Manufacturing method for polyvinyl acetate-based water-based emulsion adhesive

Abstract

To provide a production method of a polyvinyl acetate-based aqueous emulsion adhesive having a fine average particle size.SOLUTION: A dispersion liquid containing the following nonionic surface active agent, polyvinyl alcohol, and anionic surface active agent is prepared. The nonionic surface active agent is a tri-block copolymer having a mass average molecular weight of 4,200 constituted by arranging polyoxyethylene, polyoxypropylene, and polyoxyethylene in this order, where polyoxyethylene:polyoxypropylene=40:60 (pts.mass), and the cloud point is 60°C. The polyvinyl alcohol has a polymerization degree of 300, and a saponification degree of 88 mol%. The anionic surface active agent is sodium dodecylbenzenesulfonate. A polyvinyl acetate-based aqueous emulsion adhesive is obtained by stirring while dropping a vinyl acetate monomer and a polymerization initiator in the dispersion liquid to subject the same to emulsion polymerization.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polyvinyl acetate aqueous emulsion adhesive used for paper such as corrugated cardboard, and more particularly to a method for producing a polyvinyl acetate aqueous emulsion adhesive suitable for nozzle application. [Background technology]

[0002] Conventionally, polyvinyl acetate aqueous emulsion adhesives for paper have been obtained by emulsion polymerization of vinyl acetate monomers using polyvinyl alcohol as a protective colloid. Patent Document 1 describes adjusting the average particle size of emulsion particles to 0.5 to 1.5 μm in order to improve the initial adhesive strength of this adhesive.

[0003] However, when the average particle diameter is about 0.5 to 1.5 μm, nozzle clogging is likely to occur during nozzle application, and the adhesive is difficult to eject uniformly. In this specification, when such problems occur during nozzle application, this is referred to as poor nozzle suitability. In this specification, when such problems are unlikely to occur, this is referred to as excellent nozzle suitability.

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-294194 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing a polyvinyl acetate-based aqueous emulsion adhesive having a finer average particle size of emulsion particles and excellent nozzle suitability. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors of the present invention have conducted various studies and found that emulsion polymerization in the presence of a specific nonionic surfactant can produce a polyvinyl acetate aqueous emulsion adhesive with a small average particle size of emulsion particles, thereby arriving at the present invention. That is, the present invention relates to a method for preparing a vinyl acetate monomer solution by subjecting a vinyl acetate monomer solution to a polymerization reaction with a nonionic surfactant and a triblock copolymer consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene units arranged in this order, the triblock copolymer having a cloud point in the range of 60°C to 80°C. 5 parts by mass or less (excluding 0 part by mass) of polyvinyl alcohol per 115 parts by mass of the vinyl acetate monomer and / or 0.6 to 1.5 parts by mass of an anionic surfactant per 1 part by mass of the nonionic surfactant The present invention relates to a method for producing a polyvinyl acetate aqueous emulsion adhesive, characterized by emulsion polymerization in a dispersion containing: (a) a polyvinyl acetate aqueous emulsion adhesive having a small average particle size; and (b) a polyvinyl acetate aqueous emulsion adhesive having a volume-based median size of emulsion particles of 200 nm or less.

[0007] The monomer liquid used in the present invention is mainly composed of vinyl acetate monomer. The monomer liquid may contain a monomer copolymerizable with vinyl acetate monomer, such as an acrylic acid monomer or an acrylate monomer.

[0008] Vinyl acetate monomer is emulsion polymerized in a dispersion containing a specific nonionic surfactant. The specific nonionic surfactant is a triblock copolymer consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene units and having a cloud point in the range of 60°C to 80°C. Nonionic surfactants that are not triblock copolymers are not preferred because they do not produce stable emulsion adhesives or emulsion adhesives with a small average particle size. Furthermore, triblock copolymers with a cloud point below 60°C or above 80°C are not preferred because they do not produce stable emulsion adhesives or emulsion adhesives with a small average particle size.

