JP5427309B1 - Adhesive and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently producing a highly water-resistant adhesive containing a vinyl acetate resin emulsion and an inorganic powder while suppressing this occurrence.
SOLUTION: A method for producing an adhesive comprising a vinyl acetate resin emulsion and an inorganic powder, emulsion polymerization of a vinyl acetate monomer using polyvinyl alcohol containing acetoacetylated polyvinyl alcohol as a protective colloid, or vinyl acetate monomer. And a copolymerization step of emulsion-copolymerizing a monomer having an acetoacetyl group to obtain the vinyl acetate resin emulsion, and preparing a paste by dispersing at least a part of the inorganic powder in an aqueous solution in which polyvinyl alcohol is dissolved A dispersion step and a mixing step of mixing and stirring the prepared paste in the obtained vinyl acetate resin emulsion are configured.
[Selection figure] None

Description

  The present invention relates to an adhesive excellent in adhesiveness and water resistance, and a method for producing the same.

  Acetoacetylated vinyl acetate resin emulsions are widely used as highly water-resistant adhesives for paper products, wood, fibers and the like because of their high water resistance. The vinyl acetate resin emulsion can be produced by emulsion polymerization of a vinyl acetate monomer in the presence of acetoacetylated polyvinyl alcohol, or emulsion copolymerization of a vinyl acetate monomer and a monomer having an acetoacetyl group. . A pigment, an extender, a plasticizer, a stabilizer and the like are appropriately blended in the obtained vinyl acetate resin emulsion as necessary to produce an adhesive.

JP-A 61-197649 JP 2000-282004 A JP 2010-229307 A JP 2005-31496 A

  As the pigment and extender, powdered materials such as calcium carbonate, clay and titanium oxide are often used. For example, if a powder such as calcium carbonate is blended in a vinyl acetate resin emulsion as it is, the dispersibility of the powder is poor, and it is easy to produce lumps. Once in this state, it is difficult to disintegrate and disperse it by stirring. Before shipping as a product, filtration is performed to remove foreign matter. However, if mushrooms are generated, it takes a long time for the filtering work.

  The present invention has been made in view of such a situation, and an adhesive containing a vinyl acetate resin emulsion and an inorganic powder can be efficiently produced at a low cost while suppressing this occurrence. It is an issue to provide. Another object of the present invention is to provide an adhesive having excellent adhesiveness and water resistance by adopting the production method.

  (1) In order to solve the above-mentioned problems, the method for producing an adhesive of the present invention is a method for producing an adhesive comprising a vinyl acetate resin emulsion and an inorganic powder, and includes polyvinyl containing acetoacetylated polyvinyl alcohol. Polymerization step of emulsion polymerization of vinyl acetate monomer or emulsion copolymerization of vinyl acetate monomer and monomer having acetoacetyl group using alcohol as protective colloid to obtain the vinyl acetate resin emulsion, and dissolving polyvinyl alcohol A pre-dispersing step of preparing a paste by dispersing at least a part of the inorganic powder in an aqueous solution, and a mixing step of mixing and stirring the prepared paste in the obtained vinyl acetate resin emulsion It is characterized by.

  In the production method of the present invention, at least a part of the inorganic powder is dispersed in an aqueous solution in which polyvinyl alcohol is dissolved in advance (hereinafter referred to as “PVA aqueous solution” as appropriate) (preliminary dispersion step). Before blending into the vinyl acetate resin emulsion, the inorganic powder is dispersed in the PVA aqueous solution, whereby this occurrence can be suppressed as it is when blended into the vinyl acetate resin emulsion. Thereby, stirring work and filtration work can be performed smoothly.

  The polyvinyl alcohol used as the dispersion medium for the inorganic powder may be the same as or different from the polyvinyl alcohol used as the protective colloid. Moreover, the viscosity of a dispersion medium can be made high by using polyvinyl alcohol as a dispersion medium. Thereby, since an appropriate share is applied to the inorganic powder during preliminary dispersion, the inorganic powder is easily dispersed. Moreover, since polyvinyl alcohol which is one component of the adhesive is used as the dispersion medium, it is difficult to hinder the adhesive performance. As described above, according to the production method of the present invention, it is possible to produce the adhesive efficiently and at low cost while suppressing the occurrence while maintaining the adhesiveness of the vinyl acetate resin emulsion.

