JP2003082310A - adhesive - Google Patents

Abstract

(57) [Problem] To provide an ethylene-vinyl acetate-based resin emulsion-based adhesive which has less environmental problems, has less coloring, and is excellent in initial adhesive strength. SOLUTION: A vinyl alcohol-based polymer having a degree of saponification of 70 mol% or more is used as a dispersant, and the amount of unreacted vinyl acetate monomer contained in the emulsion is 0.2% by weight or less and the formaldehyde concentration is 1 ppm or less. An adhesive mainly composed of a vinyl acetate resin emulsion.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a small amount of unreacted residual vinyl acetate monomer contained in an emulsion,
In addition, the present invention relates to an adhesive containing an ethylene-vinyl acetate-based resin emulsion containing little or no formaldehyde as a main component.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as P
VA) may be used as a protective colloid for ethylene-vinyl acetate resin emulsion,
It has been widely used as an adhesive for plastics such as plywood / vinyl chloride. However, it has been recently pointed out that vinyl acetate monomers have mutagenicity, and it is strongly desired to reduce unreacted vinyl acetate monomers remaining in a small amount in emulsions used for adhesives in consideration of the environment. However, since the ethylene-vinyl acetate resin emulsion is a copolymer with ethylene, it is difficult to reduce the amount of unreacted vinyl acetate monomer.
The present situation is that it contains about 5% by weight of unreacted vinyl acetate monomer. On the other hand, in the conventional polymerization of ethylene-vinyl acetate resin emulsion, hydrogen peroxide is widely used from the viewpoint of polymerization stability, water resistance of the emulsion, etc., and the redox reaction with hydrogen peroxide is sensitive. , Sodium formaldehyde sulfoxylate (commonly known as Rongalit, hereinafter referred to as Rongalit) is often used. However, Rongalit has a serious problem that formaldehyde is contained in the obtained emulsion because it produces formaldehyde upon decomposition.
Due to recent environmental problems, the use of Rongalit has been avoided. Under these circumstances, in order to reduce the amount of unreacted vinyl acetate monomer, it is essential to reconstruct the polymerization initiator and the polymerization conditions. JP 2001-16
In Japanese Patent No. 3910, it is reported that erythorbic acid and ascorbic acid can be converted into non-formaldehyde by using as a reducing agent, but it is difficult to reduce unreacted vinyl acetate monomer in the initiator system, and hydrogen peroxide is also used. There is a problem that coloring occurs in the obtained emulsion unless a large amount of is used, and it is not yet sufficient.

[0003]

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and provides an adhesive containing an ethylene-vinyl acetate resin emulsion as a main component, which causes less environmental problems. The first purpose is
Further, in addition to these properties, a second object is to provide an adhesive containing an ethylene-vinyl acetate resin emulsion as a main component, which is less colored and is excellent in initial adhesive strength.

[0004]

The first object of the present invention is to provide an emulsion containing 0.2% by weight or less of unreacted vinyl acetate monomer and 1% formaldehyde concentration.
This is accomplished by providing an adhesive based on an ethylene-vinyl acetate resin emulsion that is below ppm. The second object of the present invention is ethylene-
Vinyl acetate resin emulsion has a saponification degree of 70 mol%
When the above vinyl alcohol polymer is used as a dispersant and a redox polymerization initiator composed of hydrogen peroxide, tartaric acid and / or its metal salt is used to emulsion-polymerize ethylene and vinyl acetate, the pH of the polymerization system is adjusted to 3 To 7 and the emulsion was polymerized by adding an iron compound, and when the amount of unreacted vinyl acetate monomer in the polymerization system became 5% by weight or less,
Ethylene obtained by adding hydroperoxides
This is accomplished by providing the above adhesive which is a vinyl acetate resin emulsion.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION When preparing an ethylene-vinyl acetate resin emulsion which is the main component of the adhesive of the present invention,
The vinyl alcohol-based polymer having a saponification degree of 70 mol% or more (hereinafter sometimes abbreviated as PVA-based polymer) used as a dispersant is obtained by saponifying a vinyl ester-based polymer by a conventional method. You can

The dispersant may be a copolymer of ethylenically unsaturated monomers copolymerizable within the range not impairing the object of the present invention. Examples of such ethylenically unsaturated monomers include ethylene, propylene, acrylic acid, methacrylic acid, fumaric acid, (anhydrous) maleic acid, itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and trimethyl- (3-
Acrylamide-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinylpyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, fluorine Examples thereof include vinylidene chloride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate, and the like. Further, a terminal modified product obtained by polymerizing vinyl acetate in the presence of a thiol compound such as thiolacetic acid and mercaptopropionic acid and saponifying it can also be used. Among these ethylenically unsaturated monomers, ethylene is preferable, and the content of ethylenically unsaturated monomers, especially ethylene is 0.5 to 2
It is preferably 0 mol%, more preferably 1 to 15 mol%.

