JPH1036410A - Emulsion polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsion polymer which is excellent in low temp viscosity stability and high speed coating. SOLUTION: In an emulsion polymer of ethylenic unsatd. polymer, polyvinyl alcohol resin whose hydroxybutylvinyl ether unit content is 0.5-10mol% and saponification value is not less than 95mol% is used as a protective colloid, and 2rpm viscosity at 30 deg.C is 1-2 times the viscosity of 20rpm viscosity when 20rpm viscosity at 30 deg.C is controlled at 5,000-10,000mPa.S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an emulsion polymer having excellent low-temperature viscosity stability and high-speed coating properties.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter abbreviated as PVA) has been widely used as a protective colloid in the emulsion polymerization of ethylenically unsaturated monomers. Emulsion polymers of these ethylenically unsaturated monomers,
It is widely used in various fields such as adhesives, paints, binders, mortar admixtures, mortar splicing materials, paper, and textile processing.

[0003] When PVA is used as a protective colloid,
It is advantageous in that an emulsion polymer having high viscosity, good mechanical stability, and excellent initial adhesion can be obtained. As the PVA used as a protective colloid, a completely saponified type and a partially saponified type are generally used. The former type of PV
When A is used, an emulsion polymer excellent in high-speed coating properties can be obtained, but its low-temperature viscosity stability is inferior, and there is a problem that the viscosity increases or gels in winter, and the latter type of PVA When used, an emulsion polymer having excellent low-temperature viscosity stability can be obtained, but its high-speed coating property is inferior,
There are problems such as uneven coating and splashing of the liquid.

[0004] Also, as an emulsion polymer having improved low-temperature viscosity stability, a hydroxyalkyl vinyl ether-modified PVA comprising a hydroxyalkylene having 18 or less carbon atoms has been known (Japanese Patent Application Laid-Open No. H10-157,837). Kaisho 58
However, even when this is used, an emulsion polymer excellent in both low-temperature viscosity stability and high-speed coating property has not been obtained. As described above, at present, it is impossible to obtain an emulsion polymer excellent in both low-temperature viscosity stability and high-speed coating property.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an emulsion polymer which retains the advantages of using conventional PVA without deteriorating its advantages, and which has both excellent low-temperature viscosity stability and high-speed coating properties. Is to do.

[0006]

Means for Solving the Problems The emulsion polymer of the present invention comprises:
In order to achieve the above object, in an emulsion polymer of an ethylenically unsaturated monomer, the content of a hydroxybutyl vinyl ether unit is 0.5 to 10 mol% and the degree of saponification is 95 mol% or more. A polyvinyl alcohol-based resin is used as a protective colloid, and 30 rpm at 20 rpm
Is adjusted to 5,000-10,000 mPa · S, the viscosity at 2 ° C. at 30 ° C. is 1-2 times the viscosity at 20 rpm.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The PVA resin used as a protective colloid in the present invention has a hydroxybutyl vinyl ether unit content of 0.5 to 10 mol%, preferably 1 to 7 mol%, and a saponification degree of 0.5 to 10 mol%. 95 mol% or more, preferably 9
7 mol% or more of polyvinyl alcohol resin. When the content of the hydroxybutyl vinyl ether unit is less than 0.5, the low-temperature viscosity stability of the emulsion polymer is poor, and
When it exceeds 0 mol%, the high-speed coating property of the emulsion polymer is inferior. When the saponification degree is less than 95 mol%, the high-speed coating property of the emulsion polymer is inferior. 20 ° C of the PVA-based resin
Is 4 mPa · S or more, preferably 3 to 100 mPa · S. When the aqueous solution viscosity is less than 2 mPa · S, the function as a protective colloid is inferior.

The PVA resin used as a protective colloid in the present invention can be obtained by saponifying a copolymer of vinyl ester and hydroxybutyl vinyl ether. Examples of the vinyl ester include, but are not limited to, vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate. Vinyl acetate is industrially preferred. The copolymer of vinyl ester and hydroxybutyl vinyl ether can be obtained by a known solution polymerization method, bulk polymerization method, emulsion polymerization method, suspension polymerization method, etc., but industrially, methanol is used. Is a solution polymerization method in which is used as a solvent.