  (2) The adhesive of the present invention includes a vinyl acetate resin emulsion using polyvinyl alcohol containing acetoacetylated polyvinyl alcohol as a protective colloid, and an inorganic powder, and is manufactured by the manufacturing method having the configuration of (1) above. It is characterized by that.

  The adhesive of the present invention is produced by adding a paste in which an inorganic powder is dispersed in a PVA aqueous solution to a vinyl acetate resin emulsion. Since this generation is suppressed as it is in the manufacturing process, it is excellent in workability and has high adhesiveness and water resistance.

  According to the manufacturing method of the present invention, while maintaining the adhesiveness of the vinyl acetate resin emulsion, the dispersibility of the inorganic powder to be blended is improved, and an adhesive having excellent adhesiveness and water resistance is manufactured efficiently and at low cost. can do.

  Hereinafter, embodiments of the adhesive and the method for producing the same according to the present invention will be described. The adhesive of the present invention and the method for producing the same are not limited to the following forms, and can be variously modified and improved by those skilled in the art without departing from the gist of the present invention. Can be implemented.

<Method for producing adhesive>
The method for producing an adhesive of the present invention is a method for producing an adhesive comprising a vinyl acetate resin emulsion and an inorganic powder, and includes a polymerization step, a preliminary dispersion step, and a mixing step. Below, each process is demonstrated in order.

(1) Polymerization step In this step, polyvinyl acetate containing acetoacetylated polyvinyl alcohol is used as a protective colloid, and vinyl acetate monomer is emulsion-polymerized, or vinyl acetate monomer and monomer having an acetoacetyl group are emulsion-copolymerized, This is a step of obtaining the vinyl acetate resin emulsion.

  As the protective colloid, polyvinyl alcohol containing acetoacetylated polyvinyl alcohol (hereinafter appropriately referred to as “AA-modified PVA”) is used. AA-PVA is a modified polyvinyl alcohol obtained by reacting polyvinyl alcohol and diketene. The degree of acetoacetylation of AA-modified PVA is preferably in the range of 0.05 to 20 mol%. The protective colloid polyvinyl alcohol may contain other polyvinyl alcohol in addition to AA-PVA. For example, it is desirable to use polyvinyl alcohol that is not acetoacetylated (unmodified polyvinyl alcohol) in combination. By using unmodified polyvinyl alcohol in addition to AA-modified PVA, the reactivity of the vinyl acetate monomer can be increased and the polymerization time can be shortened.

  Examples of the monomer having an acetoacetyl group copolymerized with vinyl acetate monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, allyl alcohol, methacryl alcohol, 2-hydroxy-3-chloropropyl methacrylate, Examples include acetoacetylated products such as 1,4-butylene glycol monoacrylate, 1,4-butylene glycol monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide, and hydroxystyrene.

  The blending amount of the monomer having an acetoacetyl group is desirably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the vinyl acetate monomer. If there are few monomers which have an acetoacetyl group with respect to a vinyl acetate monomer, the water-resistant improvement effect will not fully be acquired. On the contrary, when there are too many monomers which have an acetoacetyl group, the storage stability of an adhesive agent will worsen.

  Emulsion polymerization or emulsion copolymerization of vinyl acetate monomer may be performed using a known reaction aid, polymerization initiator or the like. As the reaction aid, tartaric acid, sodium acetate, sodium carbonate and the like are suitable. As the polymerization initiator, hydrogen peroxide, ammonium persulfate, sodium persulfate and the like are suitable. The protective colloid may be added before or during the polymerization of the vinyl acetate monomer.

(2) Pre-dispersing step This step is a step of preparing a paste by dispersing at least part of the inorganic powder in an aqueous solution (PVA aqueous solution) in which polyvinyl alcohol is dissolved.

  This step may be performed before the polymerization step. That is, the order of the polymerization step and the preliminary dispersion step is not limited. Either step may be performed first, or both steps may proceed simultaneously.

