JP4330127B2 - Adhesive composition and synthesis method thereof - Google Patents

Description

  The present invention is a novel adhesive composition, specifically, a resin emulsion that is excellent in polymerization stability, low-temperature workability, and storage stability even when it has a high solid content, and does not contain a plasticizer that raises concerns about environmental hormones. It is related with the adhesive composition which consists of, and its synthesis | combining method.

  Vinyl acetate resin emulsions obtained by emulsion polymerization of vinyl acetate monomers and below (described as VAc) have been widely used in adhesives, paints, paper processing, fiber processing, and the like. The demand for higher performance and higher functionality is increasing year by year.

  As a measure for higher performance and higher functionality to meet these requirements, a method using polyvinyl alcohol modified with a functional group (hereinafter abbreviated as PVA), a method using a special polymer as a protective colloid, and a functional group A method of copolymerizing a monomer with a vinyl acetate monomer (hereinafter abbreviated as VAc) has been proposed.

  However, when modified PVA is used or when a functional monomer is copolymerized, there is a tendency that the polymerization stability, storage stability, etc. tend to decrease.

  For example, Patent Document 1 proposes a method of improving water resistance by copolymerizing VAc and an acetoacetyl group-containing monomer using acetoacetylated PVA as a protective colloid, but crosslinking proceeds during storage. As a result, the storage stability is poor and the usable period is limited.

  On the other hand, attempts have been made to improve the storage stability, low-temperature workability, etc. while improving the performance and functionality as described above by setting the particle size of the resin emulsion within a specific range, but it has not been completed yet. I have not seen.

In the case of water-based adhesives, such as vinyl acetate resin emulsions, studies on high solidification have been conducted to improve drying properties, but on the other hand, since the polymerization stability and storage stability are reduced, the solid content is reduced. At present, it is difficult to set it to 50% or more and it has not been put into practical use.
Japanese Patent No. 2928369 JP-A-11-92734 JP 2000-239307 A

  In the present invention, in order to solve the above-described problems, a resin emulsion for seeds having different average particle diameters is used in combination, and by controlling the particle diameter of the resin emulsion to a specific range, In any case, an adhesive composition that is excellent in polymerization stability, low-temperature workability, storage stability and the like is to be developed.

The invention of claim 1, which has been made to solve the above problems, includes at least two seed resin emulsions having an average particle diameter of 50 to 500 nm and a seed resin emulsion having an average particle diameter of 500 to 1500 nm. in the presence of more seeds resin emulsion, polyvinyl alcohol as a protective colloid, Ri vinyl acetate monomer emulsion polymerized resin emulsion Tona prepared by solid content of the seed for the resin emulsion is a resin emulsion total solids 5 It is -25 weight%, It is an adhesive composition characterized by the above-mentioned.

A second aspect of the present invention is the adhesive composition according to the first aspect, wherein 50 to 500 μm volume% of the synthesized resin emulsion is 15 to 85 .

According to a third aspect of the invention, in the presence of two or more different seed resin emulsions including a seed resin emulsion having an average particle diameter of 50 to 500 nm and a seed resin emulsion having an average particle diameter of 500 to 1500 nm. A method for synthesizing an adhesive composition comprising emulsion-polymerizing a vinyl acetate monomer using polyvinyl alcohol as a protective colloid and the solid content of the resin emulsion for seeds in the range of 5 to 25% by weight of the total solid content of the resin emulsion It is.

  The adhesive composition according to the present invention comprises a resin emulsion prepared by emulsion polymerization of VAc in the presence of a resin emulsion for seeds having different average particle sizes. The emulsion polymerized resin emulsion has a large particle size. Since those having a small particle size are mixed, even a high solid content is prepared with excellent low-temperature workability and storage stability.

  In particular, when the average particle diameter of one seed resin emulsion is 50 to 500 nm and the average particle diameter of another seed resin emulsion is 500 to 1500 nm, such characteristics are remarkably obtained. There is no worry about all-season use. Moreover, since it does not contain a plasticizer that is suspected of being an environmental hormone, it can be used safely in various fields.