[0009] The mass average molecular weight of the triblock copolymer is preferably approximately 2000 to 5000. If the mass average molecular weight is outside this range, the cloud point tends to be difficult to achieve within the range of 60°C to 80°C. The mass ratio of polyoxyethylene to polyoxypropylene is approximately polyoxyethylene:polyoxypropylene = 30-50:70-50 (total 100 parts by mass). If the mass average molecular weight is outside this range, the cloud point tends to be difficult to achieve within the range of 60°C to 80°C.

[0010] The specific nonionic surfactant is preferably present in an amount of 2 to 4 parts by weight per 115 parts by weight of vinyl acetate monomer. If the amount is less than 2 parts by weight or more than 4 parts by weight, a stable emulsion adhesive may not be obtained, or it may be difficult to obtain an emulsion adhesive with a fine average particle size.

[0011] Polyvinyl alcohol and / or anionic surfactants are added and mixed together with a specific nonionic surfactant. Polyvinyl alcohols that have traditionally been used as protective colloids can be used. In the present invention, it is particularly preferable to use polyvinyl alcohols with a degree of polymerization of 1000 or less and a degree of saponification of 90 mol% or less. Conventional anionic surfactants can be used, such as sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate.

[0012] The mass of polyvinyl alcohol to be added and mixed is not a problem as long as it is the mass conventionally used as a protective colloid. In particular, since the present invention uses it in combination with a specific nonionic surfactant, a smaller amount than conventionally is acceptable. Specifically, it is 5 parts by mass or less per 115 parts by mass of vinyl acetate monomer. (However, 0 parts by mass is excluded.) Since it is assumed that polyvinyl alcohol is added and mixed, 0 parts by mass is excluded, as shown in parentheses.

[0013] The mass of the anionic surfactant to be added and mixed is 0.6 to 1.5 parts by mass per 1 part by mass of the specific nonionic surfactant. If the amount of the anionic surfactant added and mixed is less than 0.6 parts by mass or more than 1.5 parts by mass, the balance will be poor and a stable emulsion adhesive may not be obtained.

[0014] The manufacturing method of the present invention is similar to the known procedure for manufacturing conventional polyvinyl acetate-based aqueous emulsion adhesives. That is, first, a dispersion in which a specific nonionic surfactant is dissolved or dispersed is prepared. In this dispersion, A predetermined amount Polyvinyl alcohol and / or anionic surfactant are dissolved or dispersed. Ku Then, a monomer liquid containing vinyl acetate monomer and a polymerization initiator are added to this dispersion and emulsion polymerization is carried out to obtain a polyvinyl acetate aqueous emulsion adhesive. The median diameter of the emulsion particles in the obtained polyvinyl acetate aqueous emulsion adhesive is approximately 100 to 200 nm on a volume basis. [Effects of the Invention]

[0015] The method according to the present invention has the effect of producing a polyvinyl acetate-based aqueous emulsion adhesive having emulsion particles with a small average particle size and excellent nozzle suitability. [Example]

[0016] Example 1 The following raw materials were prepared: Nonionic surfactant (1): "Pluronic P-84" manufactured by ADEKA Corporation (a triblock copolymer having a mass average molecular weight of 4200 and consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene in that order, with a polyoxyethylene:polyoxypropylene ratio of 40:60 (parts by mass), and a cloud point of 60°C.) Polyvinyl alcohol (1): "JP-03" manufactured by Nippon Vinyl Acetate & Poval Co., Ltd. (Polyvinyl alcohol with a degree of polymerization of 300 and a degree of saponification of 88 mol%). Polymerization initiator: A uniform mixture of 0.25 parts by mass of ammonium peroxodisulfate, 0.2 parts by mass of sodium bicarbonate, and 3 parts by mass of ion-exchanged water (total 3.45 parts by mass). Antifoaming agent: Sannobuco's "Noptam 8034F" (a mixture of mineral oil, silica, and polyoxyalkylene-type nonionic surfactants, etc.)