The saponification degree of the PVA polymer is 70 mol%.
It is necessary that the content is not less than 80 mol%, more preferably not less than 80 mol%, further preferably not less than 85 mol%. If the degree of saponification is less than 70 mol%, the water solubility, which is the original property of the PVA polymer, decreases, and sufficient adhesiveness may not be obtained. Further, in order to more suitably achieve the object of the present invention, the viscosity average degree of polymerization of the PVA polymer is preferably in the range of 100 to 8000, and 300 to 3
000 is more preferable.

The amount of the PVA polymer used as the dispersant is not particularly limited, but in order to more preferably achieve the object of the present invention, 100 parts by weight of dispersoid (ethylene-vinyl acetate resin). On the other hand, the amount is preferably 2 to 15 parts by weight, more preferably 3 to 10 parts by weight.

In the present invention, ethylene and vinyl acetate are mainly used as monomers during emulsion polymerization. However, ethylenically unsaturated monomers and / or diene-based monomers are used as long as the object of the present invention is not impaired. The body may be copolymerized. Examples of such a monomer include propylene, olefins such as isobutylene, vinyl chloride, vinyl fluoride, vinylidene chloride, halogenated olefins such as vinylidene fluoride, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, Acrylic acid and its esters such as 2-ethylhexyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, methacrylic acid Methacrylic acid and its esters such as 2-hydroxyethyl acid, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and their quaternary products, as well as acrylamide and methacrylic acid. Bromide, N- methylolacrylamide, N, N- dimethylacrylamide, acrylamide-based monomers such as acrylamido-2-methylpropanesulfonic acid and its sodium salt, styrene, alpha
-Styrene-based monomers such as methylstyrene, p-styrenesulfonic acid and sodium and potassium salts, and other N
Examples thereof include vinylpyrrolidone and the like, diene-based monomers such as butadiene, isoprene and chloroprene, and polyfunctional monomers such as triallyl cyanurate, triallyl isocyanurate and diallyl phthalate.

The content of ethylene in the dispersoid obtained by emulsion polymerization is not particularly limited, but is preferably 5 to 50% by weight, and more preferably 10 to 40% by weight. When the ethylene content is in this range, the adhesiveness,
In particular, the adhesion of paper, wood, and plastics (such as vinyl chloride film) to substrates is improved.

When the ethylene-vinyl acetate resin emulsion used in the present invention is produced, a redox type polymerization initiator composed of hydrogen peroxide and tartaric acid and / or its metal salt is used as a polymerization initiator. L-dextrorotatory as tartaric acid
There are (+) tartaric acid, levorotatory D (-) tartaric acid, DL tartaric acid which is a racemic compound of these enantiomers, and there is no particular limitation, but when L (+) tartaric acid is used among these,
Little coloring, good initial adhesion, and good emulsion polymerization controllability. It is also possible to use a metal salt of tartaric acid, and the kind of metal is not particularly limited, but sodium tartarate is usually used. Above all, L
(+) Sodium tartrate is preferably used. L
When (+) sodium tartrate is used, in addition to the above advantages, there is an advantage that pH adjustment with an alkali such as ammonia or caustic soda that is usually performed after emulsion polymerization is not necessary. The amount of hydrogen peroxide used is preferably 0.01 to 0.2 part by weight, and more preferably 0.02 to 0.15 part by weight, based on 100 parts by weight of all the monomers. .

The ratio of hydrogen peroxide to tartaric acid and / or its metal salt is not particularly limited, but usually 50 to 300 parts by weight of tartaric acid and / or its metal salt, preferably 100 parts by weight of hydrogen peroxide. 70 to 250 parts by weight, more preferably 80 to 200 parts by weight are used.
By using tartaric acid and / or its metal salt in this range, there is little coloring and good initial adhesion,
Also, the controllability of polymerization is improved. The redox-based polymerization initiator usually indicates the amount used until the unreacted vinyl acetate monomer reaches 5% by weight.

