JP4675087B2 - Method for producing vinyl acetate resin emulsion, vinyl acetate resin emulsion prepared by the production method, and aqueous adhesive - Google Patents

Description

  The present invention relates to a method for producing a vinyl acetate resin emulsion useful as an adhesive, a paint base, a coating agent, etc., a vinyl acetate resin emulsion prepared by the method for producing a vinyl acetate resin emulsion, and the vinyl acetate resin. The present invention relates to an aqueous adhesive containing an emulsion.

  Conventionally, vinyl acetate resin emulsions are widely used for adhesives, paint bases and coating agents for woodworking, paper processing, fiber processing and the like. However, since the minimum film-forming temperature is high as it is, in many cases, it is necessary to add film-forming aids such as volatile plasticizers and organic solvents. Phthalic acid esters are used as the plasticizer, but there are indications that phthalic acid esters are unfavorable to the environment due to the recent increase in environmental problems. Is being considered. However, plasticizers are essentially VOC (Volatile Organic Compounds), and in particular for adhesives used in housing, the VOC component may be a causative agent for new building disease (sick house syndrome). There is also a way of thinking. Thus, even if it is a water-based adhesive with little environmental impact, the VOC problem resulting from a plasticizer is pointed out. Therefore, a vinyl acetate resin emulsion adhesive not containing a plasticizer has been studied.

  For example, an adhesive for woodworking containing a vinyl acetate resin emulsion obtained by seed-polymerizing vinyl acetate in an ethylene vinyl acetate copolymer resin emulsion having an ethylene content of 15 to 35% by mass has been proposed (Patent Document 1). reference). Further, in a method for producing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, a step of performing seed polymerization while adding vinyl acetate into the system, As a pre-process or post-process of the process, a polymerizable unsaturated monomer other than vinyl acetate is added to the system, or a polymerizable unsaturated monomer other than vinyl acetate is added to the vinyl acetate during the process. A method for producing a vinyl acetate resin emulsion including a step of independently adding it into the system has been proposed (see Patent Documents 2 and 3).

  The vinyl acetate resin emulsions obtained by these production methods have improved low-temperature adhesive strength during low-temperature curing, and when a film is formed at room temperature (about 23 ° C.), a transparent film can be obtained. In particular, the low-temperature film formability measured according to JIS K6804 is good, and with this measurement method, a transparent film is formed.

  Furthermore, as a method for producing a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate, the copolymer in the ethylene-vinyl acetate copolymer emulsion is used as a seed in the presence of a protective colloid of polyvinyl alcohol. In the method for producing a vinyl acetate resin emulsion in which vinyl acetate monomer is added dropwise to perform seed polymerization, 3 to 15% by mass of vinyl acetate monomer to be polymerized and 15 to 30% by mass of a specified amount of polymerization initiator %, A core-shell type emulsion using a vinyl acetate monomer and an acrylic acid monomer using a polyvinyl alcohol resin as a protective colloid When performing polymerization, the vinyl acetate monomer is used to form the core Perform emulsion polymerization, followed has been proposed a method of producing vinyl acetate resin emulsion for performing emulsion polymerization of the shell portion with a mixture of vinyl acetate monomer and acrylic acid-based monomer (see Patent Document 5).

  Further, a polyvinyl acetate emulsion containing a polyvinyl alcohol containing 2 to 12% by mass with respect to the solid content and containing no plasticizer or containing 5% by mass or less of the plasticizer with respect to the solid content. An adhesive composition containing an aqueous latex other than an emulsion has been proposed (see Patent Document 6). As described above, the adhesive in which the aqueous latex is blended with the vinyl acetate resin emulsion is not low-temperature curing because the vinyl acetate resin emulsion is not seed-polymerized in the ethylene-vinyl acetate copolymer resin emulsion. The low-temperature adhesion strength at the time is low, and the film-forming property is also low, and the low-temperature film-forming property measured according to JIS K6804 is particularly low.

  An adhesive composition in which an ethylene / vinyl acetate copolymer resin emulsion having a glass transition point of −10 ° C. or less is blended with a vinyl acetate resin emulsion, a vinyl acetate resin emulsion, and a film forming temperature of 0 ° C. or less. Adhesive compositions in which an acrylic copolymer resin emulsion is mixed have also been proposed (see Patent Document 7 to Patent Document 8), but these adhesives or emulsions have adhesive strength, water resistance, and heat resistance. Is not always enough.

JP-A-11-92734 JP 2000-239307 A JP 2000-302809 A JP 2001-131206 A JP 2001-302709 A Japanese Patent Laid-Open No. 11-279507 JP 2001-294833 A JP 2003-176468 A

  However, when vinyl acetate resin emulsion is obtained by seed polymerization of vinyl acetate in ethylene-vinyl acetate copolymer resin emulsion, the viscosity becomes extremely high during cooling after seed polymerization, making it difficult to use. Or immediately after removal from the reaction vessel, the entire liquid aggregates into a gel state, or immediately after removal from the reaction vessel is in a good state, but thickens during storage and becomes difficult to use. In some cases, it is difficult to produce a vinyl acetate resin emulsion having good stability.

Accordingly, an object of the present invention is to provide a vinyl acetate resin emulsion capable of producing a vinyl acetate resin emulsion having good stability by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion. And a vinyl acetate resin emulsion prepared by the production method, and an aqueous adhesive.
Another object of the present invention is to provide excellent low-temperature film formability and high adhesive strength even under seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion under mild conditions. Vinyl acetate resin capable of producing a vinyl acetate resin emulsion that exhibits high adhesion strength (low temperature adhesion strength) even during curing, can form a transparent film, and has good stability It is in providing the manufacturing method of a system emulsion, the vinyl acetate resin system emulsion prepared by this manufacturing method, and an aqueous adhesive.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention used a seed polymerization in preparing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion. Vinyl acetate having good stability when the blending amount of vinyl acetate during polymerization (particularly in the initial stage of polymerization) is a specific ratio with respect to the gel fraction of the ethylene-vinyl acetate copolymer resin emulsion used. It has been found that a resin emulsion can be obtained. The present invention has been completed based on these findings.

That is, the present invention is a method for producing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, and all vinyl acetate is introduced into a reaction system. The ratio (X) of vinyl acetate to be introduced by 25% of the time required to the total amount of vinyl acetate introduced and the gel fraction (Y) of the ethylene-vinyl acetate copolymer resin emulsion are as follows: Seed polymerization of vinyl acetate by introducing vinyl acetate into the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass under the conditions of (a) or (b). the method of manufacturing poly (vinyl acetate) emulsion, wherein the proviso that the gel fraction (Y) is an ethylene - vinyl acetate copolymer resin emulsion, on a fluorine-based resin sheet, the thickness after drying After coating with a coating amount of (film thickness) of 200 μm, after drying at room temperature (20-25 ° C.) to obtain a film with an ethylene-vinyl acetate copolymer resin emulsion, this film is cut finely, In an atmosphere of 50 ° C., the film is immersed in 100 times the amount of toluene (referred to as “W ¹ ”), treated for 5 hours, and then filtered through a 200 mesh wire mesh. The filtration residue was washed with toluene and dried to obtain a toluene insoluble matter (mass is “W ² ”), which was obtained by the following formula.
Gel fraction (wt%) = provide ^{(W 2 / W 1) ×} 100].
(A): When the ratio (X) is 5% by mass or more and less than 10% by mass, the gel fraction (Y) is 40% by mass or more. (B): The ratio (X) is 10% by mass or more and 25 When it is less than mass%, the gel fraction (Y) is 15 mass% or more.

In the method for producing a vinyl acetate resin emulsion of the present invention, vinyl acetate is converted into the following methods (i) to (%) for a period of time up to 25% of the time required to introduce all the vinyl acetate into the reaction system. It is preferably introduced into the reaction system by any one of methods iii).
(I): A predetermined amount of vinyl acetate is introduced into the reaction system dropwise while seed polymerization is performed. (Ii): A predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization. ): A part of vinyl acetate in a predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization, and the remaining vinyl acetate is introduced into the reaction system by dropwise addition while performing seed polymerization. Do

  In the present invention, the ratio (X) is preferably 10% by mass or more and 20% by mass or less.

