JP2000239307A - Production of vinyl acetate resin-based emulsion and aqueous adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vinyl acetate resin-based emulsion having excellent low temperature film formability and strength of adhesive bonding even in the case of not containing any plasticizer at all, and having high bonding strength even in low temperature curing. SOLUTION: This method for producing a vinyl acetate resin-based emulsion is to perform the seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin-based emulsion to produce the vinyl acetate resin-based emulsion and to comprise the following processes: (1) the seed polymerization of vinyl acetate while adding it into the above reaction system; (2) the addition of a polymerizable unsaturated monomer other than vinyl acetate into the above reaction system independently of the addition of vinyl acetate during performing the process 1. The quantity consumed of the polymerizable unsaturated monomer is e.g. about 0.05-10 pts.wt. based 100 pts.wt. vinyl acetate. The polymerizable unsaturated monomer other than vinyl acetate can be e.g. at least one kind selected from the group consisting of acrylates, methacrylates and vinyl esters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl acetate resin emulsion and an aqueous adhesive comprising the vinyl acetate resin emulsion. The vinyl acetate resin emulsion is useful as an adhesive, a paint base, a coating agent, and the like. The aqueous adhesive is suitable as a plasticizer-free aqueous adhesive.

[0002]

2. Description of the Related Art Conventionally, vinyl acetate resin emulsions have been widely used for adhesives and paints for woodworking, paper processing, fiber processing and the like. However, since the minimum film-forming temperature is high as it is, it is often necessary to add a film-forming auxiliary such as a volatile plasticizer or an organic solvent. Phthalate esters and the like are used as the plasticizer.However, due to the recent increase in environmental problems, it has been pointed out that phthalate esters are not preferable for the environment, and alternatives to highly safe plasticizers and the like have been made. Is being considered. However, the plasticizer is essentially a VOC component (Volatile Organic Compo
unds; volatile organic compounds), and there is a view that the VOC component may be a causative agent of new-building disease (sick house syndrome), particularly in an adhesive used for housing. As described above, even with a water-based adhesive having a small environmental load, the VOC problem caused by the plasticizer has been pointed out. Therefore, a vinyl acetate resin-based emulsion adhesive containing no plasticizer is being studied, but there is no technology that exhibits high adhesive strength enough to be used for woodworking and that can form a film at low temperatures such as in winter. .

In the specification of Japanese Patent Application No. 9-270358, the present applicant discloses that the ethylene content is 15 to 35% by weight.
A woodworking adhesive containing a vinyl acetate resin emulsion obtained by seed-polymerizing vinyl acetate with an ethylene-vinyl acetate copolymer resin emulsion is proposed. According to this technique, high adhesive strength is exhibited, and an unprecedented excellent performance that a film can be formed even at a low temperature such as in winter without adding a plasticizer can be obtained. However, when only vinyl acetate is used as a monomer to be used for seed polymerization, there is a problem that the low-temperature adhesive strength during low-temperature curing such as winter is small. In winter or cold regions, if the desired adhesive strength cannot be obtained even under daily conditions such as bonding to an adherend and curing at a low temperature, the reliability of the adhesive is greatly lost.

[0004] Thus, at present, there is no technology for obtaining a non-plastic water-based adhesive which is excellent in film-forming properties at low temperatures and can perform bonding work reliably at low temperatures, and there is no technology that can solve this socially. It is expected.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide excellent low-temperature film-forming properties and adhesive strength even without containing a plasticizer at all, and high adhesive strength (low-temperature curing) even during low-temperature curing. It is an object of the present invention to provide a method for producing a vinyl acetate resin emulsion having an adhesive strength, and an aqueous adhesive comprising the vinyl acetate resin emulsion having the excellent performance.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted various studies on polymerization, processing, and modification techniques of a vinyl acetate resin-based emulsion, and have obtained the following findings. I got That is, in producing a vinyl acetate resin emulsion by seed polymerization of vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, seed polymerization is performed while adding vinyl acetate to the ethylene-vinyl acetate copolymer resin emulsion. When butyl acrylate (BA) is added to the system independently of the vinyl acetate during the process, the adhesive strength during low-temperature curing that is observed when only vinyl acetate is subjected to seed polymerization is greatly reduced. That the phenomenon disappears.
Similar effects were obtained when butyl methacrylate (BMA) was used instead of butyl acrylate.