In this copolymerization, another copolymerizable ethylenically unsaturated monomer may be copolymerized as long as the effects of the present invention are not impaired. Examples of the copolymerizable ethylenically unsaturated monomer include alkyl vinyl ethers such as vinyl versatate, methyl vinyl ether and lauryl vinyl ether, (meth) acrylic acid, and maleic anhydride. Carboxylic acid-containing unsaturated monomers such as itaconic acid (anhydride) or derivatives thereof such as alkali salts or alkyl esters thereof, α-olefins such as ethylene and propylene, (meth) acrylonitrile, (meth) acrylamide or a mixture thereof. Derivatives (including those containing a sulfonic acid group or its alkali base or ammonium hydrochloride group), vinyl sulfonic acid or its alkali salt, allyl sulfonic acid or its alkali salt, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc. But not limited to. Further, those obtained by copolymerizing aldehydes such as acetaldehyde and propionaldehyde, and thiol acetic acid and mercaptopropionic acid in the presence of a thiol compound and saponifying the same are also included.

As a method for saponifying a copolymer of a vinyl ester and hydroxybutyl vinyl ether, various known methods can be employed. Industrially, a method of adding and mixing caustic soda to a methanol solution of a copolymer and saponifying it is advantageous.

The emulsion polymer of the ethylenically unsaturated monomer of the present invention can be obtained by a known emulsion polymerization method using the PVA resin as a protective colloid. Examples of the ethylenically unsaturated monomer include vinyl esters such as vinyl formate, vinyl acetate and vinyl versatate, and (meth) acrylic acid or butyl (meth) acrylate and (meth) acrylic dodecyl. Styrene monomers such as (meth) acrylic acid or alkyl esters, (meth) acrylamide or derivatives thereof (including those containing sulfonic acid or an alkali base thereof), styrene, P-styrenesulfonic acid or an alkali salt thereof And α-olefins such as ethylene and propylene, vinyl chloride, vinylidene chloride, butadiene, isoprene, chloroprene and the like, and these can be used alone or in combination of two or more. Among the above, vinyl esters,
(Meth) acrylic acid esters are preferable, and furthermore, a vinyl ester alone or in combination with (meth) acrylic esters, α-olefins such as ethylene and propylene is preferable.

Examples of the polymerization initiator for the emulsion polymerization of ethylenically unsaturated monomers include known persulfates, hydrogen peroxide, and the like.
Examples include peroxide-based and azo-based ones. Further, it may be used in a redox system in combination with a known reducing agent.

In the polymerization of the ethylenically unsaturated monomer, the ethylenically unsaturated monomer is usually added to the polymerization system all at once, dividedly or continuously. Further, an ethylenically unsaturated monomer emulsified in advance with the PVA-based resin may be added. The above P during polymerization of the ethylenically unsaturated monomer
The addition amount of the VA-based resin is not particularly limited and is determined according to the purpose, but is usually 1 to 30 parts by weight based on 100 parts by weight of the ethylenically unsaturated monomer. Preferably it is 2 to 20 parts by weight. In addition, if necessary, the PV
The A-based resin may be added as a powder or an aqueous solution after the completion of the emulsion polymerization. In the case of emulsion polymerization, a water-soluble polymer such as conventionally known PVA, starches, cellulose derivatives, polyacrylic acid soda and the like, if necessary, other than the PVA-based resin, as long as the effects of the present invention are not impaired. And anionic, nonionic or cationic surfactants can be used alone or in combination of two or more. The solid content concentration of the emulsion polymer is usually 30 to 60% by weight.