  The present invention is also a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, which is prepared by the method for producing the vinyl acetate resin emulsion. A vinyl acetate resin emulsion is provided.

  The present invention is further an aqueous adhesive comprising a vinyl acetate resin emulsion, wherein the vinyl acetate resin emulsion is a vinyl acetate resin emulsion prepared by the method for producing a vinyl acetate resin emulsion. An aqueous adhesive is provided.

  In the present specification, “acryl” and “methacryl” may be collectively referred to as “(meth) acryl”, “acryloyl” and “methacryloyl” may be collectively referred to as “(meth) acryloyl”, and the like.

  According to the method for producing a vinyl acetate resin emulsion of the present invention, a vinyl acetate resin emulsion having good stability is produced by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion. Can do. Therefore, a vinyl acetate resin-based emulsion that does not contain a plasticizer at all or has a reduced amount of plasticizer used can be obtained with good stability. Moreover, even if seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion is performed under mild conditions, it has excellent low-temperature film formability and high adhesive strength, and high adhesion even during low-temperature curing. While exhibiting strength (low-temperature adhesive strength), a transparent film can be formed, and a vinyl acetate resin emulsion having good stability can be produced. Therefore, this vinyl acetate resin-based emulsion is useful as a component of an aqueous adhesive.

The method for producing a vinyl acetate resin emulsion according to the present invention is a method for producing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion. The ratio of vinyl acetate introduced to the total amount of vinyl acetate introduced by 25% of the time required for introduction into the inside (X) and the gel fraction of the ethylene-vinyl acetate copolymer resin emulsion (Y) And vinyl acetate is introduced into the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass under the following conditions (a) or (b). It is characterized by seed polymerization of vinyl.
(A): When the ratio (X) is 5% by mass or more and less than 10% by mass, the gel fraction (Y) is 40% by mass or more (preferably 45% by mass or more, more preferably 45% by mass to 90% by mass). (B): When the ratio (X) is 10 mass% or more and less than 25 mass%, the gel fraction (Y) is 15 mass% or more (preferably 17 mass% or more, more preferably 17 mass%). % To 90% by mass)

  Thus, in the method for producing a vinyl acetate resin emulsion according to the present invention, the total amount of vinyl acetate introduced into vinyl acetate by 25% of the time required to introduce all vinyl acetate into the reaction system. The ratio (X) with respect to the amount is 5 mass% or more and less than 25 mass%, and the amount of vinyl acetate introduced in the initial stage of polymerization (initial stage where the polymerization rate is less than 25 mass%) Since it is less than the case where it is added dropwise at a certain ratio (in this case, the ratio (X) is 25% by mass), an ethylene-vinyl acetate copolymer resin emulsion (“E-PVac emulsion”) In some cases, the vinyl acetate introduced in the initial stage of the polymerization is introduced by dropping at a constant rate from the beginning to the end. Increases the rate present on the seed particles by emulsion particles -PVac emulsion, on the seed particles, effectively it seems capable of polymerizing vinyl acetate. That is, conversely, the proportion present in water away from the seed particles is reduced, and the proportion of vinyl acetate polymer polymerized outside the seed particles (which is a normal vinyl acetate resin) can be reduced. I think I can do it. Therefore, the obtained vinyl acetate resin emulsion (sometimes referred to as “PVac emulsion”) has excellent low-temperature film-forming properties and high adhesive strength, and has high adhesive strength (low-temperature adhesive strength) even during low-temperature curing. )), A transparent film can be formed, and storage stability is also good. The low-temperature film formability is measured according to JIS K6804.

  In the polymerization of vinyl acetate, if seed polymerization does not occur and the polymerization is performed outside the seed particles, it becomes a normal vinyl acetate resin emulsion, and in this case, the minimum film-forming temperature is increased and formed. The transparency of the applied film is reduced.

  Moreover, since the gel fraction (Y) of the E-PVac emulsion used in the seed polymerization is defined as in the condition (a) or (b) with respect to the ratio (X) (specifically In the case where the ratio (X) is 5% by mass or more and less than 10% by mass, an E-PVac emulsion having a gel fraction (Y) of 40% by mass or more is used, and the ratio (X) is 10% by mass. When the amount is less than 25% by mass, since an E-PVac emulsion having a gel fraction (Y) of 15% by mass or more is used), a PVac emulsion having good stability (particularly storage stability) is obtained. Can do. As described above, when the gel fraction (Y) of the E-PVac emulsion used is high, the graft ratio of the E-PVac emulsion particles and the protective colloid is increased, so that the particles obtained by sheet polymerization of vinyl acetate are also obtained. It seems that the stability of PVac emulsion is good because it can exist stably. When the amount of vinyl acetate introduced in the initial stage of polymerization decreases, the proportion of seed polymerization on the emulsion particles of the E-PVac emulsion decreases, and the polymerization reaction proceeds in a reaction field other than the seed particles. Stability is likely to decrease.

  In particular, in the present invention, since vinyl acetate is introduced into the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass, all vinyl acetate is introduced into the reaction system. The amount of vinyl acetate introduced by 25% of the time required is the case where vinyl acetate is introduced into the reaction system at a constant rate (in this case, the ratio (X) is 25 as described above. Therefore, the vinyl acetate seed polymerization in the E-PVac emulsion can be performed under milder conditions, and the vinyl acetate seed polymerization can be easily controlled. .

  Of course, since the PVac emulsion is obtained by seed polymerization of vinyl acetate in the E-PVac emulsion, it has excellent film formability on various substrates at room temperature (about 23 ° C.) and is a transparent film. Is obtained.

  Thus, in the present invention, since vinyl acetate is seed-polymerized in the E-PVac emulsion to obtain the PVac emulsion, the E-PVac emulsion is used as the seed emulsion (that is, E as the seed particles). -Emulsion particles in PVac emulsion are used, and ethylene-vinyl acetate copolymer resin in E-PVac emulsion is used as a seed polymer)

  In the method for producing a vinyl acetate resin emulsion of the present invention, the PVac emulsion is an E-PVac emulsion, and the ratio (X) is 5% by mass or more under the conditions satisfying the condition (a) or (b). It can be produced by a method for producing a vinyl acetate resin emulsion comprising a step of introducing vinyl acetate into a reaction system so as to be less than 25% by mass and seed polymerizing vinyl acetate to obtain a PVac emulsion. . Thus, in the present invention, the ratio (X) of vinyl acetate introduced by 25% of the time required to introduce all the vinyl acetate into the reaction system is 5% by mass with respect to the total introduced amount of vinyl acetate. More than and less than 25% by mass, and the gel fraction (Y) of the E-PVac emulsion with respect to the ratio (X) is specified, and the time required to introduce all the vinyl acetate into the reaction system After the lapse of 25%, there is no particular limitation as long as the remaining vinyl acetate can be introduced into the reaction system to perform seed polymerization.

  The ratio (X) is not particularly limited as long as it is 5% by mass or more and less than 25% by mass, but is preferably 8% by mass or more and 23% by mass or less, particularly 10% by mass or more and 20% by mass. % Or less is preferable.

Therefore, the method for producing a vinyl acetate resin emulsion of the present invention includes the following steps (A) and (B).
Step (A): In the ethylene-vinyl acetate copolymer resin emulsion, up to 25% of the time required to introduce all the vinyl acetate into the reaction system, the conditions (a) or ( Under the conditions satisfying b), the ratio (X) of vinyl acetate introduced to the total amount of vinyl acetate introduced by 25% of the time required to introduce all the vinyl acetate into the reaction system is 5 masses. The step of introducing vinyl acetate into the reaction system so as to be not less than 25% and less than 25% by mass and seed polymerization of vinyl acetate Step (B): In the time required to introduce all the vinyl acetate into the reaction system In contrast, after 25% of time has elapsed, the remaining vinyl acetate is introduced into the reaction system, and vinyl acetate is seed-polymerized.