On the other hand, when the seed polymerization was carried out while adding a mixed solution of vinyl acetate and BA or BMA to the reaction system, the above-mentioned effect was not obtained at all. In these results, instead of adding vinyl acetate and BA etc. in the form of a mixture in the system, during the step of performing seed polymerization while adding vinyl acetate into the system, butyl acrylate etc. It is a first mystery that the above-mentioned effects are exhibited when they are added and blended into the system independently of the above. It is a second mystery that similar effects can be obtained with BA, which is a soft monomer capable of forming a film at a low temperature when formed into a polymer, and BMA, which is a hard monomer which is difficult to form a film at a low temperature when formed into a polymer. is there.

After obtaining the above findings, the present inventors have studied in more detail the types and amounts of the polymerizable unsaturated monomers to be added to the system, and have completed the present invention.

That is, the present invention relates to a method for producing a vinyl acetate resin emulsion by seed-polymerizing vinyl acetate in an ethylene-vinyl acetate copolymer resin emulsion, wherein the vinyl acetate is added to the emulsion while adding vinyl acetate to the system. A method for producing a vinyl acetate resin-based emulsion, comprising a step of performing polymerization and a step of adding a polymerizable unsaturated monomer other than vinyl acetate to the system independently of the vinyl acetate during the step. .

According to this production method, when the obtained emulsion is used as an adhesive, excellent low-temperature film-forming properties, adhesive properties, adhesive strength, and adhesive workability can be obtained without containing any plasticizer. In addition to this, it is possible to prevent the conventional problem that the low-temperature adhesive strength during the low-temperature curing is significantly reduced.

In the above method, the amount of the polymerizable unsaturated monomer other than vinyl acetate may be in the range of 0.05 to 10 parts by weight based on 100 parts by weight of vinyl acetate. When the amount of the polymerizable unsaturated monomer other than vinyl acetate is set in the above range, particularly excellent low-temperature film formability, adhesiveness, and adhesive strength are prevented while preventing a significant decrease in low-temperature adhesive strength during low-temperature curing. And adhesion workability can be obtained.

In the above-mentioned production method, at least one monomer selected from acrylates, methacrylates and vinyl esters is used as the polymerizable unsaturated monomer other than vinyl acetate. Is also good. When such a monomer is used, a decrease in low-temperature adhesive strength during the low-temperature curing can be suppressed to a minimum.

The present invention also provides an aqueous adhesive comprising a vinyl acetate resin-based emulsion obtained by the above-mentioned production method. This water-based adhesive is excellent in low-temperature film formability, adhesiveness, adhesive strength and adhesive workability even without containing a plasticizer at all, and significantly reduces the low-temperature adhesive strength during low-temperature curing, which is a conventional problem. It is a new concept adhesive that can be stopped. Preferred aqueous adhesives are substantially free of plasticizers (volatile plasticizers) such as phthalates.

In the present specification, “seed polymerization” is used in a broad sense in which monomers are polymerized in a resin emulsion. Further, “acryl” and “methacryl” may be collectively referred to as “(meth) acryl”.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an ethylene-vinyl acetate copolymer resin emulsion is used as a seed emulsion. The ethylene-vinyl acetate copolymer resin constituting this emulsion is not particularly limited, but usually a copolymer resin having an ethylene content of about 5 to 40% by weight is used. Among them, ethylene content is 15-35
The copolymer resin in the range of weight% is particularly preferable because it gives a particularly low film-forming temperature and also has excellent adhesive strength. Ethylene-vinyl acetate copolymer resin emulsions are widely marketed and can be easily found in the market. The ethylene-vinyl acetate copolymer-based emulsion is used after being diluted with water as necessary.

