JPS6365689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high viscosity polymer emulsions by adding glyoxalated polyvinyl alcohol to the polymer emulsion. Polymer emulsions, such as vinyl acetate resins,
Emulsions such as acrylic ester resins and vinyl chloride resins, ethylene-vinyl acetate copolymer emulsions, and vinyl acetate-acrylic ester copolymer emulsions are widely used in paints, adhesives, and other applications. When used in such applications, the viscosity of the emulsion is a characteristic that has a large effect on workability, mechanical suitability, finished condition, adhesion, etc., and it is important to adjust it to the desired viscosity through simple operations. This is a serious issue. For example, when applying an emulsion in the form of a thin film, if the emulsion is diluted with water to reduce the solid content concentration of the emulsion, the viscosity of the emulsion itself decreases, causing problems such as a decrease in mechanical suitability, adhesiveness, and stability. . Furthermore, when a highly viscous emulsion is required, the solids concentration of the emulsion must be extremely high, and emulsions with an extremely high solids content have manufacturing problems and are not easily available. . Therefore, a method that is less dependent on the solid content concentration of the emulsion and allows the viscosity to be adjusted arbitrarily is preferred. As a conventional technique related to such a method, a method is known in which methyl cellulose, hydroxyethyl cellulose, sodium polyacrylate, polyvinyl alcohol, etc. are added to the emulsion as a thickener to thicken the emulsion. Although this method has the advantage that the viscosity of the emulsion can be adjusted over a fairly wide range by adjusting the amount of the thickener added, the resulting emulsion has a large structural viscosity index and is not sticky. The emulsion has disadvantages of sagging and poor stability over time, and these disadvantages have a large effect when the emulsion is used for paints, adhesives, etc. As a result of intensive studies to solve the above-mentioned problems, the present inventors found that glyoxalated polyvinyl alcohol (hereinafter abbreviated as GX-modified PVA) modified with glyoxal was used as a polymer emulsion, especially ethylene-vinyl acetate. When added to a copolymer emulsion afterward, it has a more pronounced viscosity-enhancing effect than conventionally known thickeners, so the range in which the viscosity can be adjusted is expanded, and the viscosity changes little over time, meaning it has excellent stability. They found that it has advantages such as having a small structural viscosity index and being sticky, so it has good fluidity and good initial tack, and they were able to complete the present invention. Such effects can only be obtained by post-adding GX-modified PVA to the polymer emulsion, and in the method of using GX-modified PVA as an emulsifier during emulsion production, due to the relationship with the control of the emulsion polymerization reaction, GX cannot be adjusted arbitrarily and is also used as an emulsifier.
Since the behavior of modified PVA and GX modified PVA when added later is different, it is difficult to obtain a sticky emulsion with a small structural viscosity index as in the method of the present invention. The high viscosity polymer emulsion obtained by the method of the present invention, especially the ethylene-vinyl acetate copolymer emulsion, has a high viscosity, a small structural viscosity index, and is sticky, so that it can be used as a paint. Improved leveling if applicable. 2. When used as an adhesive or coating agent, it can have effects such as improving suitability for high-speed rolls (coating workability) and improving adhesive strength. The GX-modified PVA used in the present invention is, for example, polyvinyl alcohol with a degree of saponification of 70 to 97 mol% and an average degree of polymerization of 1000 to 3000, methanol, ethanol,
It is produced by adding an organic solvent such as methyl acetate or acetone and a 40% aqueous solution of glyoxal, stirring and mixing at 20 to 40°C for about 1 hour, and then drying. The amount of glyoxal added is appropriately selected within a range that modifies the glyoxal content by 0.005 to 10 parts by weight based on 100 parts by weight of PVA. If it exceeds 10 parts by weight, it becomes water-insoluble, which is undesirable, and if it is less than 0.005 parts, no effect can be obtained. The particle size of the obtained powdered GX-modified PVA is 10 meshes or less, preferably in the range of 40 to 100 meshes, so that when it is added to a polymer emulsion as a powder, it does not become lumpy and remains stable when cold or hot. It is also suitable because of its good solubility. Examples of the polymer emulsion used in the present invention include ethylene-vinyl acetate copolymer emulsion and acrylic ester copolymer emulsion, particularly ethylene-vinyl acetate copolymer emulsion (ethylene content of 5 to 50% by weight). %) are preferred, as mentioned above. The optimum amount of GX-modified PVA to be added to the polymer emulsion varies depending on the viscosity of the target emulsion, the type of emulsion, the solid content of the resin, the type of GX-modified PVA, etc., but it is generally 100 parts by weight of the polymer emulsion. On the other hand, powdered GX-modified PVA can be selected from the range of 0.05 to 5 parts by weight. If it is less than 0.05 parts by weight, the thickening effect tends to be small, and if it is more than 5 parts by weight, the viscosity tends to be too high and fluidity tends to be poor. Depending on the amount added above, the emulsion viscosity can be adjusted to 1000~
200000cps (25℃, BH type viscometer, rotor No.1~
6. The rotation speed can be adjusted over a wide range (4 rpm). When carrying out the method of the present invention, no special equipment is required; a mixing tank equipped with a stirrer is sufficient.