[0017] A glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a polymerization initiator dropping inlet was charged with 100 parts by mass of ion-exchanged water and 0.05 parts by mass of antifoaming agent, followed by the addition of 3.75 parts by mass of nonionic surfactant (1) and 2.5 parts by mass of polyvinyl alcohol (1), and the mixture was stirred while heating to approximately 90°C to obtain a uniform dispersion. This dispersion was then heated to 85°C, and 115 parts by mass of vinyl acetate monomer liquid and 3.45 parts by mass of polymerization initiator were added dropwise while stirring for 2 hours to carry out emulsion polymerization, yielding a polyvinyl acetate-based aqueous emulsion adhesive.

[0018] Example 2 Emulsion polymerization was carried out in the same manner as in Example 1, except that the amount of nonionic surfactant (1) used was changed to 2.5 parts by mass, to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0019] Example 3 The following raw materials were prepared: Anionic surfactant: Kao Corporation's "Neopelex G-65" (sodium dodecylbenzenesulfonate) Emulsion polymerization was carried out in the same manner as in Example 1, except that 2.5 parts by mass of an anionic surfactant was used instead of 2.5 parts by mass of polyvinyl alcohol (1), to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0020] Example 4 A polyvinyl acetate-based aqueous emulsion adhesive was obtained by carrying out emulsion polymerization in the same manner as in Example 2, except that 3.75 parts by mass of an anionic surfactant was used instead of 2.5 parts by mass of polyvinyl alcohol (1).

[0021] Example 5 Emulsion polymerization was carried out in the same manner as in Example 3, except that 1.25 parts by mass of polyvinyl alcohol (1) was further added, to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0022] Example 6 The following raw materials were prepared: Nonionic surfactant (2): "Pluronic P-85" manufactured by ADEKA Corporation (a triblock copolymer having a mass average molecular weight of 4600 and consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene in that order, with a polyoxyethylene:polyoxypropylene ratio of 50:50 (parts by mass), and a cloud point of 75°C.) Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (2) was used instead of nonionic surfactant (1), to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0023] Example 7 The following raw materials were prepared: Nonionic surfactant (3): "Pluronic P-103" manufactured by ADEKA Corporation (a triblock copolymer having a mass average molecular weight of 4900 and an arrangement of polyoxyethylene-polyoxypropylene-polyoxyethylene in that order, with a polyoxyethylene:polyoxypropylene ratio of 30:70 (parts by mass), and a cloud point of 67°C.) Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (3) was used instead of nonionic surfactant (1), to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0024] Example 8 The following raw materials were prepared: Polyvinyl alcohol (2): "JP-10" manufactured by Nippon Vinyl Acetate & Poval Co., Ltd. (Polyvinyl alcohol with a polymerization degree of 1000 and a saponification degree of 88 mol%). Emulsion polymerization was carried out in the same manner as in Example 5, except that 1.25 parts by mass of polyvinyl alcohol (2) was used instead of 1.25 parts by mass of polyvinyl alcohol (1), to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0025] Comparative Example 1 The following raw materials were prepared: Nonionic surfactant (4): "Pluronic L-81" manufactured by ADEKA Corporation (a triblock copolymer having a mass average molecular weight of 2000 and consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene in that order, with a polyoxyethylene:polyoxypropylene ratio of 10:90 (parts by mass), and a cloud point of 24°C.) Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (4) was used instead of nonionic surfactant (1).

[0026] Comparative Example 2 The following raw materials were prepared: Nonionic surfactant (5): "Pluronic F-88" manufactured by ADEKA Corporation (a triblock copolymer having a mass average molecular weight of 2000 and consisting of polyoxyethylene-polyoxypropylene-polyoxyethylene in that order, with a polyoxyethylene:polyoxypropylene ratio of 80:20 (parts by mass), and a cloud point of 100°C or higher). Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (5) was used instead of nonionic surfactant (1).