The amount of the ethylene-vinyl acetate copolymer resin is
The content of the obtained vinyl acetate resin emulsion in the total resin (total solid content) is, for example, about 3 to 40% by weight, preferably about 5 to 30% by weight, and more preferably about 10 to 25% by weight.

The seed polymerization is carried out in the above-mentioned ethylene-vinyl acetate copolymer resin emulsion and preferably in an aqueous emulsion containing polyvinyl alcohol (PVA) as a protective colloid in the presence of a polymerization initiator.

When polyvinyl alcohol is present in the polymerization system, the polyvinyl alcohol has an effective function as an emulsifier in seed polymerization, and also improves coating workability and adhesive strength when used as an adhesive.

The polyvinyl alcohol is not particularly limited, and polyvinyl alcohol generally used for producing a vinyl acetate resin emulsion or an ethylene-vinyl acetate copolymer resin emulsion can be used. Polyvinyl alcohol may be used. 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 and degrees of saponification may be used in combination.

The amount of polyvinyl alcohol 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. The total solid content) is, for example, 2 to 40% by weight, preferably 5 to 3% by weight.
It is about 0% by weight, more preferably about 8 to 25% by weight.

In the system, protective colloids other than polyvinyl alcohol and surfactants (nonionic surfactants, anionic surfactants, cationic surfactants) are contained within a range that does not impair the polymerizability or the function as an adhesive. Activator, etc.).

The polymerization initiator is not particularly limited, and may be a conventional initiator such as hydrogen peroxide, an organic peroxide such as benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, or azobisisobutyrate. Ronitrile and the like can be used. These initiators can also be used as redox initiators in combination with reducing agents such as tartaric acid, Rongalit, sodium bisulfite, ascorbic acid and the like. The amount of the polymerization initiator used is, for example, about 0.05 to 2 parts by weight based on 100 parts by weight of the total amount of the monomers (vinyl acetate and a polymerizable unsaturated monomer other than vinyl acetate). The amount of the reducing agent used when using the redox initiator can be appropriately set according to the type of the initiator and the like. In addition, as a chain transfer agent, isopropanol,
A small amount of an organic solvent such as dodecyl mercaptan may be added to the system.

The main feature of the production method of the present invention is that a step of performing seed polymerization while adding vinyl acetate to the system (hereinafter, referred to as a step).
(Hereinafter sometimes simply referred to as “Step A”), and polymerizable unsaturated monomers other than vinyl acetate (hereinafter sometimes simply referred to as “other monomers”) during the above step are independent of the vinyl acetate. (Hereinafter simply referred to as “Step B”)
In some cases).

The method for adding vinyl acetate in the step A may be either continuous addition or intermittent addition.
Vinyl acetate may be mixed with an aqueous solution of protective colloid such as polyvinyl alcohol, emulsified, and added to the system. In the present invention, during the step of performing seed polymerization while adding vinyl acetate into the system, the step of adding a polymerizable unsaturated monomer other than vinyl acetate into the system independently of the vinyl acetate. As long as it does not impair the addition of the polymerizable unsaturated monomer other than vinyl acetate to the vinyl acetate in the system, as long as the reactivity and the adhesive performance of the obtained emulsion are not impaired. Absent. The amount of vinyl acetate used for seed polymerization is, for example, 10 to 90 with respect to the total resin (total solid content) of the obtained vinyl acetate resin-based emulsion.
% By weight, preferably about 15 to 80% by weight, and more preferably about 40 to 75% by weight. The polymerization temperature in step A is, for example, about 60 to 90 ° C, preferably about 70 to 85 ° C.

