JPH06322031A - Production of high-solid water-base emulsion - Google Patents

Abstract

PURPOSE:To prevent the viscosity increase of a liq. polymn. system during polymn. CONSTITUTION:A high-solid water-base emulsion mainly comprising an ethylene- vinyl ester copolymer contg. 5-40wt.% ethylene units is produced in two steps: the first step wherein 40-90wt.% of a vinyl ester to be copolymerized, an emulsifier in an amt. of 2.5-5.0 pts.wt. based on 100 pts.wt. the total vinyl ester to be copolymerized, and water are mixed by stirring to give an emulsion wherein the max. diameter of dispersed particles is 50mum or lower and at least 90% (in number) of particles having diameters of 0.1mum or higher have diameters of 5mum or lower; and the second step wherein the emulsion formed at the former step is polymerized together with the rest, 10-60wt.%, of the total of the total of the vinyl ester used in the polyinesization in the presence of a redox catalyst at 30-80 deg.C under an ethylene pressure of 10-100kg/cm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high solid water content emulsion. More specifically, the present invention relates to a method for producing a high-solids water-based emulsion containing a vinyl ester-based copolymer as a main component.

[0002]

2. Description of the Related Art A high solid water content emulsion containing a vinyl ester copolymer as a main component is widely used as an adhesive. Here, a high solid content water-based emulsion having a solid content concentration of 65 to 70% by weight requires a small drying energy when used as an adhesive and is known as an extremely superior adhesive. However, in the conventional method for producing a high solid content water-based emulsion containing a vinyl ester copolymer as a main component, the viscosity of the polymerization solution increases during the polymerization reaction due to the nature of high solid content, and the slow heating There was a problem that the ability was insufficient, a uniform and efficient polymerization reaction was hindered, and in a remarkable case, the polymerization reaction could not be continued.

[0003]

In view of the above situation, the main problem to be solved by the present invention is that the solid content concentration is 6%.
A method for producing a high-solids water-based emulsion having a concentration of about 5 to 70% by weight, which is to provide a method for producing a high-solids water-based emulsion without an increase in the viscosity of a polymerization solution during a polymerization reaction.

[0004]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems.

That is, according to the present invention, the ethylene unit is 5-4.
The present invention relates to a method for producing a high solid content water-based emulsion containing an ethylene-vinyl ester copolymer containing 0% by weight as a main component, the method including a first step and a second step described below. First step: 40 to 90 of all vinyl esters used for polymerization
A step of obtaining an emulsified dispersion by stirring and mixing vinyl ester corresponding to wt%, 2.5 to 5.0 parts by weight of an emulsifier and water per 100 parts by weight of all vinyl esters to be subjected to polymerization. The step in which the maximum particle size of dispersed particles in the emulsified dispersion is 50 μm or less, and 90% or more of the particles having a particle size of 0.1 μm or more have a particle size of 5 μm or less. Using the emulsion dispersion obtained in the first step, in the presence of a redox polymerization catalyst, under the conditions of a polymerization temperature of 30 to 80 ° C. and an ethylene pressure of 10 to 100 kg / cm ² , 10 to 60 weight of all vinyl esters to be subjected to polymerization. % To add and polymerize

The details will be described below. The copolymer, which is the main component of the aqueous emulsion of the present invention, contains an ethylene unit and a vinyl ester unit as essential component units. Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl laurate, vinyl versatate and the like. Among them, vinyl acetate or a combination of vinyl acetate and another vinyl ester is preferable. The copolymer of the present invention is an ethylene-vinyl ester copolymer containing 5 to 40% by weight of ethylene unit. When the ethylene unit is too small, the film forming temperature becomes high and problems such as poor adhesion occur when used as an adhesive in winter. On the other hand, when the ethylene units are excessive, the copolymer becomes too soft, its cohesive force is reduced, and the adhesive strength when used as an adhesive is reduced.
In the copolymer of the present invention, a component containing a copolymerizable component unit other than a vinyl ester unit and an ethylene unit, for example, a component containing an amide group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, an N-methylol group or the like. Units may be included.