  Hereinafter, the adhesive composition according to the present invention will be described.

  The adhesive composition of the present invention is prepared by emulsion polymerization of VAc in the presence of a polymerization initiator in an aqueous emulsion containing PVA as a protective colloid in the presence of two or more different seed resin emulsions.

  Resin emulsion for seed includes acrylic resin emulsion, ethylene / vinyl acetate resin emulsion, vinyl acetate resin emulsion, styrene / butadiene copolymer emulsion, acrylonitrile butadiene copolymer emulsion, chloroprene rubber latex, urethane resin emulsion, epoxy resin emulsion, etc. Of these, at least one of them is preferably selected from a VAc polymerizable acrylic resin emulsion, an ethylene / vinyl acetate resin emulsion, a vinyl acetate resin emulsion, and a urethane resin emulsion.

  As the particle diameter of the resin emulsion for seeds of the present invention, it is preferable that at least one average particle diameter is 50 to 500 nm. VAC emulsion polymerization using PVA as a protective colloid makes it difficult to obtain particles of 500 nm or less, so by using a seed resin emulsion with an average particle size of 50 to 500 nm, particles of 500 nm or less are generated and the filling degree is increased. It can be finished to a high solid content.

  More preferably, one seed resin emulsion has an average particle size of 50 to 500 nm, and the other seed resin emulsion has an average particle size of 500 to 1500 nm. If combined in this way, particles of 500 nm or less and particles of 500 nm or more can be obtained reliably.

  In addition, when the particle size is 50 nm or less, the particle size of the generated particles is small and unstable, so that it is not suitable for high solid differentiation. A resin emulsion having a particle size of 1500 nm or more is not suitable for use because the resulting resin emulsion particles become large and cause problems such as sedimentation during storage.

  Moreover, in order to perform high solid differentiation while ensuring polymerization stability and storage stability, 50 to 500 nm volume% is preferably 15 to 85%.

  If it is 15% or less, it is not suitable because a decrease in polymerization stability and deterioration in storage stability are observed, and if it is 85% or more, it is not preferable because a decrease in polymerization stability and deterioration in storage stability are also observed.

  Further, the use amount of the resin emulsion for seed is suitably 5 to 25% by weight based on the total solid content of the resin emulsion to be synthesized.

  The effect of controlling the particle size is difficult to obtain because it is too small at 5% by weight or less. If it is 25% by weight or more, polymerization stability cannot be obtained, which is not preferable.

  By using a seed resin emulsion having a different average particle size in combination, the emulsion-polymerized resin emulsion is prepared to have a mixture of a large particle size and a small particle size. Therefore, a resin emulsion having a filling property and capable of emulsion polymerization even at a high solid content and having stability can be obtained.

  PVA is suitable for the protective colloid because it has good polymerization stability. Especially, those having a saponification degree of 87 to 99% and a polymerization degree of 400 to 4000 are polymerization stability, storage stability, low-temperature film-forming property, A single or a plurality of PVA are used in combination because of excellent balance of structural viscosity, water resistance and the like.

  A water-soluble polymer such as hydroxyethyl cellulose, gum arabic, or carboxycellulose may be used in combination so as not to impair the original performance.

  Acrylic resin emulsion for seed includes acrylic esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate. Commercially available products obtained by emulsion (co) polymerization of acrylic monomers such as styrene, vinyltoluene, and acrylamide with a known method in the presence of protective colloids are used.

  The average particle size of these acrylic resin emulsions is suitably 50 to 500 nm in order to prepare a resin emulsion having a small particle size as described above.

  On the other hand, it is also possible to prepare an acrylic resin emulsion of 500 nm or more by a technique using PVA as a protective colloid. For example, an acrylic resin emulsion having an average particle diameter of 50 to 500 nm and an acrylic resin emulsion having an average particle diameter of 500 to 1500 nm It is also possible to use in combination.