The polymerizable unsaturated monomer other than vinyl acetate used in the step B is not particularly restricted but includes, for example, acrylic esters, methacrylic esters, vinyl esters, aromatic vinyl compounds, and unsaturated vinyl compounds. Examples include saturated carboxylic acid amides, olefins, dienes, unsaturated nitriles, and the like. These polymerizable unsaturated monomers can be used alone or in combination of two or more.

As the acrylates and methacrylates, any of the conventionally known (meth) acrylates can be used. Typical examples thereof are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meth) acrylate alkyl esters such as octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; hydroxyethyl (meth) acrylate, (meth) acryl Hydroxyalkyl (meth) acrylate such as hydroxypropyl acrylate, methoxymethyl (meth) acrylate, alkoxyalkyl (meth) acrylate such as ethoxymethyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid And polyoxyethylene glycol, polyoxyp Esters of polyoxyalkylene glycols such as propylene glycol (acryloyl compound having a polyoxyalkylene structure, or methacryloyl compound)
(Meth) acrylic acid esters containing a reactive functional group such as

As the vinyl esters, any of conventionally known vinyl esters other than vinyl acetate can be used. Typical examples thereof include, for example, vinyl formate; vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate,
Vinyl stearate, vinyl octylate, VEOBA 10
(Trade name: manufactured by Shell Japan Co., Ltd.); vinyl esters of C _3-18 aliphatic carboxylic acids; and vinyl aromatic carboxylate such as vinyl benzoate.

Examples of the aromatic vinyl compound include styrene, vinyltoluene, α-methylstyrene, N-vinylpyrrolidone, vinylpyridine and the like. Unsaturated carboxylic amides include (meth) acrylamide, N
-(Meth) acrylamides such as methylolacrylamide, N-methoxymethylacrylamide, and N-methoxybutylacrylamide. Examples of the olefin include ethylene, propylene, butylene, isobutylene, pentene, and the like. Examples of dienes include butadiene, isoprene, chloroprene, and the like. Examples of the unsaturated nitriles include (meth) acrylonitrile.

Among these polymerizable unsaturated monomers, it is preferable to use at least one selected from acrylates, methacrylates and vinyl esters. Among them, (meth) acrylic acid alkyl esters [eg, (meth) acrylic acid C _1-18 alkyl esters, particularly (meth) acrylic acid C _1-14 alkyl esters], and C _3-14 aliphatic carboxylic acid vinyl esters are _preferred. This is preferable since the decrease in low-temperature adhesive strength during low-temperature curing is minimized. In addition to the low-temperature adhesive strength, from the viewpoint of maintaining excellent low-temperature film forming performance and transparency of the formed film, more preferably, C _3-12 alkyl acrylate and C _2-8 alkyl methacrylate are preferred. And so on.

The amount of the other monomer can be appropriately selected within a range that does not impair the performance such as the adhesiveness of the emulsion. In general, the amount is 0.1 to 100 parts by weight of vinyl acetate.
It is in the range of about 05 to 10 parts by weight. The amount used is 0.
If it is less than 05 parts by weight, the adhesive strength during low-temperature curing (low-temperature adhesive strength) tends to decrease, and if it exceeds 10 parts by weight, the normal-state adhesive strength tends to decrease. Among the above ranges, the range in which the adhesive strength is excellent and the decrease in the low-temperature adhesive strength during the low-temperature curing is the least is 0.1 to 100 parts by weight of vinyl acetate.
To 7 parts by weight, particularly preferably 0.5 to 4 parts by weight.

To add a polymerizable unsaturated monomer other than vinyl acetate into the system independently of vinyl acetate during step A:
During the seed polymerization by adding vinyl acetate to the system, it means that the other monomer is not mixed with vinyl acetate, but added separately from vinyl acetate.

In the present invention, as compared with the case where seed polymerization is carried out while adding a mixture of vinyl acetate and another monomer, which is a normal copolymer form, to the system, the other monomer in the system is used. It is considered that the polymerization of the other monomer proceeds in a state where the proportion of the other monomer is large.