Step (A) is a step from the start of introducing vinyl acetate into the reaction system up to a time of 25% with respect to the time required to introduce all the vinyl acetate into the reaction system. The time point (time) at which 25% of the time required to introduce all the vinyl acetate into the reaction system after starting to introduce vinyl acetate into the reaction system is included in the step (A). . In the step (A), vinyl acetate is used in the E-PVac emulsion so that the ratio (X) is 5% by mass or more and less than 25% by mass under the conditions satisfying the condition (a) or (b). Is introduced into the reaction system to seed polymerize vinyl acetate. In the step (A), the method of introducing vinyl acetate into the reaction system is not particularly limited, and a method of adding all the amounts of vinyl acetate to be introduced into the reaction system by adding them all at once, dropwise addition For example, a method of introducing by continuous or intermittent addition, a method of combining these, and the like can be mentioned. More specifically, the vinyl acetate is one of the following methods (i) to (iii) within a period of up to 25% of the time required to introduce all the vinyl acetate into the reaction system. It is preferable to introduce into the reaction system by any method.
(I): A predetermined amount of vinyl acetate is introduced into the reaction system dropwise while seed polymerization is performed. (Ii): A predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization. ): A part of vinyl acetate in a predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization, and the remaining vinyl acetate is introduced into the reaction system by dropwise addition while performing seed polymerization. Do

  In addition, in said (i) and (iii), when introduce | transducing vinyl acetate in a reaction system by dripping, it can be dripped continuously or intermittently (especially continuously). Therefore, it may be dropped by any of the continuous dropping method and the intermittent dropping method, and it is particularly preferable to drop by the continuous dropping method.

  In the present invention, it is preferable to introduce a predetermined amount of vinyl acetate into the reaction system at least partially by dropwise addition from the viewpoint of easy control of the reaction. Therefore, the introduction method (i) or (iii) is preferable, and the introduction method (i) can be particularly preferably employed.

  On the other hand, in the step (B), after 25% of the time required to introduce all the vinyl acetate into the reaction system has elapsed, all the vinyl acetate has been completely introduced into the reaction system. It is a process. The time point (time) at which all the vinyl acetate is completely introduced into the reaction system is included in the step (B). In step (B), after the step (A), the remaining vinyl acetate is introduced into the reaction system, and vinyl acetate is seed-polymerized. In the step (B), the method of introducing vinyl acetate into the reaction system is not particularly limited, but from the viewpoint of easy control of the reaction, the remaining vinyl acetate is seeded while the reaction system is dropped. The method of introducing into the reaction system can be suitably employed depending on the method of introducing into the reaction system. In this case, the remaining vinyl acetate can be introduced into the reaction system by a continuous dropping method or an intermittent dropping method (particularly, a continuous dropping method).

  In the present invention, “the time required to introduce all the vinyl acetate into the reaction system” means that after all vinyl acetate has been introduced into the reaction system, all the vinyl acetate has been introduced into the reaction system. Although it can be a time required, it is important that the time during which the vinyl acetate is effectively seed-polymerized during this time. Therefore, “time required to introduce all the vinyl acetate into the reaction system” includes, for example, the seed polymerization of vinyl acetate between the start of introduction of vinyl acetate into the reaction system and the completion of the introduction. Aging is performed during the time during which the temperature in the reaction system is increased to the polymerization start temperature at which the polymerization starts, longer intervals than necessary when vinyl acetate is intermittently introduced into the reaction system, and during the reaction. The time during the day is not included. As described above, when vinyl acetate is intermittently introduced into the reaction system, the interval between intermittent introductions is usually long, but most of the vinyl acetate already introduced into the reaction system is reacted. If the time is longer than that, or if the time is unnecessarily long, the time is longer than necessary when intermittently introducing vinyl acetate into the reaction system. It is not included in the “time required for introduction into the reaction system”.

  Specifically, the “time required to introduce all the vinyl acetate into the reaction system” is 25% of the time required to introduce all the vinyl acetate into the reaction system. (1) When introducing vinyl acetate into the reaction system by the introduction method (i), the time required to introduce all the vinyl acetate into the reaction system after starting to introduce vinyl acetate dropwise. (2) When vinyl acetate is introduced into the reaction system by the introduction method (ii), the time required to introduce all the vinyl acetate into the reaction system from the start of the reaction (3) When vinyl acetate is introduced into the reaction system by the introduction method (iii), among the time when the reaction starts to be started or the time when vinyl acetate is started to be introduced dropwise, Izu From the earlier time points or may be a time required to introduce the vinyl acetate in all the reaction system. Therefore, the time required to introduce all the vinyl acetate into the reaction system was started when the reaction was started or vinyl acetate was introduced dropwise according to the introduction methods (i) to (iii). It can be calculated starting from time.

  Further, “25% of the time required to introduce all of vinyl acetate into the reaction system” refers to the time after starting the reaction according to the introduction methods (i) to (iii) or The time at which the vinyl acetate starts to be introduced dropwise can be 25% of the time required to introduce all the vinyl acetate into the reaction system. For example, a specific example of an example in which vinyl acetate is introduced into the reaction system by the introduction method (i) will be described in which all vinyl acetate is introduced into the reaction system after the vinyl acetate starts to be introduced dropwise. When the time required is 2 hours, “25% of the time required to introduce all the vinyl acetate into the reaction system” is 30 minutes after the vinyl acetate is introduced dropwise.

  Thus, “25% of the time required to introduce all the vinyl acetate into the reaction system” can be obtained unless all the vinyl acetate is actually introduced into the reaction system. However, when vinyl acetate is seed-polymerized, a reaction plan is usually made in advance, such as how to introduce vinyl acetate into the reaction system and how long it is allowed to react. Therefore, it can be easily obtained from the reaction plan.

  In addition, when manufacturing a PVac emulsion by seed polymerization of vinyl acetate, aging is usually performed after the introduction of vinyl acetate into the reaction system. Such aging is performed after the introduction of vinyl acetate. Therefore, the time required for this aging is not included in the “time required for introducing all the vinyl acetate into the reaction system”.

(E-PVac emulsion)
The E-PVac emulsion (ethylene-vinyl acetate copolymer resin-based emulsion) used in the present invention is a vinyl acetate emulsion introduced up to 25% of the time required to introduce all of vinyl acetate into the reaction system. The gel fraction (Y) is defined according to the ratio (X) to the total amount of vinyl acetate introduced. Specifically, as the E-PVac emulsion, when the ratio (X) is 5% by mass or more and less than 10% by mass, an E-PVac emulsion having a gel fraction (Y) of 40% by mass or more is used. Moreover, when the ratio (X) is 10% by mass or more and less than 25% by mass, an E-PVac emulsion having a gel fraction (Y) of 15% by mass or more is used.

In the present invention, the gel fraction (Y) of the E-PVac emulsion can be determined as follows. An ethylene-vinyl acetate copolymer resin emulsion was applied on a fluororesin plate in a coating amount so that the thickness (film thickness) after drying was 200 μm, and then dried at room temperature (20 to 25 ° C.). After obtaining a film of an ethylene-vinyl acetate copolymer resin emulsion, the film is cut into fine pieces, and the finely cut form of the film is measured under the atmosphere of 50 ° C. (the weight of the film). by immersing in 100 volumes of toluene relative to "W ^1"), for 5 hours, then filtered through a 200-mesh metal gauze, Thereafter, washing the filter residue on the wire mesh with toluene drying the resultant to obtain insoluble toluene insoluble matter in toluene (the mass of toluene-insoluble matter and "W ^2"), the following equation, ethylene - vinyl acetate copolymer resin Determining gel fraction of the emulsion (mass%).
Gel fraction (mass%) = (W ² / W ¹ ) × 100

  In the E-PVac emulsion, the ethylene-vinyl acetate copolymer resin is not particularly limited, but usually a copolymer having an ethylene content of about 5 to 60% by mass is used. Among them, as the ethylene-vinyl acetate copolymer resin in the E-PVac emulsion, an ethylene-vinyl acetate copolymer resin having an ethylene content in the range of 15 to 35% by mass gives particularly low film formation temperature, This is preferable because it also provides excellent adhesive strength.