In the present invention, the pH of the emulsion polymerization system is 3 to 7,
It is preferably adjusted to 4 to 6. By adjusting the pH within this range, coloring is reduced, initial adhesiveness is improved, and polymerization controllability is also improved. The method for adjusting the pH of the emulsion polymerization system is not particularly limited, and any buffering agent can be used, but sodium acetate, acetic acid / sodium acetate system, sodium hydroxide, sodium carbonate and the like are usually preferably used. In the present invention, the pH of the emulsion polymerization system refers to the pH from the beginning of the polymerization to the end of the polymerization, and in the present invention, the pH at any point in the polymerization system.
Is preferably 3 to 7.

In the present invention, it is preferable to add an iron compound to the emulsion polymerization system. The iron compound is not particularly limited, but at least one iron compound selected from ferrous chloride, ferrous sulfate, ferric chloride, ferric nitrate, and ferric sulfate is preferably used, among which ferric chloride is used. Ferrous iron and ferrous sulfate are particularly preferably used.

The amount of iron compound used is not particularly limited,
The amount used is 1 ppm to 100 ppm, more preferably 5 ppm to 50 ppm, based on all monomers. By using the iron compound in this range, the coloring is reduced, the initial adhesiveness is good, and the polymerization controllability is also good.

The method for adding the redox polymerization initiator is not particularly limited. Examples of the method of performing hydrogen peroxide by ordinary emulsion polymerization, that is, a method of adding in a shot at the initial stage of polymerization initiation, a method of sequentially adding during hydrogenation, and the like can be mentioned. The tartaric acid and / or its metal salt may be used by adding the entire amount at the initial stage of the emulsion polymerization, or may be added sequentially during the emulsion polymerization, but the total amount is usually added at the initial stage of the emulsion polymerization and used. . The addition method of the iron compound is not particularly limited, but it is usually used by adding the entire amount at the initial stage of emulsion polymerization.

In the present invention, it is preferable to add hydroperoxides when the amount of unreacted vinyl acetate monomer in the polymerization system becomes 5% by weight or less. Preferably, the hydroperoxides are added at the time when the amount becomes 4% by weight or less. By adding hydroperoxides at this point, coloring is reduced, initial adhesion is improved, and polymerization controllability is also improved. Examples of hydroperoxides include t-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, and 1,1,3,3-tetramethylbutylhydroperoxide. Among them, t-butyl hydroperoxide and cumene hydroperoxide are preferably used.

The amount of hydroperoxides to be added is not particularly limited, but is usually 0.
005 to 5 molar equivalents, preferably 0.01 to 3 molar equivalents are added. When the added amount is less than 0.005 molar equivalent,
The unreacted vinyl acetate monomer may exceed 0.2% by weight. If the amount added exceeds 5 molar equivalents, the water resistance of the resulting adhesive may decrease.

In the present invention, when the hydroperoxides are added, tartaric acid and / or a metal salt thereof is added, particularly, at the same time, the unreacted vinyl acetate monomer can be efficiently reduced. The addition amount of tartaric acid and / or its metal salt used here is not particularly limited, but usually, relative to 1 mol of hydroperoxides,
0.1 to 3 mol is used. If the addition amount is less than 0.1 mol, the effect of adding tartaric acid and / or its metal salt may not be seen, and even if the amount exceeds 3 mol, the effect may not be expected.

The emulsion polymerization of the present invention is carried out under pressure, preferably 2
It is carried out under a pressure of 0 to 70 kg / cm ² , but during the emulsion polymerization, for example, when the residual vinyl acetate concentration becomes 10% by weight, it is 5 to 35 kg / cm from the initial polymerization pressure.
^{2 At a} low pressure, preferably 10 to 30 kg / cm ² low pressure, a part of ethylene is released, and when the residual vinyl acetate concentration becomes 5% by weight or less, hydroperoxides are added. It is preferred to complete the polymerization.

In the present invention, 30 to 200 m after emulsion polymerization
1 under reduced pressure of mHg, preferably 50 to 180 mmHg.
0 to 70 ° C, preferably 15 to 60 ° C, 0.5 to
By performing ethylene removal for 5 hours, preferably 1 to 4 hours, the amount of unreacted vinyl acetate monomer can be reduced more reliably.