As the emulsifier of the present invention, it is preferable to use both a partially saponified polyvinyl alcohol and a polyoxyethylene nonionic surfactant. The partially saponified polyvinyl alcohol has an average degree of polymerization of 300 to 1
000 is preferable, and the average degree of polymerization is 400 to 800.
Are most preferred. As long as the average degree of polymerization is within these ranges, polyvinyl alcohol having a degree of polymerization of 1000 or more may be used in combination. If the average degree of polymerization is too small, lees are produced, while if the average degree of polymerization is too large, the viscosity may increase. Here, the partial saponification means that the saponification degree is usually less than 96 mol%, preferably 70 to 96 mol%. If the degree of saponification is too high, phase separation or precipitation may occur in the emulsion. Further, as the polyoxyethylene nonionic surfactant, HLB is 13 to
Those having an HLB of 19 are preferable, and those having an HLB of 15 to 18 are most preferable. Here, HLB is an index widely used in the art to indicate the balance between the hydrophilic group and the lipophilic group of the surfactant. If the HLB is too small, the particle size of the obtained emulsion particles becomes large, and the initial adhesiveness when used as an adhesive may be poor. On the other hand, when the HLB is too large, the stability of the emulsion during the polymerization reaction is poor and the lees may be generated. Specific examples of the polyoxyethylene nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene fatty acid ether, and polyoxyethylene sorbitan fatty acid ether.

In the first step of the present invention, 40 to 90% by weight, preferably 5% by weight, of all vinyl esters to be subjected to polymerization.
2.5 to 100 parts by weight of vinyl ester corresponding to 0 to 80% by weight and all vinyl esters to be subjected to polymerization
It is necessary to stir and mix 5.0 parts by weight, preferably 2.7 to 4.6 parts by weight of emulsifier and water. If the proportion of vinyl ester used here is too small, a large amount of lees will be generated,
On the other hand, when the ratio is too large, the viscosity of the emulsion becomes too large. Further, if the proportion of the emulsifier used here is too small, the stability of the emulsion will be reduced due to phase separation or precipitation, and the emulsion will also have residue. On the other hand, when the ratio is too large, the viscosity of the emulsion becomes too large.

The emulsified dispersion obtained in the first step of the present invention has a maximum dispersed particle size of 50 μm or less, preferably 20 μm.
90% or more, preferably 97% or more, of the number of particles having a particle size of not more than 0.1 and having a particle size of not less than 0.1μ must have a particle size of not more than 5μ. When a large number of particles having a large particle size are contained without using the present invention, the viscosity of the emulsion becomes excessive. The particle size is measured by a phase contrast microscope observation photograph of the emulsion dispersion.

In the first step, it is preferable to stir and mix under the conditions of the following formulas (1) and (2), and most preferably to stir and mix under the conditions of the following formulas (3) and (4). preferable. This makes it possible to prepare an emulsified dispersion liquid that satisfies the above-mentioned conditions of the present invention.

0.1 ≦ N ² D ³ ≦ 3.5 (1) 0.01 ≦ R / V ≦ 0.2 (2) 0.12 ≦ N ² D ³ ≦ 3.0 (3) 0.04 ≦ R / V ≦ 0.1 (4)

Here, N is the number of rotations of the stirring blade (times / second)
Represents the maximum diameter (m) of the stirring blade on the plane of rotation, R represents the volume (m ³ ) of the rotor formed by the rotation of the stirring blade, and V represents the emulsified dispersion that is stirred and mixed. It represents the volume (m ³ ) of the liquid when it was allowed to stand. For example, in the case of a stirring blade having a stirring axis on the vertical center line of a rectangle of length L (m) × width W (m), D = W, R = 0.25πW ² L (π = 3.
14).

The second step of the present invention uses the emulsion dispersion obtained in the first step, in the presence of a redox polymerization catalyst, at a polymerization temperature of 30 to 80 ° C. and an ethylene pressure of 10 to 100 kg / c.
Under the condition of m ² , it is a step of adding 10 to 60% by weight of all vinyl esters to be polymerized and polymerizing.

Among the redox polymerization catalysts, examples of the oxidizing agent include hydrogen peroxide, t-butyl peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and the like. The amount of the oxidizing agent used is usually 0.01 to 0.15 part by weight, based on 100 parts by weight of all vinyl esters used for the polymerization. Among the redox polymerization catalysts, examples of the reducing agent include sodium (or zinc) formaldehyde sulfoxylate and glyoxal sodium bisulfite.
The amount of the reducing agent used is usually 0.05 to 0.75 part by weight per 100 parts by weight of the total vinyl ester used for the polymerization.