  In addition, vinyl acetate content in the ethylene-vinyl acetate copolymer resin in E-PVac emulsion is about 40-95 mass% normally (preferably 65-85 mass%). The ethylene-vinyl acetate copolymer resin in the E-PVac emulsion contains a crosslinkable monomer as a monomer component at a content of about 0 to 10% by mass.

  In the E-PVac emulsion, the ethylene-vinyl acetate copolymer resins may be used alone or in combination of two or more.

  Ethylene-vinyl acetate copolymer resin emulsions used as E-PVac emulsions are widely commercially available and can be easily obtained in the market. A commercially available ethylene-vinyl acetate copolymer resin emulsion can be used as an E-PVac emulsion by adjusting the concentration by dilution with water as required.

  The E-PVac emulsion may be an emulsion prepared by dispersing in advance a polymer obtained by polymerization (polymer used as a seed polymer) in water, or an emulsion produced by emulsion polymerization (a heavy polymer used as a seed polymer). Emulsion containing coalescence). The E-PVac emulsion may be an emulsion prepared in the preceding stage in a multistage polymerization in which the step of preparing a seed emulsion by emulsion polymerization is performed in the previous stage and the step of performing seed polymerization in the seed emulsion is performed in the subsequent stage. The vinyl acetate resin emulsion of the present invention can also be produced by a series of polymerizations such as multistage polymerization.

  In the seed polymerization, the amount of E-PVac emulsion used is not particularly limited. As the E-PVac emulsion, for example, the amount (solid content) of ethylene-vinyl acetate copolymer resin (seed polymer) in the E-PVac emulsion is the total amount in the vinyl acetate resin emulsion (PVac emulsion) obtained by seed polymerization. The amount is desirably about 10 to 60% by mass (preferably 15 to 40% by mass, more preferably 15 to 30% by mass) with respect to the resin content (total solid content). If the use amount (solid content) of the E-PVac emulsion is less than 10% by mass with respect to the total resin content (total solid content) in the PVac emulsion, sufficient film formability may not be exhibited. On the other hand, if the amount exceeds 60% by mass, the final adhesive strength decreases.

  The E-PVac emulsion may be an E-PVac emulsion made of an ethylene-vinyl acetate copolymer resin having a glass transition temperature (Tg) of 0 ° C. or lower (for example, 0 to −15 ° C.). It may be an E-PVac emulsion with an ethylene-vinyl acetate copolymer resin exceeding ℃. As the E-PVac emulsion, an E-PVac emulsion made of an ethylene-vinyl acetate copolymer resin having a glass transition temperature (Tg) of 5 ° C. or lower (for example, 5 to −15 ° C., preferably 0 to −15 ° C.) is suitably used. Can be used. In the present invention, even when an ethylene-vinyl acetate copolymer resin emulsion based on an ethylene-vinyl acetate copolymer resin having a Tg of greater than 0 ° C. is used as the E-PVac emulsion, the low-temperature film formability is good. .

(Monomer component)
In the present invention, seed polymerization can be carried out in the presence of a polymerization initiator in an aqueous emulsion containing the E-PVac emulsion and preferably a protective colloid. In the seed polymerization, a polymerizable unsaturated monomer other than vinyl acetate (sometimes referred to as “other monomer”) may be used as a monomer component. Examples of such other monomers include, but are not limited to, (meth) acrylic acid esters (acrylic acid esters and methacrylic acid esters), vinyl esters, vinyl ethers, aromatic vinyl compounds, unsaturated carboxylic acids, and the like. Examples include acid amides, olefins, dienes, and unsaturated nitriles. Other monomers can be used alone or in combination of two or more.

In other monomers, as the (meth) acrylic acid esters, any of conventionally known (meth) acrylic acid esters can be used. Typical examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meth) acrylic acid alkyl esters such as octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate [preferably (meth) acrylic acid C _1-18 Alkyl ester, more preferably (meth) acrylic acid C _1-14 alkyl ester]; hydroxyalkyl (meth) acrylate such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, methoxy (meth) acrylate (Meth) acrylic acid such as methyl and ethoxymethyl (meth) acrylate Examples include reactive functional group-containing (meth) acrylic acid esters such as lucoxyalkyl and glycidyl (meth) acrylate.

As vinyl esters, any conventionally known vinyl ester other than vinyl acetate can be used. As typical examples, for example, vinyl formate; vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl octylate, Veova 10 (trade name: Shell Japan Co., Ltd.) C _3-18 aliphatic carboxylic acid vinyl ester; vinyl benzoate vinyl aromatic carboxylate and the like.

  Any conventionally known vinyl ethers can be used as the vinyl ethers. Typical examples include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-propyl vinyl ether, n-butyl vinyl ether, sec-butyl vinyl ether, tert-butyl vinyl ether, and tert-amyl vinyl ether. .

  Examples of the aromatic vinyl compound include styrene, vinyl toluene, α-methyl styrene, N-vinyl pyrrolidone, vinyl pyridine and the like. Unsaturated carboxylic acid amides include (meth) acrylamides such as (meth) acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, and N-methoxybutylacrylamide. Examples of olefins include ethylene, propylene, butylene, isobutylene, and pentene. Examples of dienes include butadiene, isoprene, chloroprene and the like. Moreover, (meth) acrylonitrile etc. are mentioned as unsaturated nitriles.

In addition, as another monomer, at least 1 sort (s) selected from acrylic acid esters, methacrylic acid esters, vinyl esters, and vinyl ethers can be used suitably. Other monomers include, in particular, (meth) acrylic acid alkyl esters [eg (meth) acrylic acid C _1-18 alkyl esters, especially (meth) acrylic acid C _1-14 alkyl esters], C _3-14 aliphatics. Carboxylic acid vinyl esters are preferred because they have the least decrease in low temperature adhesive strength during low temperature curing. In addition to its low-temperature adhesion strength, from the standpoint of maintaining excellent low-temperature film-forming performance (low-temperature film-forming performance), other monomers include acrylic acid C _3-12 alkyl esters and methacrylic acid C _2- More preferred are ₈ alkyl esters.

  In the present invention, a monomer component such as vinyl acetate or a mixed monomer is introduced and introduced into the reaction system by 25% of the time required to introduce all the vinyl acetate into the reaction system. The ratio (X) of the vinyl acetate to be introduced to the total amount of vinyl acetate introduced is not particularly limited as long as it is 5% by mass or more and less than 25% by mass. For example, as described above, the vinyl acetate as the monomer component is used in the introduction methods (i) to (iii) up to 25% of the time required to introduce all the vinyl acetate into the reaction system. ) Can be introduced into the reaction system, and after 25% of the time required to introduce all the vinyl acetate into the reaction system, The remaining vinyl acetate can be introduced into the reaction system by a method of introducing it into the reaction system dropwise while seed polymerization. As a method for introducing vinyl acetate into the reaction system, the ratio (X) is a predetermined amount up to 25% of the time required to introduce all the vinyl acetate into the reaction system. Was introduced into the reaction system by continuously dropwise addition while seed polymerization, while 25% of the time required to introduce all the vinyl acetate into the reaction system had elapsed. After the time, a method of introducing the remaining vinyl acetate into the reaction system by continuously adding dropwise while performing seed polymerization is preferable.

  The amount of vinyl acetate used for seed polymerization is, for example, 10 to 90% by mass (preferably 15 to 80% by mass, further based on the total resin (total solid content) of the vinyl acetate resin emulsion obtained by seed polymerization. Preferably it is about 40-80 mass%).

  In addition, when other monomer components (polymerizable unsaturated monomers other than vinyl acetate) are used as the monomer component, there are no particular restrictions on the method of adding and introducing other monomers into the reaction system. And a method of adding and introducing into the reaction system as a mixture mixed with vinyl acetate (sometimes referred to as “mixed monomer”), a method of adding and introducing into the reaction system separately from vinyl acetate, and these Any of the methods of adding these may be used. When other monomers are added and introduced into the reaction system separately from the vinyl acetate, all other monomers are added to the reaction system all at once and introduced continuously, intermittently, etc. Any of the addition methods such as a method of adding and introducing them in combination or a method of combining them may be used.