In order to exhibit the effects of the present invention, the emulsion polymer of the ethylenically unsaturated monomer must be at 20.degree.
When the viscosity at rpm is adjusted to 5,000 to 10,000 mPa · S, the viscosity at 2 ° C. at 30 ° C. needs to be 1 to 2 times the viscosity at 20 rpm, preferably 1 to 2.
It is 1.8 times. The viscosity of 2 rpm at 30 ° C is 20 rpm
If the viscosity of the emulsion polymer exceeds twice, there is a possibility that when the emulsion polymer is coated at a high speed, glue may be spattered or the coating amount may be uneven.

The viscosity at 20 rpm at 30 ° C. is 5,0
As a method for adjusting the pressure to 00 to 10,000 mPa · S, a conventionally known method such as dilution or concentration may be used.

The emulsion polymer of the ethylenically unsaturated monomer of the present invention may contain, if necessary, known plasticizers, film-forming auxiliaries, fillers, fillers, pigments, extenders, defoamers, freezers. Inhibitors, preservatives, and the like can be appropriately added within a range that does not impair the effects of the present invention.

Although the function of the present invention is not always clear, by modifying PVA by copolymerizing hydroxybutyl vinyl ether, the crystallization of PVA due to hydrogen bonding is reduced, and the low-temperature viscosity stability is improved. At the same time, it is considered that emulsifying properties that cannot be achieved with general-purpose PVA impart excellent emulsion coating properties to emulsion polymers.

[0018]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The viscosity, low-temperature viscosity stability and high-speed coating property of the obtained emulsion polymer were measured and evaluated by the following methods. (1) Viscosity of emulsion polymer The viscosity was measured at 30 ° C. using a B-type viscometer at a rotation speed of 2
It was measured at rpm and 20 rpm. (2) Low Temperature Viscosity Stability of Emulsion Polymer The viscosities at 1 ° C. and 24 hours after standing at 5 ° C. were measured. The low-temperature thickening magnification was calculated by the following equation to evaluate low-temperature viscosity stability. Low temperature thickening ratio = viscosity (after 24 hours) / viscosity (after 1 hour) ○: Low temperature thickening ratio is less than 3 times ×: Low temperature thickening ratio is 3 times or more

(3) High-speed coating property The adhesive winding roll and the adhesive coating roll are brought into contact with each other, and are rotated in the opposite direction at 330 rpm for 30 minutes. Was adhered to an aluminum foil disposed in close proximity to the sample, and the amount was measured and evaluated. ：: The amount of scattering is less than 10 mg. X: The amount of scattering is 10 mg or more. ：: Both low-temperature viscosity stability and high-speed coating property of the emulsion polymer are excellent (○). X: Either low-temperature viscosity stability or high-speed coating property of the emulsion polymer is inferior, or both are inferior.

Example 1 (Production of hydroxybutyl vinyl ether-modified PVA)
6650 parts by weight of vinyl acetate, 350 parts by weight of hydroxybutyl vinyl ether (hereinafter abbreviated as HBVE) and 3000 parts by weight of methanol were charged into a polymerization vessel, and the temperature was increased while stirring the system under nitrogen. C., 4.2 parts by weight of azoisobutyronitrile were added to methanol 200.
A solution dissolved in parts by weight was added, and polymerization was started. When the solid content concentration reached 60% by weight, the content was cooled to terminate the polymerization. Methanol vapor is blown into the obtained polymer solution to remove unreacted vinyl acetate.
Solution was obtained. Then, methanol was added to this solution,
After adjusting the concentration of the polymer to 35% by weight, 6,000 parts by weight of the solution was kept at 40 ° C., and the mixture was stirred with a solution prepared by dissolving 12 parts by weight of sodium hydroxide in hydrated methanol. After mixing, the polymer solution gelled in about 8 minutes. This gel was pulverized 60 minutes later, washed well with methanol, and dried under a nitrogen stream at 100 ° C. to obtain 1,100 parts by weight of a modified granular PVA resin in the form of white granules. This resin is
The degree of HBVE modification is 3.4 mol% and the degree of saponification is 98.
The viscosity of the aqueous solution having a concentration of 5 mol% and a concentration of 4% by weight at 20 ° C. was 15 mPa · S as measured by a rotational viscometer.

