JPH0693007A - Polyvinyl acetate-based emulsion - Google Patents

Abstract

PURPOSE:To obtain a polyvinyl acetate based emulsion having good low- temperature fluidity and low-temperature film-forming properties and capable of forming a film having high hardness and heat resistance by carrying out emulsion polymerization of vinyl acetate, etc., using a specific amount of water soluble modified starch as a protective colloid. CONSTITUTION:The polyvinyl acetate-based emulsion is obtained by subjecting 50-100wt.% vinyl acetate and 0-50wt.% one or more comonomers (e.g. acrylic acid ester) to emulsion polymerization using a water soluble modified starch (e.g. esterified starch or etherified starch) of 10-200wt.% based on total monomers as a protective colloid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetate emulsion capable of forming a film having good low-temperature film-forming property and low-temperature fluidity, high hardness and excellent heat resistance.

[0002]

2. Description of the Related Art Conventionally, polyvinyl acetate emulsions have been produced by emulsion polymerization mainly using polyvinyl alcohol (hereinafter abbreviated as PVA) as a protective colloid.

The use of PVA makes it possible to easily prepare an emulsion, obtain an emulsion having an arbitrary viscosity, and has a relatively excellent adhesive performance, but the viscosity increase rate of the emulsion at a low temperature is high. Must be warmed and is diluted with water to give fluidity. Furthermore, the polyvinyl acetate emulsion of PVA protective colloid must be added with a considerable amount of plasticizer in order to improve the low temperature film-forming property, and the addition of the plasticizer makes the coating film significantly softer and heat resistant. Became significantly poor.

On the other hand, it has been well known that starch derivatives are used as protective colloids, for example, US Pat.
No. 22322 is stable by using 0.1 to 6% by weight of a hydroxyl- or hydroxypropylated starch based on the monomer and 0.8 to 2.3% by weight of an emulsifier based on the monomer. A method of emulsion polymerizing different polymer emulsions is disclosed. This is less than 6% by weight of starch derivative per monomer.

Further, US Pat. No. 4,532,295 discloses a vinyl ester in which at least 1% by weight of a cyanoalkylated starch, a hydroxyalkylated starch and a carboxyalkylated starch is used as a protective colloid based on the weight of a monomer. A method of making a system polymer emulsion is disclosed. However, the main purpose of this is to obtain a mechanically stable polymer emulsion even without using an emulsifier, and a specific reducing agent such as peroxide and ascorbic acid is specified as a polymerization disclosure agent. Further, even in the examples, the weight per monomer of the starch derivative is studied up to 5% by weight.

Further, Japanese Patent Application Laid-Open No. 62-161848 discloses a method of using 1 to 10% by weight of alkyl or alkenyl succinic acid esterified starch as a protective colloid with respect to all monomers. The purpose is to use no emulsifier and to improve the miscibility with borax, as compared with the case of using as a protective colloid.

[0007]

Even when the etherified starch or esterified starch as described above is used as a protective colloid in an amount of 10% by weight or less based on the total amount of the monomers, for example, when all the monomers are vinyl acetate, the minimum production is required. The film temperature is 10 to 20 ° C., and when used in a room temperature drying process requiring low temperature film forming property, PV is used.
As with the A protective colloid, the addition of large amounts of plasticizer was essential. When a large amount of plasticizer was added, the hardness of the film was poor and the heat resistance was significantly inferior, resulting in the same drawbacks as the PVA protective colloid.

An object of the present invention is to provide a polyvinyl acetate emulsion which has good low-temperature fluidity and good low-temperature film-forming property without adding a plasticizer and forms a film having high hardness and heat resistance. To do.

[0009]

SUMMARY OF THE INVENTION The present invention is 50-100.
A polymer emulsion comprising, by weight, vinyl acetate and 0 to 50 weight% of at least one copolymerizable monomer, wherein the polymer emulsion serves as a protective colloid in an amount of 10 to 200 weight% of all monomers. It has been found that the minimum film forming temperature can be set to about 0 ° C. by emulsion polymerization using the water-soluble modified starch of, for example, etherified starch or esterified starch. Therefore, a plasticizer is unnecessary, and a polymer emulsion having a remarkably hard film and excellent heat resistance can be obtained.

Commercially available products corresponding to the water-soluble modified starch in the present invention are etherified starch or etherified starch modified so as to be soluble in water and partially or completely dissolved in water. As long as it is soluble in hot water and serves as a protective colloid, it can be used regardless of the type of etherification, esterification, substituents and degree of substitution.

There are various starch raw materials such as seeds of potato, sweet potato, corn, tapioca, lotus root, kwai, roots, rhizomes, etc., but any starch modified so as to be soluble in water can be used. .

Examples of monomers used for emulsion polymerization include various substances such as (meth) acrylic acid, (meth) acrylic acid ester, ethylene, vinyl chloride, and styrene, in addition to vinyl acetate.

Before the initiation of the polymerization, a peroxide or a persulfate is suitable, but it is not limited as long as radical polymerization can be initiated in an aqueous system, and a conventional method can be used as the polymerization method.

The emulsion concentration can be appropriately changed within the range of 20 to 70% by weight depending on the application, depending on the viscosity and the coating method. Further, additives can be added as necessary during or after the polymerization.

Additives used as necessary include
Commonly used plasticizers, surfactants, defoamers, preservatives, inorganic substances such as calcium carbonate, talc, and clay as fillers, and organic substances such as wheat flour, starch, and wood flour, and further, for example, dried If you need to delay the time, PV
A, an aqueous solution of starch derivative, glycerin and the like.