The polymerization temperature is 30 to 80 ° C., preferably 4
It is 0 to 70 ° C. If the temperature is too low, the progress of the polymerization reaction is slow. On the other hand, if the temperature is too high, the molecular weight of the produced polymer is too small, the cohesive force of the polymer is lowered, and the performance as an adhesive is lowered. The ethylene pressure during polymerization is 5 to 150 kg / cm ² , preferably 10 to 100 kg
/ Cm ² . If the pressure is too low, the stability of the emulsion will be poor, while if the pressure is too high, the amount of ethylene copolymerized will increase, the cohesive force of the polymer will decrease, and the performance as an adhesive will decrease.

According to the invention, the viscosity is usually between 500 and 80.
An aqueous emulsion of 00 cps, preferably 800-6000 cps can be obtained.

[0017]

EXAMPLES Next, the present invention will be described with reference to examples. The evaluation method is as follows. (1) Solid content of emulsion:% by weight of residue after drying at 105 ° C. for 2 hours (2) Viscosity of emulsion BL viscometer, 60 rotations, 25 ° C. (3) Dregs in the emulsion The emulsion was filtered through a 300-mesh wire mesh, 105
The residue (based on the emulsion weight ppm) on the wire net after drying at 0 ° C. for 2 hours was used as the lees.

Example 1 In a pressure-resistant reactor equipped with a stirrer, 68.7 l of water, 0.26 l of 50% by weight acetic acid (pH buffer), partially saponified polyvinyl alcohol (polymerization degree 1750, saponification degree 88 mol% 0 0.5 kg and 2 kg having a degree of polymerization of 350 and a degree of saponification of 88 mol% were used.The average degree of polymerization was 630, corresponding to 1.67 parts by weight per 100 parts by weight of all vinyl acetate to be subjected to the polymerization) and polyoxyethylene. Charge 3 kg of nonyl phenyl ether (HLB 16.2) (corresponding to 2 parts by weight per 100 parts by weight of all vinyl acetate used for polymerization),
The mixture was stirred and mixed at a temperature of ° C to obtain a uniform aqueous solution. To the aqueous solution were added 2.8 g of ferrous sulfate, which is a reducing agent for redox catalyst, and 1.3 l of a 14% by weight aqueous solution of sodium formaldehyde sulfoxylate. Next, 74.5 kg of vinyl acetate was added to the obtained liquid (5% of total vinyl acetate used for polymerization).
(Corresponding to 0% by weight) was added and mixed with stirring to obtain an emulsion dispersion. At this time, the stirring blades and stirring conditions used were N
² D ³ = 0.824 m ³ / s ² , R / V = 0.072 m
It was ³ / m ³ . Further, in the obtained emulsified dispersion liquid, 99% or more of the number of particles having a particle size of 0.1 μ or more among the dispersed particles therein had a particle size of 5 μ or less. Next, the inside of the reaction vessel containing the above emulsified dispersion liquid was replaced with nitrogen and then with ethylene, and the ethylene pressure was set to 45 kg / cm ² while raising the temperature to 60 ° C.
Hydrogen peroxide aqueous solution (oxidizing agent for redox catalyst) 9.7
1 was added over 6 hours, and then 4.6 l of 3.2 wt% hydrogen peroxide aqueous solution was added over 2 hours.
2.7 l of a 7% by weight aqueous sodium formaldehyde sulfoxylate solution (a reducing agent for a redox catalyst) was added over 7 hours. Meanwhile, the remaining vinyl acetate is 74.5k
The polymerization reaction was carried out by adding g at a feed rate of 12.4 kg / H. The conditions and results are shown in Table 1.

Comparative Examples 1 to 6 The same procedure as in Example 1 was carried out except that the conditions shown in Table 1 were used. The conditions and results are shown in Table 1.

The results show the following. In the examples satisfying the conditions of the present invention, all the evaluation items show satisfactory results. On the other hand, the comparative examples lacking any of the conditions of the present invention show unsatisfactory results as follows. In Comparative Example 1 in which the ratio of vinyl acetate used in the first step to the total vinyl acetate was too small, a large amount of lees were generated. In Comparative Example 2 in which the ratio was excessive, the viscosity of the obtained emulsion was excessive. Comparative Example 3 in which the ratio of the emulsifier used in the first step to the total vinyl acetate was too small was 50,000 ppm.
It produced m-scale dregs and was not worthy of evaluation. In Comparative Example 4 in which the ratio was excessive, the viscosity of the obtained emulsion was excessive. The emulsified dispersion obtained in the first step did not satisfy the conditions of the present invention, and the N ² D ³ value, which is a stirring condition, was too small or too large, so that Comparative Example 5 contained a large number of oversized particles.
Alternatively, Comparative Example 6 has an excessively high viscosity of the obtained emulsion.