  Ethylene / vinyl acetate resin emulsions for seeds can be synthesized by a known synthesis method, and those having an average particle size of 50 to 500 nm and 500 to 1500 nm as appropriate are used as described above. .

  As the seed vinyl acetate resin emulsion, one synthesized by a known method is used, and those having an average particle diameter of 50 to 500 nm and an average particle diameter of 500 to 1500 nm can be appropriately selected and used as described above. .

  Further, a resin emulsion in which various monomers copolymerizable with VAc are copolymerized may be used.

  For urethane resin emulsion for seed, polyester polyol or polyether polyol, low molecular weight diol or diamine, and diisocyanate are reacted to synthesize high molecular weight linear polyurethane, which is then organic solvent such as toluene, acetone, tetrahydrofuran, etc. Phase inversion emulsification method in which an aqueous emulsifier solution is dropped and stirred to force emulsification, a prepolymer having a terminal isocyanate group is emulsified in water by mechanical stirring using an emulsifier, the main chain of the urethane resin or What was prepared by the method etc. which introduce | transduce a sulfonate, carboxylate, etc. into a side chain and make it a self-emulsification type is used.

  The average particle size can be appropriately selected and used as described above.

  In addition, styrene butadiene rubber latex, chloroprene rubber latex, and acrylonitrile butadiene rubber latex used for seeds are prepared by a known method. These average particle diameters can be appropriately selected and used as described above.

  As the polymerization initiator, a peroxide-based initiator, an azo-based initiator, a persulfate-based initiator, or the like is used.

  Examples of peroxide initiators include benzoyl peroxide, lauryl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, butyl hydroperoxide, and hydrogen peroxide.

  Examples of the azo initiator include azobisisobutylnitrile, azobiscyanovaleric acid, azobiscyanopentanoic acid, and the like.

  Examples of the persulfate-based initiator include ammonium persulfate, potassium persulfate, and sodium persulfate.

  In addition, as a polymerization regulator, for example, thioglycolic acid, butine mercaptan, dodecyl mercaptan, octyl mercaptan, lauryl mercaptan, and the like may be used as appropriate.

  The seed polymerization can be carried out while adding VAc using a polymerization initiator in the presence of a resin emulsion having a different average particle size by mixing and dissolving water and PVA as a protective colloid in a polymerization reaction vessel. In this case, a part or all of VAc is added to the polymerization vessel together with the polymerization initiator, water and the resin emulsion for seed, or part or all of VAc is added continuously or intermittently during the polymerization. Can proceed.

  In addition to VAc, it can also be copolymerized with a comonomer such as (meth) acrylic acid ester, vinyl propionate, vinyl versatate, (meth) acrylic acid and the like. If necessary, fillers, pigments, antifoaming agents, preservatives and the like can be added as needed.

  The polymerization temperature varies depending on the type of polymerization initiator used. For example, when polymerization is advanced by thermal decomposition such as ammonium persulfate, a temperature of 60 ° C. or higher is suitable. Moreover, in the redox type | system | group which combined the peroxide and the reducing agent, it can advance at 60 degrees C or less.

  Hereinafter, examples and comparative examples will be described. In addition, a weight part is described as a part.