(Emulsion Polymerization of Vinyl Acetate) In a 2-liter glass container equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 500 g of ion-exchanged water was added to the above modified P.
A solution in which 40 g of VA resin was dissolved was charged, and 1 g of sodium acetate, 1 g of tartaric acid, 1 g of hydrogen peroxide and 10 g of vinyl acetate were added thereto, and emulsion polymerization was started at 75 ° C. with stirring. Further, 420 g of vinyl acetate was added thereto over 2 hours to continue the emulsion polymerization, and then heated at 80 ° C. for 2 hours with stirring to obtain an emulsion polymer. Solids concentration: 48.3% by weight, viscosity at 30 rpm at 20 rpm: 6,500 m
The viscosity at Pa · S and 2 rpm was 12,000 mPa · S. The low-temperature thickening ratio was 2.1 times, and the high-speed coating property was 7 mg.

Examples 2 and 3 and Comparative Examples 1 to 4 Emulsion polymerization of vinyl acetate was carried out by using various HBVE-modified PVAs or unmodified PVAs shown in Table 1 obtained in the same manner as in Example 1. Table 2 shows the results of evaluation of the obtained emulsion polymer. Examples 2 and 3 were excellent in low-temperature viscosity stability and high-speed coating property. In Comparative Examples 1 to 4, one or both of the low-temperature viscosity stability and the high-speed coating property were inferior.

[0023]

[Table 1]

Example 4 40 g of the HBVE-modified PVA obtained in Example 1 was dissolved in 550 g of ion-exchanged water, and charged in a 2-liter autoclave equipped with a thermometer and a nitrogen inlet. After adjusting the pH to 4 with dilute sulfuric acid, 570 g of vinyl acetate was charged, and the pressure of ethylene was increased to 45 kg / cm ² G. After the temperature was raised to 60 ° C., emulsion polymerization was started with a hydrogen peroxide-Rongalit redox initiator. After 3 hours, the polymerization was completed. Solids concentration 51.8% by weight, 20 at 30 ° C.
The viscosity at rpm was 5,500 mPa · S, and the viscosity at 2 rpm was 9,400 mPa · S. In addition, as shown in Table 2, the product had a low-temperature thickening ratio of 2.2 times and a high-speed coating property of 8 mg.

Example 5 A 2-liter glass container equipped with a reflux condenser, a dropping funnel, a thermometer and a nitrogen inlet was charged with 500 g of ion-exchanged water.
Was charged with a solution in which 40 g of the modified PVA-based resin obtained in Example 1 was dissolved, and 8.3 g of vinyl acetate and n-acrylic acid were added thereto.
Then, 1.7 g of -butyl was added, and emulsion polymerization was started at 75 ° C under stirring. Further, 350 g of vinyl acetate and 70 g of n-butyl acrylate were added thereto over 2 hours, and emulsion polymerization was continued, followed by heating at 80 ° C. for 2 hours with stirring to obtain an emulsion polymer. Solids concentration 48.5 wt%, viscosity at 20 rpm at 30 ° C. is 5,000 mPa · S, 2 rpm
m was 8,500 mPa · S. Table 2
As shown in Table 2, the low-temperature thickening ratio was 2.1 times, and the high-speed coating property was 8 mg.

[0026]

[Table 2]

[0027]

As is clear from the above description, according to the present invention, while maintaining the advantages of using conventional PVA without impairing it, both low-temperature viscosity stability and high-speed coating properties are excellent. An emulsion polymer can be provided.

Claims (1)

[Claims] 1. An emulsion polymer of an ethylenically unsaturated monomer, comprising a polyvinyl alcohol resin having a hydroxybutyl vinyl ether unit content of 0.5 to 10 mol% and a saponification degree of 95 mol% or more. It is used as a protective colloid and has a viscosity of 5,000 at 30 ° C. and 20 rpm.
An emulsion polymer, wherein the viscosity at 2 rpm at 30 ° C. when adjusted to に 10,000 mPa · S is 1 to 2 times the viscosity at 20 rpm.