[0021]

[Table 1] -------------------------------------------- Examples Comparative Example 1 1 2 3 1st Process Vinyl acetate usage ratio wt% * 1 50 25 100 50 Emulsifier usage ratio wt% * 2 3.67 3.67 3.67 2.3 Specific particle ratio of emulsified dispersion% * 3>99>99>99> 99 Maximum particle size of emulsified dispersion particles μ 12 12 12 12 Second step N ² D ³ 0.824 0.824 0.824 0.824 R / V 0.072 0.060 0.050 0.072 Ethylene wt% in copolymer 20.0 19.9 18.1-Evaluation emulsion solids wt% 67.6 67.2 67.5-Emulsion viscosity cps 2440 331> 10000-lees in emulsion ppm 181 9602 1500 50000 -----------------------------------------------------

[0022]

[Table 2] ---------------------------------------- Comparative Example 4 5 6 1st step Vinyl acetate use ratio wt% * 1 50 50 50 Emulsifier usage ratio wt% * 2 6.0 3.67 3.67 Specific particle ratio of emulsified dispersion% * 3> 99 85 60 Maximum particle size of emulsified dispersion μ 12 42 21 2nd step N ² D ³ 0.824 0.080 3.796 R / V 0.072 0.072 0.063 Ethylene in copolymer wt% 18.2 14.2 14.2 Evaluation solid content wt% of emulsion 67.1 67.3 67.0 Viscosity of emulsion cps ＞ 10000 ＞ 10000 ＞ 10000 Minerals in emulsion ppm 112 183 22 ----- −−−−−−−−−−−−−−−−−−−−−−−−−

* 1 Use ratio of vinyl acetate Proportion used in the first step of all vinyl acetate used for polymerization * 2 Use ratio of emulsifier Ratio of emulsifier used for 100 parts by weight of all vinyl acetate used for polymerization * 3 Emulsion dispersion Specific particle ratio of the number of particles having a particle size of 5μ or less among particles having a particle size of 0.1μ or more in the emulsion dispersion

[0024]

As described above, according to the present invention, a method for producing a high solid content water-based emulsion having a solid content concentration of about 65 to 70% by weight without increasing the viscosity of a polymerization solution during a polymerization reaction. It was possible to provide a method for producing a high solid content water-based emulsion.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Choji Tomizawa 5-1 Anesaki Kaigan, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (72) Inventor Yasuo Kaneshima 1-5 5 Anezaki-kaigan, Ichihara, Chiba Sumitomo Chemical Within Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A method for producing a high solids water-based emulsion comprising an ethylene-vinyl ester copolymer containing 5 to 40% by weight of an ethylene unit as a main component, which comprises the following first step and second step. Production method. First step: 40 to 90 of all vinyl esters used for polymerization
A step of obtaining an emulsified dispersion by stirring and mixing vinyl ester corresponding to wt%, 2.5 to 5.0 parts by weight of an emulsifier and water per 100 parts by weight of all vinyl esters to be subjected to polymerization. The step in which the maximum particle size of dispersed particles in the emulsified dispersion is 50 μm or less, and 90% or more of the particles having a particle size of 0.1 μm or more have a particle size of 5 μm or less. Using the emulsion dispersion obtained in the first step, in the presence of a redox polymerization catalyst, under the conditions of a polymerization temperature of 30 to 80 ° C. and an ethylene pressure of 10 to 100 kg / cm ² , 10 to 60 weight of all vinyl esters to be subjected to polymerization. % To add and polymerize 2. The method according to claim 1, wherein in the first step, stirring and mixing are performed under the conditions of the following formulas (1) and (2). 0.1 ≦ N ² D ³ ≦ 3.5 (1) 0.01 ≦ R / V ≦ 0.2 (2) Here, N represents the number of revolutions (times / second) of the stirring blade, and D represents stirring. It represents the maximum diameter (m) of the blade on the plane of rotation, R represents the volume (m ³ ) of the rotor formed by the rotation of the stirring blade, and V represents the volume of the emulsified dispersion liquid that is agitated and mixed when standing. Represents (m ³ ). 3. The method according to claim 1, wherein the emulsifier used in the first step is partially saponified polyvinyl alcohol and a polyoxyethylene nonionic surfactant.