The adhesive obtained by the present invention has an unreacted vinyl acetate monomer content of 0.2 in the emulsion.
It is essential that the content of the formaldehyde is 1% by weight or less and the concentration of formaldehyde is 1 ppm or less. Here, the measurement of the amount of unreacted vinyl acetate monomer in the emulsion refers to the value measured by the titration method described in JIS K6828. When the amount of unreacted vinyl acetate monomer exceeds 0.2% by weight, it cannot be said that the amount of unreacted vinyl acetate monomer has been reduced, and the object of the present invention cannot be achieved. Further, the measurement of the formaldehyde concentration is a value measured using a gas detector tube. When the concentration of formaldehyde contained in the emulsion is 1 ppm or more, a so-called non-formaldehyde emulsion cannot be obtained and the object of the present invention cannot be achieved.

As the adhesive obtained by the production method of the present invention, the ethylene-vinyl acetate resin emulsion obtained by the above-mentioned method can be used as it is. However, if necessary, the effect of the present invention is not impaired. Various conventionally known emulsions can be added and used. As the dispersant used in the present invention, a PVA polymer having a saponification degree of 70 mol% or more is used. If necessary, a conventionally known anionic, nonionic or cationic surfactant or , PVA-based polymer, hydroxyethyl cellulose and the like can be used together.

The adhesive obtained by the production method of the present invention has a small amount of unreacted vinyl acetate monomer in the adhesive,
It has the characteristics of containing little or no formaldehyde, has less coloring, and has excellent initial adhesive strength. Therefore, paper tube, bag making, interleaving paper, paper for corrugated board, adhesive for paper such as pulp, adhesive for woodworking such as general woodworking and adhesive for plastics such as plywood / vinyl chloride, and water-based urethane resin, etc. It is widely and suitably used as an adhesive for plastics containing the above.

[0025]

The present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, "part" and "%" mean weight basis unless otherwise specified. In addition, the physical properties of the emulsion such as the amount of unreacted vinyl acetate monomer and the content of formaldehyde in the obtained adhesive, and the performance as an adhesive were evaluated in the following manner.

(Evaluation method) (1) Amount of unreacted vinyl acetate monomer It was measured by the vinyl acetate monomer quantification method described in JIS K6806. (2) Formaldehyde content 0.1ml of the adhesive was collected in a 10ml glass vial, and
After heating at 0 ° C for 1 hr, gas detector tube (No. 171SB:
Measured with Komei Rikagaku Kogyo, 100 ml suction). (3) Initial Adhesion At 20 ° C. and 65% relative humidity (RH), 100 g / m ^{2 of the} adhesive shown in the following Examples and Comparative Examples was applied to kraft paper with a bar coater, and immediately the same kind of adhesive was used. Kraft papers were stuck together, lightly pressed by a hand roller, and bonded. After that, 5 seconds, 10 seconds, 20 seconds, 30
After a second, the material was peeled off and the time at which the material was broken was determined. (4) A test body was prepared under the conditions below the amount of formaldehyde emission from the adherend and used for the test. [Adhesion conditions] Adhering material: Kraft paper / craft paper application amount: 100 g / m ² (double-sided application) Deposition time: 1 minute Pressing condition: 20 ° C., 1 hour, pressure 5 kg / cm ² After pressing, It was submitted to the test. A container containing 300 ml of distilled water is placed at the bottom of a desiccator 240 mm in size specified in JIS R3503 (Glassware for chemical analysis), and the laminated kraft paper cut out to a size of 2.5 cm × 7.5 cm (test 10 pieces of body) are fixed to the support metal fittings,
The sample was allowed to stand at 20 ° C. for 24 hours so that they would not come into contact with each other, and the formaldehyde released was absorbed in distilled water to prepare a sample solution. Using this sample solution, the amount of formaldehyde was measured by the acetylacetone method shown on page 19 of "Ordinary Plywood" edited by JAS Wood. (5) Colorability The above laminated kraft paper was exposed to 1 at 100 ° C in an air atmosphere.
After left for 0 minutes, the adhesive layer between the kraft papers was visually observed, and the coloring state was judged according to the following criteria. ○ No coloration △ Colored slightly yellow × Colored yellow