  The amount of the other monomer used can be selected within a wide range depending on the desired properties of the emulsion. The amount used is, for example, 100 parts by mass or less (for example, 0.05 to 100 parts by mass, preferably 0.05 to 60 parts by mass, more preferably 0.05 to 40 parts by mass with respect to 100 parts by mass of vinyl acetate. )

  The monomer component such as vinyl acetate may be mixed with a protective colloid aqueous solution such as polyvinyl alcohol and added to the system in an emulsified state.

  The polymerization temperature in seed polymerization is, for example, about 60 to 90 ° C. (preferably 70 to 85 ° C.), but is not limited thereto.

  In the present invention, when another monomer (polymerizable unsaturated monomer other than vinyl acetate) is used as a monomer component, at least partially, in a form that is added to the system independently from vinyl acetate. The other monomer may be added to the reaction system in advance during the seed polymerization of vinyl acetate, or may be added to the reaction system before and after the seed polymerization of vinyl acetate. In addition, other monomers may be added to the reaction system before or after adding vinyl acetate to the system when seed polymerization of vinyl acetate. As described above, in the present invention, vinyl acetate (or mixed monomer) is added to the system and seed polymerization is performed (sometimes referred to as “PVac seed polymerization process”), and other monomers are vinyl acetate. If the step of adding it separately into the system (sometimes referred to as “another monomer addition step”) is provided, the low-temperature adhesive strength of the emulsion can be greatly improved.

  The PVac seed polymerization step includes the aforementioned step (A) and step (B). As the PVac seed polymerization step, acetic acid is used in the E-PVac emulsion so that the ratio (X) is 5% by mass or more and less than 25% by mass under the conditions satisfying the condition (a) or (b). There is no particular limitation as long as it is a step of introducing vinyl into the reaction system and performing seed polymerization. For example, as described above, (1) up to 25% of the time required to introduce all the vinyl acetate into the reaction system, the conditions satisfying the condition (a) or (b) are satisfied. Then, seed polymerization is performed while adding a predetermined amount of vinyl acetate (or mixed monomer) to the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass. After 25% of the time required for introduction into the reaction system has elapsed, the remaining portion of vinyl acetate (or mixed monomer) is added to the reaction system and seed polymerization is performed. And (2) up to 25% of the time required to introduce all the vinyl acetate into the reaction system, under the conditions satisfying the above condition (a) or (b), Ratio (X) is 5 mass% or more and less than 25 mass% Thus, a predetermined amount of vinyl acetate (or mixed monomer) is added all at once to the reaction system, and then seed polymerization is performed. Thereafter, the time required to introduce all the vinyl acetate into the reaction system is 25%. %, The remaining vinyl acetate (or mixed monomer) may be added to the reaction system for seed polymerization, and (3) all the vinyl acetate is reacted in the reaction system. The ratio (X) is not less than 5% by mass and less than 25% by mass up to 25% of the time required for introduction into the composition under the conditions satisfying the condition (a) or (b). After adding a part of a predetermined amount of vinyl acetate (or mixed monomer) to the reaction system, seed polymerization is performed while adding the remaining vinyl acetate (or mixed monomer) to the reaction system, Then all the vinyl acetate After 25% of the time required for introduction into the reaction system has elapsed, the remaining vinyl acetate (or mixed monomer) is added to the reaction system, and any process such as seed polymerization is performed. It may be a form process. Of course, after 25% of the time required to introduce all the vinyl acetate into the reaction system has elapsed, the remaining vinyl acetate (or mixed monomer) is added all at once to the reaction system, Polymerization may be performed.

  Therefore, the other monomer addition step is a step performed before adding vinyl acetate (or a mixed monomer) into the system in the PVac seed polymerization step (previous step of the PVac seed polymerization step). In the PVac seed polymerization step, vinyl acetate is added. (Or a mixed monomer) is added to the system (step after the PVac seed polymerization step), or a step performed during the PVac seed polymerization step (step performed during the PVac seed polymerization step). May be. As described above, it is advantageous to provide another monomer addition process as a pre-process of the PVac seed polymerization process or a post-process of the PVac seed polymerization process, or to provide another monomer addition process during the PVac seed polymerization process. An effect is obtained.

  As described above, another monomer addition step is performed as a pre-step of the PVac seed polymerization step. As described above, before adding vinyl acetate (or a mixed monomer) and performing seed polymerization, another monomer is added to the reaction system. Means to introduce. In this case, addition of another monomer can be performed in any state in the presence or absence of a polymerization initiator. That is, the polymerization of other monomers may be started before the start of polymerization of vinyl acetate, or may be started simultaneously with the start of the polymerization of vinyl acetate. In addition, after the polymerization of the other monomer is completed, a polymer by the other monomer (in the case where only one other monomer is used, a homopolymer, in the case where two or more other monomers are used, After their copolymers) are formed], a two-stage polymerization may be performed which proceeds to a PVac seed polymerization process.

  Further, performing the other monomer addition process as a subsequent process of the PVac seed polymerization process means that, as described above, after the addition of vinyl acetate (or mixed monomer) is completed, another monomer is added to the reaction system and introduced. , Meaning that the other monomer is subjected to polymerization. In this case, the addition of another monomer may be performed after the polymerization of vinyl acetate is completed.

  Furthermore, when the other monomer addition step is performed during the PVac seed polymerization step, as described above, during the seed polymerization by adding vinyl acetate (or mixed monomer), the other monomer is vinyl acetate. Means to be introduced separately into the reaction system and subjected to polymerization. In this case, the other monomer may be added at any stage during the PVac seed polymerization process (vinyl acetate addition stage, vinyl acetate addition and seed polymerization stage, vinyl acetate seed polymerization stage, etc.). Is preferably the first half of the PVac seed polymerization process (ie, the vinyl acetate addition stage).

  Thus, when adding other monomers into the system separately from vinyl acetate, the addition method of the other monomers may be any addition method of a batch addition method, a continuous addition method, and an intermittent addition method. However, as long as the reaction can be controlled, it is preferable to add in the shortest possible time as in the batch addition method. The temperature at which the other monomer is added to the system separately from the vinyl acetate is the same as the temperature (polymerization temperature) in the PVac seed polymerization step, but the other monomer addition step is the same as that in the PVac seed polymerization step. In the case where it is provided as a previous step and the polymerization of another monomer is started at the time of the PVac seed polymerization step, the temperature at the time of addition of the other monomer is not particularly limited. The other monomer may be mixed with a protective colloid aqueous solution such as polyvinyl alcohol and added to the system in an emulsified state.

  When other monomers are added to the system separately from the vinyl acetate, the amount of the other monomers added separately can be appropriately selected within a range that does not impair the performance such as adhesion of the emulsion. It is the range of about 0.05-10 mass parts with respect to 100 mass parts of vinyl acetate. If the amount used is less than 0.05 parts by mass, the adhesive strength during low-temperature curing (low-temperature adhesive strength) tends to decrease, and if it exceeds 10 parts by mass, the normal adhesive strength tends to decrease. Among the ranges described above, the range in which the adhesive strength is excellent and the decrease in the low-temperature adhesive strength during low-temperature curing is the smallest is 0.1 to 7 parts by mass (particularly preferably 0.5 to 100 parts by mass of vinyl acetate). -4 mass parts).

  In the present invention, the monomer component to be subjected to seed polymerization is often a monomer having a composition (kind) different from that of the monomer constituting the seed polymer, or a monomer having the same composition but different composition ratio. .

