JP2000072945A - Vinyl acetate resin emulsion and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin emulsion being excellent in stabilization during polymerization and having a low minimum film-forming temperature and therefore being capable of forming a film without being plasticized by dispersing microparticles of a copolymer comprising vinyl acetate (A) and a diacetoneacrylamide (B) in a specified ratio in water containing a polyvinyl alcohol(PVA) type polymer. SOLUTION: The comonomer ratio of component A to component B is 100:1 to 100:40 by weight. The PVA resin used as a dispersant is exemplified by an unmodified PVA or a modified PVA and is obtained by saponifying a polymer of a fatty acid vinyl ester or a copolymer of a fatty acid vinyl ester with a copolymerizable vinyl monomer. The fatty acid vinyl ester used is, for example, vinyl acetate. The vinyl monomer used is, for example, crotonic acid. It is desirable that the PVA resin has a viscosity of 3 Pa.s or above (in a 4% aqueous solution at 20 deg.C) and a degree of saponification of 85 mol% or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a vinyl acetate resin emulsion and a method for producing the same.
Further, the present invention relates to a vinyl acetate resin emulsion without using a plasticizer and a method for producing the same.

[0002]

2. Description of the Related Art A vinyl acetate resin emulsion is capable of controlling viscosity in a wide range by selecting a polyvinyl alcohol (hereinafter abbreviated as PVA) and a formulation to be used as a dispersant, and has a fluidity and fluidity. It is used for a wide range of applications including adhesives and paints because of its excellent stability such as mechanical stability and chemical stability, as well as its physical properties such as adhesiveness and glossiness of the film. ing.

However, the vinyl acetate resin emulsion itself has a high minimum film formation temperature (hereinafter abbreviated as MFT) and does not form a film when the temperature is low such as in winter, and exhibits excellent physical properties such as adhesiveness. do not do. Therefore, a plasticizer such as dibutyl phthalate is usually added to a vinyl acetate resin emulsion to reduce the MFT.

Although such a plasticizer has a high effect of lowering the MFT of a vinyl acetate resin emulsion (plasticizing effect), on the other hand, its toxicity has been a problem in recent years. It is a kind of environmental hormone and has a problem that its use is restricted due to its effects on the human body and the environment.

[0005]

In view of the above-mentioned problem of the toxicity of the plasticizer, an acrylic monomer having a bulky side chain such as n-butyl acrylate or 2-ethylhexyl acrylate is copolymerized with vinyl acetate. Accordingly, studies have been made to lower the MFT by internal plasticization of a polymer that is a main component of the emulsion.

However, when a PVA-based resin is used as a protective colloid when copolymerizing an acrylic monomer, poor polymerization occurs, aggregates are formed, and a satisfactory emulsion cannot be obtained. Further, when a surfactant is used instead of the PVA-based resin, polymerization proceeds stably, but only an emulsion having a very low viscosity is obtained, and there is a problem that mechanical and chemical stability are poor.

As means for solving these problems, JP-A-7-278212, JP-A-8-301908
Discloses a method of polymerizing an acrylic monomer using PVA having a mercapto group as a protective colloid, but in the presence of a compound used for producing PVA having a mercapto group, a polymer having a high molecular weight is used. However, emulsions obtained by applying these methods to vinyl acetate / acrylic emulsion polymerization have low viscosity, and emulsions have poor stability. It did not show satisfactory performance for emulsion applications.

In view of the above situation, the present invention provides a vinyl acetate resin emulsion which is excellent in various stability, has a low MFT, and can form a film without adding a plasticizer.
It is another object of the present invention to provide a method for producing a vinyl acetate resin emulsion in which a polymerization reaction proceeds stably.

[0009]

The present invention achieves the above object and has a copolymerization ratio expressed by weight of 10%.
A vinyl acetate-based resin emulsion in which fine particles of a copolymer of vinyl acetate and diacetone acrylamide (0: 1 to 100: 40) are dispersed in water containing a PVA-based polymer; A method for producing a vinyl acetate resin emulsion, comprising emulsion-polymerizing 100 parts by weight of a vinyl acetate monomer and 1 to 40 parts by weight of a diacetone acrylamide monomer in the presence of a dispersant comprising a coalesced water and water. It is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the vinyl acetate resin emulsion of the present invention, copolymer fine particles of vinyl acetate and diacetone acrylamide having a copolymerization ratio expressed by weight ratio of 100: 1 to 100: 40 are dispersed in water containing a PVA polymer. Is what you are doing.