The method of adding the other monomer in step B may be any of batch addition, continuous addition, and intermittent addition. The time for adding the other monomer is shorter than the time for adding vinyl acetate. It is preferable that the other monomer is added as short as possible, as in a batch addition method, as long as the reaction can be controlled. Further, the other monomer may be added to the system after mixing and emulsifying with an aqueous solution of protective colloid such as polyvinyl alcohol. The temperature in the step B is the same as the temperature in the step A. The timing of adding the other monomer may be at any stage during the process A, but is preferably in the first half of the process A.

The polymerization apparatus is not particularly limited, and a normal pressure emulsion polymerization apparatus that is commonly used in the industry can be used.

The vinyl acetate resin emulsion obtained by the method of the present invention has excellent low-temperature film-forming properties (for example, when the minimum film-forming temperature is 0 ° C.) even when no plasticizer is contained.
), High adhesive strength as well as high adhesive strength as well as preventing a significant decrease in adhesive strength during low-temperature curing.

The vinyl acetate resin emulsion obtained by the method of the present invention also has a feature that when applied to an adherend, a transparent film is formed.

In the present invention, the reason why the adhesive strength at the time of low-temperature curing is high as described above is not necessarily clear, but as described above, in the method of the present invention, the total amount of the other monomers in the system is reduced. Since the polymerization of the other monomer proceeds in a state where the ratio of the other monomer to the body is relatively large, a homopolymer of the other monomer (a copolymer thereof when two or more of the other monomers are used) or This is considered to be due to a high generation ratio of the block copolymer of the other monomer and vinyl acetate and a low generation ratio of the random copolymer of the other monomer and vinyl acetate. However, if the above-mentioned effects can be seen only when acrylates having a lower glass transition point of the homopolymer than the vinyl acetate homopolymer are used, the homopolymer of the other monomer is generally used. It can be guessed that it functions as a film-forming aid in the film formation process at low temperatures like a simple plasticizer, but it is a case where a monomer with a relatively high glass transition point of a homopolymer such as butyl methacrylate is used. Can not explain that it is effective. Therefore, the formation of a complex core-shell structure under the special condition of seed polymerization using an ethylene-vinyl acetate copolymer resin as a seed produces special effects such as uniform temperature dependency during film formation. It is presumed to be some element.

The vinyl acetate resin emulsion obtained by the method of the present invention can be used as it is as an aqueous adhesive. However, if necessary, a water-soluble polymer such as a cellulose derivative may be blended as a thickener. Alternatively, a filler, a solvent, a pigment, a dye, a preservative, an antifoaming agent and the like may be added. In a preferred embodiment of the aqueous adhesive of the present invention, a plasticizer (volatile plasticizer) is substantially not contained. The term "substantially free of a plasticizer" means that, for example, a plasticizer is contained in a pigment paste or the like to be added, and therefore does not prevent mixing of the plasticizer into the adhesive.

The aqueous adhesive thus obtained has a high adhesive strength and does not decrease its adhesive strength even at the time of low-temperature curing. Therefore, it is suitable as an aqueous adhesive for woodworking, paperwork and the like, particularly for woodworking. . The total amount of the resin contained in the water-based adhesive is, for example, about 25 to 70% by weight, preferably about 30 to 60% by weight, as a solid content.

If the residual monomers contained in the vinyl acetate resin-based emulsion obtained by the method of the present invention are completely removed by a conventionally known technique, a so-called “non-VO” can be obtained.
"C-type water-based adhesive", which is an extremely safe adhesive not only for industry but also for school children and medical use. Further, the vinyl acetate resin emulsion obtained by the method of the present invention can be used for various purposes such as a paint base and a coating agent as well as an adhesive.