[0016]

The emulsion obtained by emulsion-polymerizing a vinyl acetate monomer or a copolymerizable monomer using the aqueous solution of the water-soluble modified starch of the present invention as a protective colloid has very good low-temperature fluidity. It is possible to obtain an emulsion having a good low-temperature film-forming property without affecting the low-temperature fluidity and adding a plasticizer.

Further, the main component of the water-soluble modified starch is a polymer having an α-1,4 or α-1,6 ether bond of D-glucose, which has a remarkably large molecular weight as compared with a synthetic polymer. In addition, it is considered that the main chain has a 6-membered pyranose structure linked by an ether bond, and has a cyclic structure in this main chain and a remarkably large molecular weight. Compared with a polyvinyl acetate emulsion used as a protective colloid, the film is remarkably hard and has excellent heat resistance, and it solves all the drawbacks of conventional emulsions using PVA as a protective colloid.

[0018]

【Example】

Example 1 As etherified starch, trade name “Unique Gum 301”, which is a hydroxyethylated starch made from tapioca starch as a raw material
0 "(manufactured by Matsutani Chemical Co., Ltd.) 50 g is dispersed in 250 g of water, and 8
The mixture was heated to 0 ° C. with stirring to dissolve it. Then, using 0.5 g of ammonium persulfate as an initiator, 175 g of a vinyl acetate monomer was appropriately prepared by emulsion polymerization for 3 hours to obtain a polyvinyl acetate emulsion.

Example 2 100 g of "unique gum 3010" of etherified starch was dispersed in 250 g of water and dissolved by heating and stirring to 80 ° C., and then 0.5 g of ammonium persulfate was used as an initiator.
Example 2 was carried out by adding 125 g of vinyl acetate monomer by a conventional method for 2 hours, followed by emulsion polymerization to obtain a polyvinyl acetate emulsion.

Example 3 50 g of esterified starch under the trade name "Esterin F" (manufactured by Matsutani Chemical Co., Ltd.) was dispersed in 250 g of water and dissolved by heating and stirring up to 80 ° C. Next, ammonium persulfate 0.5
Using g as an initiator, a mixture of 100 g of vinyl acetate monomer, 3 g of acrylic acid monomer and 72 g of ethyl acrylate was dropped for 3 hours and emulsion polymerization was performed to obtain a polyvinyl acetate-acrylic acid ester copolymer emulsion. Three
And

Comparative Example 1 50 g of completely saponified PVA having a degree of polymerization of 2400 was dispersed in 550 g of water and dissolved by heating and stirring up to 80 ° C. next,
Using 1.0 g of ammonium persulfate as an initiator, 360 g of vinyl acetate monomer was dropped for 3 hours and emulsion polymerization was performed to obtain a polyvinyl acetate emulsion using PVA as a protective colloid. Since the film-forming temperature of this product was 15 ° C., 60 g of DBP was mixed as a plasticizer to obtain 0 ° C., and Comparative Example 1 was obtained.

Comparative Example 2 In Example 1, the amount of "unique gum 3010" added was changed to 9 g, and the amount of the etherified starch protective colloid was reduced to about 5 parts by weight per 100 parts by weight of the monomer. The emulsion was designated as Comparative Example 2.

The non-volatile content (%), the viscosity at 30 ° C. and 0 ° C. (P / 30 ° C. and P / 0 ° C.), and the film-forming temperature (° C.) of each emulsion of Examples 1 to 3 and Comparative Examples 1 and 2 were measured. JIS
K6833 "General testing method for adhesives" and JIS
Table 1 shows the results of measurement according to K6828 “Vinyl acetate resin emulsion test method”.

Also, the hardness of the dry film (Durometer D
Hardness) is measured according to JIS K7215 “Durometer hardness of plastic” and the results are shown in Table 1.

Further, 5 layers of kraft liner paper, each emulsion of which is applied at about 50 g / m ^2, are attached to a kraft liner paper having a basis weight of 280 g / m ² , and the adhesive body after 5 days of curing is cut into a width of 25 mm and a length of 100 mm. And JIS K720
3. Bending strength (kgf / m) in the three-point bending test method with a fulcrum distance of 50 mm in accordance with “Hard plastic bending test method”
The results of measuring m ² ) are shown in Table 1.

Two layers of kraft liner paper, each emulsion of which is applied at about 50 g / m ^2, are attached to a kraft liner paper having a basis weight of 280 g / m ² , and the adhesive body after curing for 5 days is cut into a width of 25 mm and a length of 25 mm. Surface temperature of the test piece
Place it on a hot plate at 00 ° C, and then 2 on it.
Heat resistance (min / 200 ° C) was measured by placing 0 g weight, contacting the test piece with the hot plate without any gap, and applying the peeling force by hand every 30 seconds to measure the peeling time for 20 minutes. The results of the evaluation are shown in Table 1.

Also, 100 total monomers in each emulsion
Table 1 shows the theoretical value of the content by weight of the water-soluble modified starch relative to the weight.

[0028]

[Table 1]

[0029]

EFFECT OF THE INVENTION The polyvinyl acetate emulsion of the present invention has a low viscosity, good fluidity, a low film forming temperature, a hard film, and excellent heat resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C08L 31/04 LHK 6904-4J C09J 131/04 PFU 6904-4J

Claims (2)

[Claims] 1. 50% to 100% by weight of vinyl acetate and 0.
A polymer emulsion comprising at least 50% by weight of at least one copolymerizable monomer, the polymer emulsion serving as a protective colloid comprising 10 to 200% by weight of water-soluble modified starch of all monomers. A polyvinyl acetate emulsion characterized by being produced by emulsion polymerization using the same. 2. The polyvinyl acetate emulsion according to claim 1, wherein the water-soluble modified starch contains at least one of esterified starch and etherified starch.