The PVA-based resin used as a dispersant includes unmodified PVA and modified PVA. These are polymers of fatty acid vinyl esters and vinyl monomers which can be copolymerized with fatty acid vinyl esters. It can be produced by a known method such as saponification of a copolymer with a polymer.

Examples of the fatty acid vinyl ester used in the above polymerization and copolymerization include vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate, with vinyl acetate being industrially preferred. Examples of vinyl monomers used for copolymerization with fatty acid vinyl esters include unsaturated monocarboxylic acids such as crotonic acid, acrylic acid, and methacrylic acid, and esters, salts, anhydrides, amides, nitriles, and maleates thereof. Acids, itaconic acid, unsaturated dicarboxylic acids such as fumaric acid and salts thereof, unsaturated dibasic acid monoalkyl esters such as monomethyl maleate and monomethyl itaconate, α-olefins having 2 to 30 carbon atoms, alkyl vinyl ethers And vinylpyrrolidones.

As the above-mentioned polymerization method, conventionally known various methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization can be adopted. Among them, solution polymerization using methanol as a solvent is industrially preferable. Further, as the saponification method of the above-mentioned polymer and copolymer, conventionally known alkali saponification and acid saponification can be applied, and among them, a methanol solution of a polymer or methanol and water, methyl acetate, benzene, etc. Industrially preferable is a method of adding an alkali hydroxide to a mixed solution of the above to carry out alcoholysis. The modified PVA used in the present invention may be a method of saponifying a copolymer of a fatty acid vinyl ester and a vinyl monomer copolymerizable therewith, or an unmodified PVA once prepared by the above method.
May be post-modified by a reaction such as acetalization, urethanization, etherification, grafting, phosphoric esterification, acetoacetylation, etc., and particularly a polymer obtained by copolymerizing a fatty acid vinyl ester and diacetone acrylamide. The saponified product has good polymerizability in the monomer composition of the present invention and is suitable.

The degree of polymerization of the PVA resin used in the present invention,
Although the degree of saponification can be various, the viscosity of a 4% aqueous solution at 20 ° C. is 3 mPa.s. s or more, saponification degree 8
5 mol% or more is preferable. Further, the amount of the PVA-based resin in the vinyl acetate-based resin emulsion of the present invention can be various, but it is 1 to 50 parts by weight per 100 parts by weight of the copolymer fine particles of vinyl acetate and diacetone acrylamide. Parts by weight are preferred, and more preferably 2 to 4 parts by weight.
0 parts by weight, more preferably 4 to 20 parts by weight. P
If the amount of the VA resin is too small, the viscosity of the obtained emulsion is low, and the viscosity stability and mechanical stability are low. If the amount is too large, the viscosity of the emulsion becomes too high and the emulsion is difficult to handle. There is a problem that becomes.

The copolymer fine particles of vinyl acetate and diacetone acrylamide present as a dispersoid in the vinyl acetate resin emulsion of the present invention are obtained by emulsion polymerization (copolymerization) of vinyl acetate and diacetone acrylamide.
The ratio of (A) vinyl acetate monomer and (B) diacetone acrylamide monomer used in this polymerization is (A) 100 parts by weight of vinyl acetate and (B) 1 part of diacetone acrylamide. -40 parts by weight, preferably 2-30 parts by weight, more preferably 5-20 parts by weight. Therefore, the copolymerization ratio of the obtained copolymer fine particles of vinyl acetate and diacetone acrylamide is the same as the above-mentioned monomer usage ratio.

(A) 100 parts of vinyl acetate (B)
When the amount of diacetone acrylamide is less than 1 part, the effect of lowering the MFT of the obtained vinyl acetate resin emulsion is small, and if a plasticizer is not added, there is a problem in use in winter. On the other hand, when the amount exceeds 40 parts, the resulting vinyl acetate resin emulsion has high tackiness, which causes a problem in mechanical stability.

