion adhesive having