  Examples of the inorganic powder include calcium carbonate, clay, kaolin, titanium oxide, and aluminum hydroxide that are used as pigments and extenders. All of the inorganic powders to be blended may be pasted in this step, but only a part may be pasted. That is, among the inorganic powders to be blended, powders that do not easily remain even if blended directly into the vinyl acetate resin emulsion may be added in a subsequent mixing step without being made into a paste. For example, when one or more selected from calcium carbonate, clay, kaolin, and titanium oxide is used as the inorganic powder, it is desirable that the inorganic powder be made into a paste in this step from the viewpoint of suppressing this occurrence. Especially, when using calcium carbonate, the effect which suppresses this generation | occurrence | production is fully exhibited.

  As the polyvinyl alcohol dissolved in the aqueous solution, AA-PVA, polyvinyl alcohol that is not acetoacetylated (unmodified polyvinyl alcohol), and the like can be used. Either one of these or both may be used. The polyvinyl alcohol may be the same as or different from the polyvinyl alcohol used as the protective colloid.

  For example, polyvinyl alcohol necessary as a component of the adhesive may be divided into a protective colloid and a dispersion medium of inorganic powder. AA-PVA plays a role of improving the water resistance of the adhesive. For this reason, when AA-PVA is used not only as a protective colloid but also as a dispersion medium for inorganic powder, the water resistance of the adhesive can be improved. On the other hand, AA-PVA tends to reduce the polymerizability of the vinyl acetate monomer. For this reason, when a part of AA-PVA is used not as a protective colloid but as a dispersion medium for inorganic powder, the amount of AA-PVA in the reaction system is reduced without changing the total amount of AA-PVA contained in the adhesive. Therefore, the polymerization reaction can be promoted while ensuring water resistance.

  Incidentally, the content ratio of AA-PVA in the adhesive of the present invention is desirably 1% by mass or more and 10% by mass or less. When the content ratio of AA-PVA is less than 1% by mass, the water resistance is lowered. On the contrary, when the content ratio of AA-PVA exceeds 10% by mass, the viscosity increases and the storage stability deteriorates.

  In the polymerization step, when the vinyl acetate monomer is emulsion-polymerized, it is desirable that the polyvinyl alcohol of the PVA aqueous solution contains AA-PVA from the viewpoint of satisfying both the water resistance and heat resistance of the adhesive. In this case, other polyvinyl alcohol may be used in combination with AA-PVA.

  Further, in the polymerization step, when the vinyl acetate monomer and the monomer having an acetoacetyl group are subjected to emulsion copolymerization, desired water resistance and heat resistance can be obtained in the adhesive even if AA-PVA is not included as the polyvinyl alcohol of the PVA aqueous solution. Can be realized. For this reason, the aspect using only unmodified polyvinyl alcohol is employable as PVA aqueous solution. Of course, you may employ | adopt the aspect using only the AA-ized PVA and the mode using both unmodified polyvinyl alcohol and AA-ized PVA.

  Emulsion copolymerization of a vinyl acetate monomer and a monomer having an acetoacetyl group achieves the desired water resistance even when the amount of AA-PVA used is small compared to the case of emulsion polymerization of only a vinyl acetate monomer. can do. For this reason, the usage-amount of AA-ized PVA can be reduced and cost reduction can be aimed at.

  The content ratio of polyvinyl alcohol in the PVA aqueous solution may be appropriately determined in consideration of the viscosity of the aqueous solution, the amount of inorganic powder added, storage stability, and the like. For example, the content ratio of polyvinyl alcohol is preferably 1% by mass or more and 30% by mass or less. When the content ratio of polyvinyl alcohol is less than 1% by mass, the viscosity becomes low and it is difficult to disperse the inorganic powder. In addition, the inorganic powder tends to settle and the storage stability is lowered. On the contrary, when the content rate of polyvinyl alcohol exceeds 30 mass%, a viscosity will become high and the stirring load at the time of paste preparation will become large.

  The PVA aqueous solution may be prepared by heating to about 80 ° C. in consideration of the solubility of polyvinyl alcohol. And after cooling the prepared PVA aqueous solution to about room temperature, an inorganic powder may be added and a paste may be prepared by stirring for a predetermined time.

(3) Mixing step This step is a step of blending the prepared paste into the obtained vinyl acetate resin emulsion and stirring.

  In this step, an adhesive is produced by blending a vinyl acetate resin emulsion with a paste containing inorganic powder. The stirring conditions are not particularly limited. For example, the stirring may be performed at room temperature for about 30 to 60 minutes. In addition to the paste, the remaining inorganic powder, organic pigments, extenders, plasticizers, stabilizers, and the like can be added to the vinyl acetate resin emulsion.