Example 1 1061 g of PVA-1 (polymerization degree: 1700, saponification degree: 88 mol%, PVA-217 manufactured by Kuraray Co., Ltd.) in an autoclave having a pressure resistance of 50 liter equipped with a nitrogen blowing port, a thermometer and a stirrer, and an ion Exchanged water 19440 g, L (+) tartaric acid 8.3 g, sodium acetate 10 g, ferrous chloride 0.4
g was charged and completely dissolved at 95 ° C., then cooled to 60 ° C. and replaced with nitrogen. Next, vinyl acetate 22360g
Then, ethylene was pressurized up to 45 kg / cm ² . Emulsion polymerization was carried out by pressurizing 1000 g of a 0.4% aqueous hydrogen peroxide solution over 5 hours. PH of polymerization system at the beginning of polymerization
Was 5.2. When the residual vinyl acetate concentration reached 10%, ethylene was released and the ethylene pressure was 20 kg /
The pressure was adjusted to cm ² and 50 g of a 3% aqueous hydrogen peroxide solution was press-fitted.
When the residual vinyl acetate concentration reached 3%, 1
% T-butyl hydroperoxide (t-BHPO) 21
Polymerization was completed by pressurizing 1 g. After cooling, the pH was confirmed to be pH = 4.1. The pH of the emulsion was adjusted to 5.5 by adding 230 g of a 10% aqueous sodium hydroxide solution, and the emulsion was filtered using a 60-mesh stainless steel wire net. As a result, an ethylene-vinyl acetate resin emulsion having a solid content concentration of 54.3% and an ethylene content of 18% by weight was obtained. The evaluation of this emulsion as an adhesive was performed by the method described above. The results are shown in Table 1.

Comparative Example 1 Except that sodium acetate was not used in Example 1,
Emulsion polymerization was tried in the same manner as in Example 1, but the progress of emulsion polymerization was extremely slow, and the polymerization could not be completed.

Example 2 Instead of 8.3 g of L (+) tartaric acid in Example 1,
Emulsion polymerization was carried out in the same manner as in Example 1 except that 12.7 g of L (+) sodium tartrate was used, and the solid content concentration was 54.
An ethylene-vinyl acetate resin emulsion having 4% and an ethylene content of 18% by weight was obtained. The obtained emulsion was evaluated as an adhesive in the same manner as in Example 1. The results are shown in Table 1.
Shown in.

Example 3 In Example 2, after t-BHPO was press-fitted, L was further added.
270 g (t-) of a 10% aqueous solution of (+) sodium tartrate.
An ethylene-vinyl acetate resin emulsion having a solid content concentration of 54.2% and an ethylene content of 18% by weight was obtained in the same manner as in Example 2 except that 1 mol of BHPO and 0.19 mol of sodium tartrate were injected under pressure. The emulsion thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 A pressure-resistant 50 liter autoclave equipped with a nitrogen blowing port, a thermometer and a stirrer was charged with 1061 g of PVA-1, ion-exchanged water of 19440 g and ferrous chloride of 0.4 g.
After completely dissolving at 5 ° C. and then cooling to 60 ° C., 8.2 g of Rongalit was added to perform nitrogen substitution. Next, after charging 22360 g of vinyl acetate, 45 k of ethylene was added.
Pressurized to g / cm ² . 0.4% hydrogen peroxide solution 1
000 g was injected under pressure for 5 hours to carry out emulsion polymerization. The pH of the polymerization system at the initial stage of the polymerization was 3.6. When the residual vinyl acetate concentration reached 10%, ethylene was released, the ethylene pressure was adjusted to 20 kg / cm ^2, and 50 g of a 3% aqueous hydrogen peroxide solution was injected. Furthermore, the residual vinyl acetate concentration is 3%
Then, 211 g of 1% t-BHPO was injected under pressure to complete the polymerization. After cooling, pH was confirmed to be pH = 2.8. The pH of the emulsion was adjusted to 5.5 by adding 230 g of a 10% aqueous sodium hydroxide solution, and the emulsion was filtered using a 60-mesh stainless steel wire net. As a result, the solid content concentration was 54.5% and the ethylene content was 1
An 8% by weight ethylene-vinyl acetate resin emulsion was obtained. The evaluation was performed by the method described above. The results are shown in Table 1.