[0041]

According to the production method of the present invention, excellent low-temperature film formability and adhesive strength can be obtained without containing a plasticizer at all, and the adhesive strength (low-temperature adhesive strength) even when cured at low temperature. A vinyl acetate resin-based emulsion which does not decrease in water content can be obtained. Further, the aqueous adhesive of the present invention exhibits excellent low-temperature film formability and adhesive strength even without containing any plasticizer, and has high adhesive strength even during low-temperature curing.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, the physical property test of the vinyl acetate resin-based emulsion obtained in each example was performed by the following method.

(Minimum film forming temperature) Using a film forming tester, JI
It was measured in accordance with SK 6804 (7.6 minimum film formation temperature). (Viscosity) The viscosity was measured using a BH type viscometer at 23 ° C. and 10 rpm.

(Normal Adhesion Strength) The compression shear adhesion strength when the obtained emulsion was used as a woodworking adhesive was measured. The test was performed based on JIS K 6852, and a combination of birch wood and birch wood was used as a test piece to be used. The state of breakage of the adherend was examined, and the ratio of the broken area to the shear area was defined as the material breakage rate (%).

(Low-temperature adhesive strength) Except that the emulsion and the test piece were cooled in a 5 ° C atmosphere while being held for one day, then bonded and cured in a 5 ° C atmosphere, and measured in a 5 ° C atmosphere. Was measured in the same manner as the above-mentioned normal adhesive strength.
The state of breakage of the adherend was examined, and the ratio of the broken area to the shear area was defined as the material breakage rate (%).

(Retention) The value determined by the following equation was defined as the retention. Retention rate (%) = [low-temperature adhesive strength (kgf / cm ² ) / normal adhesive strength (kgf / cm ² )] × 100 (transparency of film)
Under an atmosphere of 0% RH, it was applied to a thickness of 100 μm on a glass plate and cured for one day to form a film. The transparency of this film was visually evaluated according to the following criteria. ：: almost transparent Δ: turbidity observed ×: completely opaque

Example 1 505 parts by weight of water was placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, and polyvinyl alcohol (PVA) (Kuraray Co., Ltd., Kuraray Poval PVA) was added thereto.
224) 55 parts by weight of tartaric acid and 0.7 parts by weight of tartaric acid were added and dissolved, and kept at 80 ° C. After the PVA was completely dissolved, 125 ethylene-vinyl acetate copolymer resin emulsion (EVA emulsion) (manufactured by Denki Kagaku Kogyo KK, Denka Supertex NS100, solid content concentration 55% by weight) was added to 125
Parts by weight were added. When the liquid temperature rises to 80 ° C,
To this mixture, a catalyst (an aqueous solution in which 1 part by weight of 35% by weight hydrogen peroxide solution was dissolved in 22 parts by weight of water) and 285 parts by weight of a vinyl acetate monomer were placed in separate dripping tanks at a constant speed for 2 hours. And continuously dropped. Then, when 1/4 of the total amount of the vinyl acetate monomer was dropped, 6 parts by weight of n-butyl acrylate (BA) was added to the system at once from another dropping tank. After the completion of the dropwise addition of the catalyst and the vinyl acetate monomer, the mixture was further stirred for 1.5 hours to complete the polymerization, thereby obtaining a vinyl acetate resin emulsion.

Example 2 When 1/2 of the total amount of the vinyl acetate monomer was dropped,
The same operation as in Example 1 was performed except that 6 parts by weight of n-butyl acrylate (BA) was added to the system at a time, to obtain a vinyl acetate resin-based emulsion.

Example 3 When 3/4 of the total amount of the vinyl acetate monomer was dropped,
The same operation as in Example 1 was performed except that 6 parts by weight of n-butyl acrylate (BA) was added to the system at a time, to obtain a vinyl acetate resin-based emulsion.

Example 4 As an added monomer, n-methacrylic acid was used in place of BA.
A vinyl acetate resin-based emulsion was obtained in the same manner as in Example 1 except that 9 parts by weight of butyl (BMA) was used.

Example 5 A vinyl acetate resin emulsion was obtained in the same manner as in Example 1, except that 12 parts by weight of vinyl laurate (VL) was used instead of BA as an added monomer.