<Adhesive>
The adhesive of the present invention includes a vinyl acetate resin emulsion using polyvinyl alcohol containing acetoacetylated polyvinyl alcohol as a protective colloid and an inorganic powder, and is produced by the production method of the present invention.

  The adhesive of the present invention may contain an organic pigment, an extender, a plasticizer, a stabilizer and the like in addition to the vinyl acetate resin emulsion and the inorganic powder. The adhesive of the present invention is suitable as a highly water-resistant adhesive for wood such as furniture and plywood, paper, and fiber.

  Next, the present invention will be described more specifically with reference to examples.

<Manufacture of the adhesive of an Example>
[Polymerization process (production of vinyl acetate resin emulsion)]
(1) 1st emulsion AA-ized PVA (“Gosefimer (registered trademark) Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 30 parts by mass and unmodified polyvinyl alcohol (manufactured by Electrochemical Industry Co., Ltd. “ B-17 ") and 5 parts by mass were dispersed in 390 parts by mass of water and dissolved by stirring at 80 ° C for 1 hour. After adding 6 parts by weight of a 10% aqueous solution of tartaric acid and 1 part by weight of a 1.4% aqueous solution of hydrogen peroxide to this aqueous solution, 307 parts by weight of a vinyl acetate monomer and a 1.4% aqueous solution of hydrogen peroxide 9 parts by mass was added dropwise over 3 hours to carry out emulsion polymerization. After polymerization, the mixture was aged at 80 ° C. for 1 hour, and then cooled to obtain a vinyl acetate resin emulsion having an acetoacetyl group (resin content: 46%). The obtained vinyl acetate resin emulsion is referred to as a first emulsion.

(2) Second emulsion 7 parts by mass of AA-PVA (same as above) and 28 parts by mass of unmodified polyvinyl alcohol (same as above) are dispersed in 390 parts by mass of water and dissolved by stirring at 80 ° C. for 1 hour. did. After adding 6 parts by weight of a 10% aqueous solution of tartaric acid and 1 part by weight of a 1.4% aqueous solution of hydrogen peroxide to this aqueous solution, 293 parts by weight of vinyl acetate monomer and 2-acetoacetoxyethyl methacrylate (AAEM) 14 parts by mass and 9 parts by mass of a 1.4% aqueous solution of hydrogen peroxide were added dropwise in 3 hours to carry out emulsion copolymerization. After polymerization, the mixture was aged at 80 ° C. for 1 hour, and then cooled to obtain a vinyl acetate resin emulsion having an acetoacetyl group (resin content: 46%). The obtained vinyl acetate resin emulsion is referred to as a second emulsion.

[Pre-dispersion step (paste preparation)]
(1) First paste 15 parts by mass of AA-modified PVA (same as above) was dispersed in 85 parts by mass of water and dissolved by stirring at 80 ° C. for 1 hour. After cooling this solution to about room temperature, 150 parts by weight of heavy calcium carbonate powder (average particle size 2 μm) was added and stirred for 30 minutes to prepare a paste. The obtained paste is referred to as a first paste.

(2) Second paste
15 parts by mass of unmodified polyvinyl alcohol (same as above) was dispersed in 85 parts by mass of water and dissolved by stirring at 80 ° C. for 1 hour. After cooling this solution to about room temperature, 150 parts by weight of heavy calcium carbonate powder (same as above) was added and stirred for 30 minutes to prepare a paste. The obtained paste is referred to as a second paste.

[Mixing process]
Four types of adhesives of Examples 1 to 3 and Reference Example 1 were appropriately combined with the produced vinyl acetate resin emulsion (first and second emulsions) and the prepared pastes (first and second pastes). Manufactured. The adhesive was produced by adding a paste to the vinyl acetate resin emulsion and stirring for 30 minutes. In any combination, an adhesive having a good dispersion state of the heavy calcium carbonate powder was obtained without occurrence of residue. The composition of each adhesive is summarized in Table 1 below.

<Manufacture of adhesive of comparative example>
[Comparative Example 1]
150 parts by weight of heavy calcium carbonate powder (same as above) was directly added to the produced second emulsion. However, the added powder remains so that a usable adhesive could not be produced.