  In seed polymerization, a protective colloid may be used. The protective colloid may be pre-mixed in the E-PVac emulsion used for seed polymerization of monomer components such as vinyl acetate and mixed monomers, and may be used for seed polymerization of monomer components such as vinyl acetate and mixed monomers. In addition, it may be used by being mixed in a monomer component (such as vinyl acetate or a mixed monomer) added to the E-PVac emulsion. The protective colloid used in the seed polymerization is not particularly limited, and a protective colloid generally used in producing a vinyl acetate resin emulsion, for example, polyvinyl alcohol (PVA), other water-soluble polymers, and the like is preferable. used. The polyvinyl alcohol may be, for example, modified polyvinyl alcohol such as acetoacetylated polyvinyl alcohol, in addition to general polyvinyl alcohol. The polyvinyl alcohol may be either a partially saponified product or a completely saponified product, and two or more kinds of polyvinyl alcohols having different molecular weights or saponification degrees may be used in combination. Thus, when polyvinyl alcohol as a protective colloid is present in the reaction system of the seed polymerization, the polyvinyl alcohol has an effective function as an emulsifier in the seed polymerization, and the coating workability when used as an adhesive is improved. improves.

  The amount of the protective colloid can be appropriately selected within a range that does not impair the polymerizability at the time of seed polymerization or the adhesiveness when used as an adhesive, but generally the total resin (total solid content) of the resulting vinyl acetate resin emulsion ) Is, for example, about 2 to 40% by mass (preferably 5 to 30% by mass, more preferably 8 to 25% by mass).

  The polymerization initiator (polymerization catalyst) used in seed polymerization is not particularly limited, and is a known or commonly used polymerization initiator such as an organic peroxide such as hydrogen peroxide or benzoyl peroxide, ammonium persulfate, peroxide. Potassium sulfate, sodium persulfate, azobisisobutyronitrile and the like can be used. These polymerization initiators may be used as a redox polymerization initiator in combination with a reducing agent such as tartaric acid, sodium bisulfite, and ascorbic acid. The amount of the polymerization initiator used is, for example, 0.05 to 2 parts by mass with respect to 100 parts by mass of the total amount of monomers to be subjected to seed polymerization (total amount of vinyl acetate and other monomers used as necessary). Degree. Moreover, the usage-amount of the reducing agent at the time of using a redox type polymerization initiator can be suitably set according to the kind etc. of the said polymerization initiator. As a chain transfer agent, isopropanol, dodecyl mercaptan, etc. may be added in a small amount in the system.

  In the seed polymerization, other additives (for example, a surfactant, a pH adjuster, etc.) may be added as long as the polymerizability and the performance as an adhesive are not impaired. As a polymerization method, a known polymerization method can be used, and examples thereof include, but are not limited to, a monomer sequential addition method, a batch charging method, and a two-stage polymerization method. The polymerization apparatus is not particularly limited, and an atmospheric emulsion polymerization apparatus used in the industry can be used.

The PVac emulsion of the present invention is a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, as described above. The ratio (X) of vinyl acetate introduced to the total amount of vinyl acetate introduced by 25% of the time required for introduction into the reaction system, and the gel fraction of the ethylene-vinyl acetate copolymer resin emulsion ( Y) is introduced into the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass under the following conditions (a) or (b). It is prepared by seed polymerization of vinyl acetate. Therefore, the PVac emulsion of the present invention can exhibit excellent low-temperature film-forming properties and high adhesive strength even in the state containing no plasticizer, and particularly excellent low-temperature adhesive strength even during low-temperature curing. Can be prevented, and a significant decrease in adhesive strength during low-temperature curing can be prevented. For example, the retention value represented by the following formula can usually be 60% or higher, and can reach 70% or higher, or 80% or higher depending on the manufacturing conditions.
Retention rate (%) = [low temperature (5 ° C.) adhesive strength (N / mm ² ) / normal adhesive strength (N / mm ² )] × 100

  In addition, the said normal state adhesive strength shows the adhesive strength when an emulsion is used as an adhesive for woodworking, and is the value of the compression shear adhesive strength measured based on JIS K 6852. The low temperature (5 ° C.) adhesive strength is the adhesive strength when the emulsion is used as an adhesive for woodworking. The emulsion and the test piece are stored in an atmosphere at 5 ° C. for 1 day, and then at the same temperature. It is the value of the compressive shear bond strength measured according to JIS K 6852, except that it is bonded, cured and measured at the same temperature.

The normal adhesion strength of the PVac emulsion of the present invention is, for example, 10 N / mm ² or more (for example, 10 to 30 N / mm ² ), preferably 15 N / mm ² or more (for example, 15 to 30 N / mm ² ).

  In addition, when the PVac emulsion of the present invention is applied to an adherend, a transparent film can be formed even when it is formed on various substrates at a low temperature as described above.

  The PVac emulsion of the present invention can be used as an aqueous adhesive as it is, but if necessary, a water-soluble polymer such as a cellulose derivative can be blended as a thickener, or a filler, solvent, pigment, dye , Antiseptics, antifoaming agents, precipitation inhibitors, fluidity improvers, rust inhibitors, wetting agents, and the like may be added.

  The aqueous adhesive of the present invention is an aqueous adhesive comprising the PVac emulsion, and in a preferred embodiment of the aqueous adhesive, it does not substantially contain a plasticizer (volatile plasticizer). The phrase “substantially free of a plasticizer” means that, for example, a pigment paste to be added contains a plasticizer, which does not prevent the plasticizer from being mixed into the adhesive. In addition, the total amount of the resin contained in the aqueous adhesive is, for example, about 20 to 80% by mass (preferably 30 to 65% by mass) with respect to the total amount of the aqueous adhesive as a solid content (non-volatile content). In particular, it is preferably 35 to 50% by mass (in particular, 40 to 45% by mass). Such a solid content ratio can be appropriately selected according to the type of the water-based adhesive, the conditions for applying the water-based adhesive (for example, temperature conditions), and the like.

  The PVac emulsion of the present invention is a so-called “non-VOC-type water-based adhesive” that can be used as an adhesive that can be reassured not only for the industry but also for school children and medical use. The PVac emulsion of the present invention can be used for various purposes such as a paint base and a coating agent in addition to an adhesive. When the PVac emulsion of the present invention is used as various processing agents such as paint bases and coating agents, the ratio of the solid content is the type of the processing agent and the conditions for applying the processing agent (for example, temperature conditions). Etc.) etc., for example, can be selected from the same range as in the case of an aqueous adhesive.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by these Examples.

Example 1
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer, 500 parts by mass of water is added, and under stirring, the product name “Kuraray Poval 224” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)] ]: 45 parts by mass, trade name “Kuraray Poval 117” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)]: 10 parts by mass and tartaric acid: 1 part by mass were dissolved and kept at 80 ° C. After PVA (trade name “Kuraray Poval 224” and trade name “Kuraray Poval 117”) is completely dissolved, an ethylene-vinyl acetate copolymer resin emulsion (trade name “Sumikaflex S-467HQ” manufactured by Sumitomo Chemical Co., Ltd.) Solid content: 65% by mass, gel fraction: 45% by mass) was added in an amount of 150 parts by mass. When the liquid temperature rose to 80 ° C., the catalyst [35% by mass hydrogen peroxide solution: an aqueous solution in which 1 part by mass was dissolved in 20 parts by mass of water] and vinyl acetate monomer: 180 parts by mass were separately added dropwise. It dripped continuously over 2 hours from the tank. The vinyl acetate monomer is 5% by mass of the total amount of vinyl acetate monomer (that is, 30 minutes after the start of dripping of vinyl acetate for 30 minutes). , 9 parts by mass), and 95% by mass of the total amount of vinyl acetate monomer (ie, 30 minutes after starting the reaction (30 minutes after starting the reaction) to 2 hours later) 171 parts by mass) was continuously added dropwise. After completion of the dropwise addition, the mixture was further stirred for 1.5 hours to complete the polymerization. Then, it cooled to room temperature and obtained the vinyl acetate resin-type emulsion. The solid content of this vinyl acetate resin emulsion was 35% by mass.

(Example 2)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-400HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 58 mass%) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 1.

(Example 3)
150 parts by mass of the trade name “Sumikaflex S-455HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 90 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 1.