The vinyl acetate monomer and diacetone acrylamide monomer used in the above copolymerization may be added separately to a PVA-based polymer and a polymerization system containing water, or may be a mixed monomer prepared by mixing the two in advance. The effect of the present invention is not impaired even if is prepared and added. The amount of the PVA resin used here is not particularly limited, but is preferably 1 to 50 parts by weight, more preferably 2 to 4 parts by weight, based on 100 parts by weight of the total amount of the monomers.
0 parts by weight, more preferably 4 to 20 parts by weight.

As the monomer used in the emulsion polymerization, a vinyl monomer other than vinyl acetate and diacetone acrylamide can be used in combination as long as the effects of the present invention are not impaired. Examples of the vinyl monomers used herein include, for example, crotonic acid, acrylic acid, unsaturated monocarboxylic acids such as methacrylic acid and esters, salts, anhydrides, amides, nitriles, maleic acid, itaconic acid, Unsaturated dicarboxylic acids such as fumaric acid and salts thereof, monomethyl maleate, unsaturated dibasic acid monoalkyl esters such as monomethyl itaconate, and having 2 to 2 carbon atoms
30, α-olefins, alkyl vinyl ethers,
In addition to vinylpyrrolidones, ethylene, propylene, styrene and the like can be mentioned, and the addition amount is preferably 10 parts or less based on 100 parts of vinyl acetate.

Further, within a range that does not impair the effects of the present invention,
Additives such as thickeners, defoamers and crosslinking agents can be added during or after polymerization to impart desired properties to the emulsion.

[0020]

The present invention will be described in more detail with reference to the following examples. In the examples, unless otherwise specified, "%"
And "parts" are by weight. The methods for measuring various physical properties in the examples are shown below.

(1). Emulsion Polymerizability Measurement of Residual Monomer (Vinyl Acetate) Measurement was carried out according to JIS K-6828 method for measuring residual monomers of vinyl acetate resin emulsion. Coarse Particle Amount The obtained vinyl acetate resin emulsion was diluted to 3 times with water, and the diluted solution was filtered through a 100 mesh sieve.
The dry weight of what remained on the sieve was measured with an analytical balance, and the amount of coarse particles (mg / 100 g) was calculated. (2). Measurement of minimum film formation temperature Using an MFT film forming tester manufactured by Toyo Seiki Seisaku-sho, Ltd.
The obtained vinyl acetate resin emulsion was applied to a plate having a temperature gradient of −5 ° C. to 30 ° C. with a thickness of 200 μm, and the temperature of the discontinuous point between the transparent part and the opaque part of the film was read. The film formation temperature was used. (3). Overall evaluation The polymerization stability is good and the minimum film formation temperature is 10 ° C.
The following cases were evaluated as ○, and the case where either had a problem was evaluated as ×.

Example 1 A glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet was charged with 500 parts by weight of ion-exchanged water, a polymerization degree of 1,720, and a saponification degree of 98.6 mol%. PVA of 3
8 parts by weight were charged and completely dissolved at 95 ° C. This is 70
C., cooled to 0.8 parts by weight of tartaric acid and aqueous hydrogen peroxide.
5 parts by weight were added, and while stirring under a nitrogen atmosphere, a mixed monomer in which 46 parts by weight of diacetone acrylamide was previously dissolved in 416 parts by weight of vinyl acetate was continuously added over 2 hours. The temperature was raised and an aging reaction was further performed for 2 hours to complete the emulsion polymerization to obtain a vinyl acetate resin emulsion. Physical properties of the obtained emulsion were evaluated, and the results are shown in Table 1. As is clear from Table 1, the polymerization stability is good and the minimum film formation temperature is 4.8.
° C.

Example 2 The composition of the mixed monomer used in Example 1 was changed to vinyl acetate 370
Emulsion polymerization was carried out in the same manner as in Example 1 except that the weight was changed to 92 parts by weight of diacetone acrylamide, and physical properties of the obtained emulsion were evaluated. The results are shown in Table 1. As is clear from Table 1, the polymerization stability was good, and the minimum film formation temperature was -0.3 ° C.