[Comparative Example 2]
Instead of the vinyl acetate resin emulsion produced, a vinyl acetate resin emulsion containing no acetoacetyl group (“A-322K” (45% resin content) manufactured by Aika Industry Co., Ltd.) is used to produce an adhesive. did. Specifically, the prepared second paste was added to a vinyl acetate resin emulsion containing no acetoacetyl group and stirred for 30 minutes.

<Evaluation of adhesive>
[Test method]
The adhesiveness of each adhesive in Examples and Comparative Examples was evaluated by the following test methods. First, at 23 ° C., uniformly apply 90 g / m ^{2 of} adhesive on each side of each of two lauan plywoods (equivalent to JAS1 class, 5 ply, 12 mm, formaldehyde emission amount F ☆☆☆☆). The plywood was bonded together. The deposition time was set within 30 minutes, and then the specimen was pressed at 0.5 MPa for 30 minutes to produce a specimen. Then, JAS (Japanese Agricultural Standards) specially processed decorative plywood type 1 and type 2 immersion peel tests were conducted to confirm the presence or absence of peeling.

[Test results]
Table 1 summarizes the composition of each adhesive and the evaluation results. In Table 1, with respect to adhesiveness, no peeling is indicated by a circle, and peeling is indicated by an x mark.

  As described above, in Examples 1 to 3, Reference Example 1 and Comparative Example 2 manufactured using a paste in which heavy calcium carbonate powder was dispersed in a PVA aqueous solution, heavy calcium carbonate powder was uniformly dispersed. An adhesive was obtained. On the other hand, in Comparative Example 1, since the heavy calcium carbonate powder was directly added to the vinyl acetate resin emulsion, an adhesive could not be produced.

  In addition, as shown in Table 1, the test specimens using the adhesives of Examples 1 to 3 manufactured by the manufacturing method of the present invention were peeled off in any of the type 1 and type 2 peeling tests. There wasn't. However, the specimen using the adhesive of Reference Example 1 was not peeled off in the Type 2 immersion peel test, but was peeled off in the Type 1 immersion peel test. The vinyl acetate resin emulsion in the adhesive of Reference Example 1 is manufactured without using a monomer having an acetoacetyl group (AAEM), and the paste does not contain AA-PVA. For this reason, it is considered that the content of the acetoacetyl group is reduced and the water resistance is lowered.

Claims (7)

A method for producing an adhesive comprising a vinyl acetate resin emulsion and an inorganic powder,
Polymerization to obtain vinyl acetate resin emulsion by emulsion polymerization of vinyl acetate monomer using polyvinyl alcohol containing acetoacetylated polyvinyl alcohol as protective colloid, or emulsion copolymerization of vinyl acetate monomer and monomer having acetoacetyl group Process,
A preliminary dispersion step of preparing a paste by dispersing at least a part of the inorganic powder in an aqueous solution in which polyvinyl alcohol containing acetoacetylated polyvinyl alcohol is dissolved;
Mixing step of blending the prepared paste into the obtained vinyl acetate resin emulsion and stirring;
The manufacturing method of the adhesive agent characterized by having. The said polyvinyl alcohol used in the said pre-dispersion process is a manufacturing method of the adhesive agent of Claim 1 containing the polyvinyl alcohol which is not acetoacetylated. The method for producing an adhesive according to claim 1 or 2, wherein the polyvinyl alcohol used as the protective colloid in the polymerization step includes polyvinyl alcohol that is not acetoacetylated. The said inorganic powder disperse | distributed to the said aqueous solution in the said pre-dispersion process is 1 or more types chosen from a calcium carbonate, a clay, a kaolin, and a titanium oxide, The manufacture of the adhesive agent in any one of Claim 1 thru | or 3 Method. The method for producing an adhesive according to claim 4 , wherein the inorganic powder dispersed in the aqueous solution is calcium carbonate in the preliminary dispersion step. The method for producing an adhesive according to any one of claims 1 to 5, wherein a content ratio of the acetoacetylated polyvinyl alcohol in the adhesive is 1% by mass or more and 10% by mass or less. A vinyl acetate resin emulsion using polyvinyl alcohol containing acetoacetylated polyvinyl alcohol as a protective colloid and an inorganic powder, and produced by the production method according to any one of claims 1 to 6. Adhesive.