[0027] Comparative Example 3 The following raw materials were prepared: Nonionic surfactant (6): Kao Corporation's "Emulgen A-60" (a nonionic surfactant made of polyoxyethylene distyrenated phenyl ether with a cloud point of 62°C). Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (6) was used instead of nonionic surfactant (1).

[0028] Comparative Example 4 The following raw materials were prepared: Nonionic surfactant (7): "DKS NL-70" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (a nonionic surfactant made of polyoxyethylene lauryl ether with a cloud point of 62°C.) Emulsion polymerization was carried out in the same manner as in Example 5, except that nonionic surfactant (7) was used instead of nonionic surfactant (1), to obtain a polyvinyl acetate-based aqueous emulsion adhesive.

[0029] Comparative Example 5 The following raw materials were prepared: Nonionic surfactant (8): "Brownon EL-1509" manufactured by Aoki Oil & Fat Industries Co., Ltd. (a nonionic surfactant made of polyoxyethylene oleyl ether with a cloud point of 61°C.) Emulsion polymerization was carried out in the same manner as in Example 5, except that the nonionic surfactant (1) was replaced with the nonionic surfactant (8).

[0030] Comparative Example 6 Emulsion polymerization was carried out in the same manner as in Example 3, except that the nonionic surfactant (1) was not used and the amount of the anionic surfactant was increased to 6.25 parts by mass.

[0031] According to the methods of Examples 1 to 8 and Comparative Example 4, emulsion polymerization was stably carried out and polyvinyl acetate-based aqueous emulsion adhesives were obtained. On the other hand, according to the methods of Comparative Examples 1 to 3, 5, and 6, emulsion polymerization could not be stably carried out and a uniform and stable polyvinyl acetate-based aqueous emulsion adhesive could not be obtained.

[0032] The average particle size (median size on a volume basis) of the emulsion particles of the polyvinyl acetate-based aqueous emulsion adhesives obtained by the methods of Examples 1 to 8 and Comparative Example 4 was measured using a Nanotrac Wave EX150 particle size distribution meter (a particle size measuring device using laser diffraction and scattering) manufactured by Nikkiso Co., Ltd. The results are shown in Table 1.

[0033] [Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━ Median diameter of emulsion particles ━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 180 nm Example 2 170 nm Example 3 160 nm Example 4 160 nm Example 5 160 nm Example 6 140 nm Example 7 160 nm Example 8 160 nm Comparative example 4 230nm ━━━━━━━━━━━━━━━━━━━━━━━━━━

[0034] As can be seen from Table 1, the emulsion particles of the polyvinyl acetate-based aqueous emulsion adhesives obtained by the methods of Examples 1 to 8 have a small average particle size and are excellent in nozzle suitability.

Claims

1. A method for producing a polyvinyl acetate-based aqueous emulsion adhesive, characterized by emulsion-polymerizing a monomer liquid containing vinyl acetate monomer in a dispersion containing a nonionic surfactant that is a triblock copolymer in which polyoxyethylene-polyoxypropylene-polyoxyethylene are arranged in this order and has a cloud point within the range of 60°C to 80°C, and 5 parts by mass or less (excluding 0 part by mass) of polyvinyl alcohol per 115 parts by mass of the vinyl acetate monomer and / or 0.6 to 1.5 parts by mass of an anionic surfactant per 1 part by mass of the nonionic surfactant.

2. 2. The method for producing a polyvinyl acetate aqueous emulsion adhesive according to claim 1, wherein the polyvinyl alcohol has a degree of polymerization of 1,000 or less and a degree of saponification of 90 mol % or less.

3. 2. The method for producing a polyvinyl acetate aqueous emulsion adhesive according to claim 1, wherein the anionic surfactant is sodium dodecylbenzenesulfonate.

4. 2. The method for producing a polyvinyl acetate aqueous emulsion adhesive according to claim 1, wherein 2 to 4 parts by weight of a nonionic surfactant is used per 115 parts by weight of vinyl acetate monomer.