Examples 1-5 Water 1, PVA (saponification degree 88%, average polymerization degree 500) in a reaction vessel, seed resin emulsion, butyl acrylate / styrene copolymer resin emulsion (hereinafter referred to as acrylic 1, resin solid content) 55%, pH 8, average particle size 200 nm), 2-ethylhexyl acrylate / methyl methacrylate copolymer resin emulsion (hereinafter referred to as acrylic 2, resin content 55%, pH 9, average particle size 600 nm), ethylene / vinyl acetate resin emulsion (Hereinafter referred to as EVA1, resin solid content 55%, pH 6, average particle diameter 1100 nm), urethane resin emulsion (hereinafter referred to as U1, resin solid content 45%, pH 8, average particle diameter 220 nm) and vinyl acetate resin emulsion (hereinafter PVAc1) , Resin solid content 40%, pH 4, average particle diameter 1400 m) is charged, heated and kept at 80 ° C. while stirring, vinyl acetate (Vac), acrylic acid and ammonium persulfate dissolved in water 2 are added dropwise over 3 hours to proceed with emulsion polymerization. Then, after stirring for 60 minutes at the same temperature and cooling, Example 1 [Solid content of resin emulsion for seed (hereinafter referred to as seed solid content ratio) is 24.7% with respect to total solid content of resin emulsion], Example 2 (seed solid fraction 7.8%), Example 3 (seed solid fraction 15.3%), Example 4 (seed solid fraction 21.7%), Example 5 (seed solid fraction 13. 6%) resin emulsion was obtained. The seed solid content ratio can calculate the solid amount of the seed resin emulsion from the blended amount and solid content of the seed resin emulsion, and can calculate the total solid amount of the resin emulsion from the total amount of the resin emulsion and the non-volatile content (solid content). It can be calculated from both solids. For example, in the case of Example 1, the solid amount of the seed resin emulsion is 75 × 0.55 + 110 × 0.55 = 101.75, and the total solid amount of the resin emulsion is 725.5 × 0.568 = 412.084. 101.75 / 412.084≈0.247, the seed solid content ratio is 24.7%.

  Table 1 shows the measurement results of the properties, polymerization stability, low-temperature workability, and storage stability of the resin emulsion of each example.

Comparative Examples 1-5 Comparative Example 1 (seed solid content ratio 0%), Comparative Example 2 (seed solid content ratio 2.7%), and Comparative Example 3 (seed solid content) in the same manner as in the examples according to the formulation in Table 2 Resin emulsions of 30.5%), Comparative Example 4 (seed solid content 16.0%), and Comparative Example 5 (seed solid content 16.7%) were prepared.
Table 2 shows the measurement results of the properties, polymerization stability, low temperature workability, and storage stability of the obtained resin emulsions of each Comparative Example.

Measurement / Evaluation Method Average particle diameter: Measurement (volume reference value) using a laser type particle diameter measuring instrument manufactured by Malvern Instruments Ltd.
2.50 to 500 μm volume%: Calculated by summing the volume% of the 50 to 500 μm portion from the measured value of the average particle diameter.
3. Polymerization stability: The product is filtered through a mesh of 100 mesh, the residue is dried, and the polymerization stability is evaluated by the weight (g).
4). Low-temperature workability: The magnification of the viscosity at 23 ° C. and the viscosity at 0 ° C. measured by a BH viscometer is measured, and a low magnification is evaluated as having good low-temperature workability.
5. Storage stability: The viscosity at 40 ° C. is measured, the viscosity after 28 days storage at 40 ° C. is measured, and the one with a low magnification is evaluated as having good storage stability.

  The adhesive composition according to the present invention contains a resin emulsion having a large particle size and a small particle size, and thus is prepared to have excellent low-temperature workability and storage stability even at a high solid content. Since it does not contain a plasticizer that is a concern, it can be used safely in all seasons for paper processing, wood processing, and other various adhesive applications.

Claims (3)

Polyvinyl alcohol is used as a protective colloid in the presence of at least two different seed resin emulsions including a seed resin emulsion having an average particle diameter of 50 to 500 nm and a seed resin emulsion having an average particle diameter of 500 to 1500 nm. , resin emulsion Tona prepared by emulsion polymerization of vinyl acetate monomer is, the adhesive composition have a solid content of the seed resin emulsion is characterized in that 5 to 25% by weight of the resin emulsion total solids. The adhesive composition according to claim 1, wherein 50 to 500 nm volume% of the synthesized resin emulsion is 15 to 85. Polyvinyl alcohol is used as a protective colloid in the presence of at least two different seed resin emulsions including a seed resin emulsion having an average particle diameter of 50 to 500 nm and a seed resin emulsion having an average particle diameter of 500 to 1500 nm. A method for synthesizing an adhesive composition comprising emulsion-polymerizing a vinyl acetate monomer with a solid content of the resin emulsion for seeds in the range of 5 to 25% by weight of the total solid content of the resin emulsion .