After putting the polymer emulsion into the mixing tank, add powdered GX-modified PVA while stirring, and mix for about 1 hour.
It can be obtained by stirring for ~2 hours. There is no problem with the temperature at room temperature, but the stirring time can be shortened by heating to about 60°C. Next, the present invention will be specifically explained using examples. In the examples, "parts" refer to "parts by weight." Example 1 In a mixing tank equipped with a stirrer, an ethylene-vinyl acetate copolymer emulsion (ethylene content 19.6% by weight, 25°C, viscosity 5300 cps measured with a BH type viscometer at rotor No. 2, rotation speed 4 rpm, Concentration 56.4%)
100 parts and then 2.5 parts of GX-modified PVA (PVA component saponification degree 78 mol%, average polymerization degree 1700) powder modified with 3% glyoxal were added at once, and after stirring for 2 hours, the mixture was taken out and the viscosity was measured.
120000cps (25℃, Rotor No. by BH type viscometer)
6. The number of rotations was 4 rpm), the structural viscosity index (TI) was 0.47, and it was sticky and had a viscosity suitable for adhesive. TI = log (viscosity measured at 2 rpm / viscosity measured at 20 rpm) When this emulsion was applied as a thin film on a glass plate, it became a uniform coating, and the undissolved GX modification
No PVA particles were observed. Further, the viscosity of the emulsion was measured after being left at room temperature for one month, and it was found to be stable at 117,000 cps with no change. Example 2 Same as Example 1 except that (meth)acrylic acid ester copolymer emulsion (Movinyl 700, manufactured by Hoechst Synthesis Co., Ltd., viscosity 60 cps) was used in place of the ethylene-vinyl acetate copolymer emulsion of Example 1. A uniform high viscosity emulsion with a viscosity of 19,000 cps, stickiness, and TI=0.84 was obtained. The viscosity of this emulsion after being left at room temperature for one month was 17,000 cps. Control Example 1 Methyl cellulose (Tyrose MH-4000K, Hoechst product) powder was added to 100 parts of the ethylene-benyl acetate copolymer emulsion used in Example 1.
1.0 part was added at once and stirred for 4 hours, but since some undissolved portions remained, stirring was continued for an additional 2 hours to obtain a highly viscous emulsion. The resulting emulsion had a viscosity of 80,000 cps and a TI of 0.50, but was not sticky and crumbly. When this emulsion was applied to a glass plate in the same manner as in Example 1, a uniform coating film was obtained. The viscosity of the emulsion was measured after two days and was 85,000 cps, 80,000 cps after 14 days, and 75,000 cps after one month. The stability over time showed poor results. Control Example 2 2.5 parts of polyvinyl alcohol (saponification degree 78 mol%, average degree of polymerization 1700) powder was added at once to 100 parts of the ethylene-vinyl acetate copolymer emulsion used in Example 1, and stirred for 4 hours, but no dissolution occurred. Since some portions were warm, stirring was continued for an additional 2 hours to obtain a highly viscous emulsion. The viscosity of the emulsion obtained is
It was 100000cps and sticky with TI=0.55.
When this emulsion was applied to a glass plate in the same manner as in Example 1, a uniform coating film was obtained. However, when the viscosity of the emulsion was measured two days later,
It was 120,000cps, 100,000cps after 14 days, and 80,000cps after one month. The stability over time showed poor results. The results of Examples 1 and 2 and Control Examples 1 and 2 are summarized in Table 1. 【table】

Claims (1)

[Claims] 1. Ethylene-vinyl acetate copolymer emulsion or acrylic ester copolymer emulsion
A method for producing a high viscosity polymer emulsion, which comprises adding and mixing 0.05 to 5 parts by weight of glyoxalated polyvinyl alcohol to 100 parts by weight. 2. The production method according to claim 1, wherein the glyoxalized polyvinyl alcohol is a glyoxalated polyvinyl alcohol modified with a glyoxal component of 0.005 to 10% by weight (based on the polyvinyl alcohol component).