Example 3 The composition of the mixed monomer used in Example 1 was changed to vinyl acetate 439.
Emulsion polymerization was carried out in the same manner as in Example 1 except that the parts by weight were changed to 23 parts by weight of diacetone acrylamide, and physical properties of the obtained emulsion were evaluated. The results are shown in Table 1. As is clear from Table 1, the polymerization stability was good, and the minimum film formation temperature was 8.9 ° C.

Example 4 The polymerization degree used in Example 1 was 1,720 and the saponification degree was 98.6.
Emulsion polymerization was carried out in the same manner as in Example 1 except that 38 parts by weight of PVA having a polymerization degree of 530 and a saponification degree of 88.1 mol% were used instead of 38 parts by weight of PVA, and the physical properties of the obtained emulsion were evaluated. Table 1 shows the results.
It was shown to. As is clear from Table 1, the polymerization stability was good, and the minimum film formation temperature was 4.6.

Example 5 The polymerization degree used in Example 1 was 1,720 and the saponification degree was 98.6.
A saponified product of a polymer obtained by copolymerizing vinyl acetate and diacetone acrylamide (polymerization degree 1,690, saponification degree 98.8 mol%, diacetone acrylamide modification degree 4) (0.7 mol%) Emulsion polymerization was carried out in the same manner as in Example 1 except that 38 parts by weight was used, and physical properties of the obtained emulsion were evaluated. The results are shown in Table 1. As is clear from Table 1,
The polymerization stability was good, and the minimum film formation temperature was 4.5 ° C.

Comparative Example 1 500 parts by weight of ion-exchanged water, a polymerization degree of 1,720, and a saponification degree of 98.6 mol% were placed in a glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer and a nitrogen inlet. PVA of 3
8 parts by weight were charged and completely dissolved at 95 ° C. This is 70
C., cooled to 0.8 parts by weight of tartaric acid and aqueous hydrogen peroxide.
5 parts by weight were added, and 462 parts by weight of vinyl acetate were continuously added over 2 hours while stirring under a nitrogen atmosphere, and then the temperature was raised to 80 ° C., and an aging reaction was further performed for 2 hours to carry out emulsion polymerization. The reaction was completed to obtain a vinyl acetate resin emulsion. Physical properties of the obtained emulsion were evaluated, and the results are shown in Table 1. As is clear from Table 1, the polymerization stability was good, but the minimum film formation temperature was inferior at 12.3 ° C.

Comparative Example 2 Emulsion polymerization was carried out in the same manner as in Example 1 except that the mixed monomer used in Example 1 was changed to 416 parts by weight of vinyl acetate and 46 parts by weight of n-butyl acrylate. Aggregates were generated during the polymerization, and the residual vinyl acetate monomer after the polymerization was 12.4%, and the polymerization stability was extremely poor, and no emulsion was obtained.

Comparative Example 3 Emulsion polymerization was carried out in the same manner as in Example 1 except that the mixed monomer used in Example 1 was changed to 416 parts by weight of vinyl acetate and 46 parts by weight of 2-ethylhexyl acrylate. Aggregates are generated during the polymerization, and the residual vinyl acetate monomer after the polymerization is 10.9%, and the polymerization stability is extremely poor.
No emulsion was obtained.

[0030]

[Table 1]

[0031]

As is apparent from the above description, according to the present invention, vinyl acetate having good polymerization stability and a practically sufficient level of minimum film formation temperature even without adding a plasticizer can be obtained. A resin emulsion can be provided.

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Claims (2)

[Claims] 1. The copolymerization ratio expressed by weight ratio is 100: 1 to 1.
A vinyl acetate resin emulsion comprising 100: 40 copolymer particles of vinyl acetate and diacetone acrylamide dispersed in water containing a polyvinyl alcohol polymer. 2. An emulsion polymerization of 100 parts by weight of a vinyl acetate monomer and 1 to 40 parts by weight of a diacetone acrylamide monomer in the presence of a dispersant comprising a polyvinyl alcohol polymer and water. Of producing a vinyl acetate resin emulsion.