Comparative Example 3 A pressure-resistant 50 liter autoclave equipped with a nitrogen blowing port, a thermometer and a stirrer was charged with 1061 g of PVA-1, ion-exchanged water of 19440 g and ferrous chloride of 0.4 g.
After completely dissolving at 5 ° C. and then cooling to 60 ° C., 9.4 g of L-ascorbic acid was added to perform nitrogen substitution. Next, after charging 22360 g of vinyl acetate, 4 ethylene was added.
The pressure was increased to 5 kg / cm ² . Emulsion polymerization was carried out by pressurizing 1000 g of a 0.4% aqueous hydrogen peroxide solution over 5 hours. The pH of the polymerization system at the initial stage of the polymerization was 3.9. When the residual vinyl acetate concentration reached 10%, ethylene was released, the ethylene pressure was adjusted to 20 kg / cm ^2, and 50 g of a 3% aqueous hydrogen peroxide solution was injected. Further, when the residual vinyl acetate concentration reached 3%, 211 g of 1% t-BHPO and 216 g of a 10% aqueous solution of L-ascorbic acid were press-fitted to complete the polymerization. After cooling, the pH was confirmed to be pH = 3.4. The pH of the emulsion was adjusted to 5.5 by adding 230 g of a 10% aqueous sodium hydroxide solution, and the emulsion was filtered using a 60-mesh stainless steel wire net. As a result, the solid content concentration was 54.2% and the ethylene content was 1
An 8% by weight ethylene-vinyl acetate resin emulsion was obtained. The evaluation was performed by the method described above. The results are shown in Table 1.

Comparative Example 4 Emulsion polymerization was tried in the same manner as in Example 1 except that ferrous chloride was not used, but the controllability of the polymerization was poor and it was dangerous, so it was stopped halfway.

Comparative Example 5 Emulsion polymerization was carried out in the same manner as in Example 1 except that t-BHPO was not used, and the solid content concentration was 54.5.
%, An ethylene-vinyl acetate resin emulsion having an ethylene content of 18% by weight was obtained. The emulsion thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Cumene hydroperoxide (cumene HPO) was used in place of t-BHPO used in Example 1, except that
Emulsion polymerization was carried out in the same manner as in Example 1 to obtain a solid content concentration of 5
An ethylene-vinyl acetate resin emulsion having 4.3% and an ethylene content of 18% by weight was obtained. The emulsion thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

The adhesive containing ethylene-vinyl acetate resin emulsion of the present invention as a main component has a small amount of unreacted vinyl acetate monomer contained in the emulsion and contains little or no formaldehyde. Low environmental problems, less coloring, and excellent initial adhesive strength. Therefore, paper tube, bag making, interleaving paper, paper for corrugated board, adhesive for paper such as pulp, adhesive for woodworking such as general woodworking and adhesive for plastics such as plywood / vinyl chloride, and water-based urethane resin, etc. It is widely and suitably used as an adhesive for plastics containing the above.

Continued front page    F term (reference) 4J040 DA051 DD022 DE031 JA03                       JB05 LA11 MA08 MA09 MA10                       QA01

Claims (5)

[Claims] 1. Ethylene having a vinyl alcohol polymer having a degree of saponification of 70 mol% or more as a dispersant, the amount of unreacted vinyl acetate monomer contained in the emulsion being 0.2% by weight or less, and the formaldehyde concentration being 1 ppm or less. An adhesive containing a vinyl acetate resin emulsion as a main component. 2. An ethylene-vinyl acetate resin emulsion comprising a vinyl alcohol polymer having a saponification degree of 70 mol% or more as a dispersant, and a redox polymerization initiator comprising hydrogen peroxide and tartaric acid and / or a metal salt thereof. make use of,
When emulsion-polymerizing ethylene and vinyl acetate, the pH of the polymerization system is adjusted to 3 to 7, an iron compound is added and emulsion-polymerized, and the amount of unreacted vinyl acetate monomer in the polymerization system is 5
The adhesive according to claim 1, which is an ethylene-vinyl acetate-based resin emulsion obtained by adding hydroperoxides when the content becomes less than or equal to wt%. 3. The adhesive according to claim 1, wherein the adhesive is a paper adhesive. 4. The adhesive is a woodworking adhesive.
Or the adhesive according to 2. 5. The adhesive according to claim 1, which is an adhesive for plastics.