(Comparative Example 1)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-510HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55% by mass, gel fraction: 1% by mass) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 1.

(Comparative Example 2)
Other than using 150 parts by mass of the trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo; solid content: 55 mass%, gel fraction: 17 mass%) as the ethylene-vinyl acetate copolymer resin emulsion Obtained a vinyl acetate resin emulsion (solid content: 35% by mass) in the same manner as in Example 1.

(Comparative Example 3)
Other than using 150 parts by mass of the trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo; solid content: 55 mass%, gel fraction: 30 mass%) as the ethylene-vinyl acetate copolymer resin emulsion Obtained a vinyl acetate resin emulsion (solid content: 35% by mass) in the same manner as in Example 1.

Example 4
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer, 500 parts by mass of water is added, and under stirring, the product name “Kuraray Poval 224” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)] ]: 45 parts by mass, trade name “Kuraray Poval 117” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)]: 10 parts by mass and tartaric acid: 1 part by mass were dissolved and kept at 80 ° C. After PVA (trade name “Kuraray Poval 224” and trade name “Kuraray Poval 117”) is completely dissolved, an ethylene-vinyl acetate copolymer resin emulsion (trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo Co., Ltd.) 150 parts by mass of solid content: 55% by mass, gel fraction: 17% by mass) When the liquid temperature rose to 80 ° C., the catalyst [35% by mass hydrogen peroxide solution: 1 part by mass water: 20 Aqueous solution dissolved in parts by mass] and 180 parts by mass of vinyl acetate monomer were continuously added dropwise over 2 hours from separate dropping tanks, 30 minutes after starting the reaction of vinyl acetate monomer. 10% by mass of the total amount of vinyl acetate monomer (that is, 18 masses) in the next 30 minutes (that is, 30 minutes after the beginning of dripping of vinyl acetate) Part) was continuously added dropwise, and 90% by mass (ie 162% by mass) of the total amount of vinyl acetate monomer in 90 minutes from 30 minutes after the start of the reaction (30 minutes after starting the reaction) to 2 hours later. After the completion of dropping, the mixture was further stirred for 1.5 hours to complete the polymerization, and then cooled to room temperature to obtain a vinyl acetate resin emulsion. The solid content of the system emulsion was 35% by mass.

(Example 5)
Other than using 150 parts by mass of the trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo; solid content: 55 mass%, gel fraction: 30 mass%) as the ethylene-vinyl acetate copolymer resin emulsion Obtained a vinyl acetate resin emulsion (solid content: 35% by mass) in the same manner as in Example 4.

(Example 6)
150 parts by weight of the trade name “Sumikaflex S-467HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 65 mass%, gel fraction: 45 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. A vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as Example 4 except for the above.

(Example 7)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-400HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 58 mass%) was used. A vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as Example 4 except for the above.

(Example 8)
150 parts by mass of the trade name “Sumikaflex S-455HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 90 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. A vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as Example 4 except for the above.

(Comparative Example 4)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-510HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55% by mass, gel fraction: 1% by mass) was used. A vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as Example 4 except for the above.

Example 9
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer, 500 parts by mass of water is added, and under stirring, the product name “Kuraray Poval 224” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)] ]: 45 parts by mass, trade name “Kuraray Poval 117” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)]: 10 parts by mass and tartaric acid: 1 part by mass were dissolved and kept at 80 ° C. After PVA (trade name “Kuraray Poval 224” and trade name “Kuraray Poval 117”) is completely dissolved, an ethylene-vinyl acetate copolymer resin emulsion (trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo Co., Ltd.) 150 parts by mass of solid content: 55% by mass, gel fraction: 17% by mass) When the liquid temperature rose to 80 ° C., the catalyst [35% by mass hydrogen peroxide solution: 1 part by mass water: 20 Aqueous solution dissolved in parts by mass] and 180 parts by mass of vinyl acetate monomer were continuously added dropwise over 2 hours from separate dropping tanks, 30 minutes after starting the reaction of vinyl acetate monomer. 15% by weight of the total amount of vinyl acetate monomer (that is, 27 mass) in the subsequent 30 minutes (that is, 30 minutes after the beginning of dripping of vinyl acetate) Part) was continuously added dropwise, and 85% by mass of the total amount of vinyl acetate monomer (that is, 153% by mass) in 90 minutes from 30 minutes after the start of the reaction (30 minutes after starting the reaction) to 2 hours later. After the completion of dropping, the mixture was further stirred for 1.5 hours to complete the polymerization, and then cooled to room temperature to obtain a vinyl acetate resin emulsion. The solid content of the system emulsion was 35% by mass.

(Example 10)
Other than using 150 parts by mass of the trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo; solid content: 55 mass%, gel fraction: 30 mass%) as the ethylene-vinyl acetate copolymer resin emulsion Obtained a vinyl acetate resin emulsion (solid content: 35% by mass) in the same manner as in Example 9.

(Example 11)
150 parts by weight of the trade name “Sumikaflex S-467HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 65 mass%, gel fraction: 45 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 9.

(Example 12)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-400HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 58 mass%) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 9.

(Example 13)
150 parts by mass of the trade name “Sumikaflex S-455HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 90 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 9.

(Comparative Example 5)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-510HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55% by mass, gel fraction: 1% by mass) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 9.

(Example 14)
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank and a thermometer, 500 parts by mass of water is added, and under stirring, the product name “Kuraray Poval 224” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)] ]: 45 parts by mass, trade name “Kuraray Poval 117” [manufactured by Kuraray Co., Ltd., polyvinyl alcohol (PVA)]: 10 parts by mass and tartaric acid: 1 part by mass were dissolved and kept at 80 ° C. After PVA (trade name “Kuraray Poval 224” and trade name “Kuraray Poval 117”) is completely dissolved, an ethylene-vinyl acetate copolymer resin emulsion (trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo Co., Ltd.) 150 parts by mass of solid content: 55% by mass, gel fraction: 17% by mass) When the liquid temperature rose to 80 ° C., the catalyst [35% by mass hydrogen peroxide solution: 1 part by mass water: 20 Aqueous solution dissolved in parts by mass] and 180 parts by mass of vinyl acetate monomer were continuously added dropwise over 2 hours from separate dropping tanks, 30 minutes after starting the reaction of vinyl acetate monomer. 20% by mass of the total amount of vinyl acetate monomer (that is, 36 mass) in the next 30 minutes (that is, 30 minutes after the beginning of dripping of vinyl acetate) Part) was continuously added dropwise, and 80% by mass (ie, 144% by mass) of the total amount of vinyl acetate monomer in 90 minutes from 30 minutes after the start of the reaction (30 minutes after starting the reaction) to 2 hours later. After the completion of dropping, the mixture was further stirred for 1.5 hours to complete the polymerization, and then cooled to room temperature to obtain a vinyl acetate resin emulsion. The solid content of the system emulsion was 35% by mass.

(Example 15)
Other than using 150 parts by mass of the trade name “Denka Supertex NS300” (manufactured by Denki Kagaku Kogyo; solid content: 55 mass%, gel fraction: 30 mass%) as the ethylene-vinyl acetate copolymer resin emulsion Obtained a vinyl acetate resin emulsion (solid content: 35% by mass) in the same manner as in Example 14.

(Example 16)
150 parts by weight of the trade name “Sumikaflex S-467HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 65 mass%, gel fraction: 45 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 14.

(Example 17)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-400HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 58 mass%) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 14.

(Example 18)
150 parts by mass of the trade name “Sumikaflex S-455HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55 mass%, gel fraction: 90 mass%) was used as the ethylene-vinyl acetate copolymer resin emulsion. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 14.

(Comparative Example 6)
As an ethylene-vinyl acetate copolymer resin emulsion, 150 parts by mass of “Sumikaflex S-510HQ” (manufactured by Sumitomo Chemical Co., Ltd .; solid content: 55% by mass, gel fraction: 1% by mass) was used. Except for the above, a vinyl acetate resin emulsion (solid content: 35% by mass) was obtained in the same manner as in Example 14.