Comparative Example 1 A vinyl acetate resin emulsion was obtained in the same manner as in Example 1 except that BA was not added.

Comparative Example 2 505 parts by weight of water was placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, and 55 parts by weight of PVA (Kuraray Co., Ltd., Kuraray Poval PVA224) and tartaric acid 0 were added. Then, 0.7 parts by weight were added and dissolved, and kept at 80 ° C. P
After the VA was completely dissolved, EVA emulsion (manufactured by Denki Kagaku Kogyo KK, Denka Supertex NS100,
125 parts by weight of a solid content concentration of 55% by weight) were added. When the liquid temperature rose to 80 ° C., a catalyst (a solution of 1 part by weight of 35% by weight hydrogen peroxide dissolved in 22 parts by weight of water), 285 parts by weight of vinyl acetate monomer and 6 parts by weight of BA Was continuously dropped at a constant speed from separate dropping tanks over 2 hours. After the completion of the dropwise addition, the mixture was further stirred for 1.5 hours to complete the polymerization to obtain a vinyl acetate resin emulsion.

Reference Example 1 A commercially available vinyl acetate resin-based emulsion containing 10% by weight of dibutyl phthalate (plasticizer) with respect to the total resin (homo vinyl acetate resin-based emulsion manufactured by Konishi Co., Ltd.) was used as Reference Example 1. .

The physical properties of the vinyl acetate resin emulsions obtained in the above Examples, Comparative Examples and Reference Examples are shown in Table 1. In the table, the retention is a value obtained by the above-mentioned formula.

[0056]

[Table 1] As is evident from Table 1, the vinyl acetate resin-based emulsions of the Examples did not contain a plasticizer, but were compared with commercially available plasticizer-containing vinyl acetate resin-based emulsions (Reference Example 1). In addition to the low minimum film formation temperature, the performance was comparable to that of the adhesive strength. On the other hand, in the vinyl acetate resin emulsion of the comparative example, the lowest film formation temperature shows a low value as in the example, but the low-temperature adhesive strength and the retention are significantly inferior to those of the vinyl acetate resin emulsion of the example. Was.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shintaro Ogawa 4-7-9 Tsurumi, Tsurumi-ku, Osaka-shi, Osaka F-term in Konishi Corporation Osaka Research Laboratory (reference) 4J011 AA05 BB01 BB09 KA16 KB14 KB19 PA64 PC02 PC06 4J040 DE041 JA02 JA12 LA06 MB08 4J100 AA02Q AA03Q AA06Q AA07Q AB02Q AB03Q AB04Q AG02Q AG03Q AG04P AL03Q AL04Q AL05Q AL08Q AL09Q AL10Q AM02Q AM15Q AM21Q AQ08Q AQ12Q AS02Q AS03Q AS07Q BA03Q BA05FA03 FA03 FA03 FA03

Claims (6)

[Claims] 1. A method for producing a vinyl acetate resin-based emulsion by seed-polymerizing vinyl acetate in an ethylene-vinyl acetate copolymer-based resin emulsion, wherein the step of performing seed polymerization while adding vinyl acetate into the system. And a step of adding a polymerizable unsaturated monomer other than vinyl acetate to the system during the step independently of the vinyl acetate. 2. The amount of the polymerizable unsaturated monomer other than vinyl acetate is 0.05 to 100 parts by weight of vinyl acetate.
The method for producing a vinyl acetate resin-based emulsion according to claim 1, wherein the amount is 10 parts by weight. 3. The polymerizable unsaturated monomer other than vinyl acetate is at least one monomer selected from acrylates, methacrylates and vinyl esters. A method for producing a vinyl acetate resin emulsion. 4. An aqueous adhesive comprising a vinyl acetate resin emulsion obtained by the production method according to claim 1. 5. The aqueous adhesive according to claim 4, substantially free of a plasticizer. 6. The aqueous adhesive according to claim 4, which is used for woodworking.