(Method for measuring gel fraction of ethylene-vinyl acetate copolymer resin emulsion)
About each ethylene-vinyl acetate copolymer resin-type emulsion used by each Example and each comparative example, the gel fraction (mass%) was calculated | required as follows.
An ethylene-vinyl acetate copolymer resin emulsion was applied on a fluororesin plate in a coating amount so that the thickness (film thickness) after drying was 200 μm, and then dried at room temperature (20 to 25 ° C.). A film of an ethylene-vinyl acetate copolymer resin emulsion was obtained. After finely cutting the film, the finely cut form of the film in an atmosphere of 50 ° C. in 100 times the amount of toluene with respect to the mass of the film (the mass of the film is “W ¹ ”) to thereby immersed, for 5 hours, then filtered through a 200-mesh metal gauze. The filtration residue on the wire mesh was washed with toluene and dried to obtain a toluene-insoluble part insoluble in toluene (the mass of the toluene-insoluble part is “W ² ”). And the gel fraction (mass%) of ethylene-vinyl acetate copolymer resin-type emulsion was calculated | required by following Formula.
Gel fraction (mass%) = (W ² / W ¹ ) × 100

(Evaluation)
Each vinyl acetate resin emulsion obtained in each Example and each Comparative Example was evaluated for storage stability, minimum film-forming temperature according to JIS standards, and low-temperature film-forming property for porous materials by the following methods. The evaluation results are shown in Tables 1 to 4. In Tables 1 to 4, “EVA gel fraction (mass%)” is the gel fraction (mass%) of the ethylene-vinyl acetate copolymer resin emulsion used in each example and each comparative example. In addition, the “drop ratio (mass%) of Vac in the initial stage of the reaction” is the ratio of vinyl acetate monomer dropped in 30 minutes from the start of the reaction to 30 minutes later (relative to the total amount of vinyl acetate monomer). Ratio) (mass%).

(Storage stability evaluation method)
For each vinyl acetate resin emulsion obtained in each Example and each Comparative Example, using a BH viscometer, the rotor no. 5 was used, and the viscosity (Pa · s) was measured under the condition of the rotational speed: 10 r / min. This viscosity is defined as “initial viscosity”.

  In addition, each vinyl acetate resin emulsion obtained in each Example and each Comparative Example was allowed to stand for 30 days in an incubator (model “SOFT INCUBATOR SL1-10000ND” manufactured by EYELA) set at 50 ° C. Then, it was taken out and left in a water bath at a temperature of 23 ° C. for 3 hours. Thereafter, using a BH viscometer, the rotor No. 5 was used, and the viscosity (Pa · s) was measured under the condition of the rotational speed: 10 r / min. The viscosity is defined as “viscosity after 30 ° C. × 30 days”.

Furthermore, the viscosity increase ratio when allowed to stand at 50 ° C. for 30 days was determined from the following equation using the initial viscosity measured for each vinyl acetate resin emulsion and the viscosity after 30 ° C. × 30 days. The viscosity increase ratio is “50 ° C. × 30 days after viscosity increase”. Viscosity increase = 50 ° C. × viscosity after 30 days / initial viscosity

(Measurement method of minimum film-forming temperature according to JIS standards)
In accordance with JIS K 6804 (7.6 Minimum film-forming temperature) using a film-formation tester (equipment product name “MFT test equipment” manufactured by Riken Seiki Seisakusho; model number “LT”). Measured. Therefore, in this measurement, a metal material (non-porous material) is used as a base material (substrate) to be applied when forming a film.

(Evaluation method of low-temperature film-forming properties for porous materials)
A thermo-hygrostat (model “LHU-112T” manufactured by Tabai Espec Co., Ltd.) was set at 0 ° C., and samples (vinyl acetate resin emulsions obtained in each example and each comparative example), plywood (thickness) 3 mm; type 1), glass rods were stored for 7 days. It was 2 degreeC when the temperature of each sample was measured using the alcohol thermometer. Moreover, it was 2 degreeC when the surface temperature of the plywood was measured using the surface thermometer (model "SK-1250MC" by Sato Meter Co., Ltd.). In an atmosphere of 2 ° C. and 60% RH, each sample is uniformly applied to the surface of the plywood having a surface temperature of 2 ° C. using a glass rod (2 ° C.) with a coating amount of 300 μm after drying. It was applied and allowed to stand in the same atmosphere for 1 day to form a film. The film was visually checked for transparency, and the low-temperature film-forming property for the porous material was evaluated for each sample according to the following criteria.
(Double-circle): A dry film is beautifully transparent on the whole surface.
○: The dry film is partially translucent.
Δ: The dry film is translucent over the entire surface.
X: The dry film is entirely white and opaque.

  As is clear from Tables 1 to 4, even when the vinyl acetate resin emulsion according to the example is left at 50 ° C. for 30 days, the rate of increase in viscosity is small and the storage stability is good. Further, the minimum film-forming temperature according to JIS standard (JIS K 6804) is 0 ° C. or less, and in that case, a transparent film is formed, and the low-temperature film-forming property for non-porous materials is excellent. Yes. Furthermore, even when the plywood is formed at a low temperature, a transparent film can be formed.

  In particular, such vinyl acetate resin-based emulsions are produced under mild conditions in which the amount of vinyl acetate monomer introduced in the initial stage of polymerization is small.

  Of course, the vinyl acetate resin emulsion according to the example does not substantially contain a plasticizer and hardly contains a VOC component.

Claims (5)

A method for producing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, which is 25 times the time required to introduce all the vinyl acetate into the reaction system. % (X) of vinyl acetate introduced by the time of% to the total amount of vinyl acetate introduced and the gel fraction (Y) of the ethylene-vinyl acetate copolymer resin emulsion are the following conditions (a) or (b ), Vinyl acetate is introduced into the reaction system so that the ratio (X) is 5% by mass or more and less than 25% by mass, and vinyl acetate is seed-polymerized. the method of manufacturing resin emulsion [However, the gel fraction (Y) is an ethylene - vinyl acetate copolymer resin emulsion, on a fluorine-based resin plate, the thickness after drying (thickness) of 200μ After coating with a coating amount to be dried at room temperature (20 to 25 ° C.) to obtain a film with an ethylene-vinyl acetate copolymer resin emulsion, this film was cut into small pieces in an atmosphere of 50 ° C. , Soaked in 100 times the amount of toluene with respect to the mass of the film (referred to as “W ¹ ”), treated for 5 hours, and then filtered through a 200-mesh wire mesh. It was washed and dried to obtain a toluene-insoluble matter (mass is “W ² ”), which was obtained by the following formula.
Gel fraction (mass%) = (W ² / W ¹ ) × 100].
(A): When the ratio (X) is 5% by mass or more and less than 10% by mass, the gel fraction (Y) is 40% by mass or more. (B): The ratio (X) is 10% by mass or more and 25 When it is less than mass%, the gel fraction (Y) is 15 mass% or more. The vinyl acetate is removed from the reaction system by any one of the following methods (i) to (iii) within a time period up to 25% of the time required to introduce all the vinyl acetate into the reaction system. The method for producing a vinyl acetate resin-based emulsion according to claim 1, which is introduced into the method.
(I): A predetermined amount of vinyl acetate is introduced into the reaction system dropwise while seed polymerization is performed. (Ii): A predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization. ): A part of vinyl acetate in a predetermined amount of vinyl acetate is introduced into the reaction system in advance before starting the seed polymerization, and the remaining vinyl acetate is introduced into the reaction system by dropwise addition while performing seed polymerization. Do   The method for producing a vinyl acetate resin emulsion according to claim 1 or 2, wherein the ratio (X) is 10% by mass or more and 20% by mass or less.   The vinyl acetate resin emulsion according to any one of claims 1 to 3, which is a vinyl acetate resin emulsion obtained by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion. A vinyl acetate resin emulsion prepared by the method.   An aqueous adhesive comprising a vinyl acetate resin emulsion, wherein the vinyl acetate resin emulsion is the vinyl acetate resin emulsion according to claim 4.