JPH0225858B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cement composition that improves adhesion. Specifically, it relates to a cement composition obtained by adding an emulsion containing cationized polyvinyl alcohol as a stabilizer to cement and kneading it with water. Conventionally, ethylene-vinyl acetate emulsion, acrylic emulsion, styrene-butadiene latex, etc. are mixed with cement and used for adhesion of old concrete to new concrete, adhesion of tiles to concrete, adhesion of exterior wall paint to concrete, etc. ing. Furthermore, it has long been known that by kneading a synthetic resin emulsion into cement, bending strength, compressive strength, adhesive strength, etc. can be improved. For example, regarding vinyl acetate emulsion, JMGeist et al., Ind.
Eng.Chem, Vol. 45, pp. 759-767 (1953), French Patent No. 1455910 (1966) regarding ethylene-vinyl acetate copolymer emulsion, and Japanese Patent Publication No. 1455910 (1966) regarding acrylic emulsion. The effect of modification as a cement product can certainly be seen. However, if emulsion is mixed into cement, it becomes extremely expensive, so it is often used as a primer or adhesive rather than as a structure. In fact, their properties have been recognized, and their use in these fields is increasing year by year. Among them, ethylene vinyl acetate emulsion has recently been widely used to produce a stable emulsion with polyvinyl alcohol as a protective colloid, taking advantage of the fact that polyvinyl alcohol has an affinity with cement and gradually forms chemical bonds. ing. In other words, vinyl acetate emulsions containing polyvinyl alcohol as a protective colloid, especially ethylene-vinyl acetate emulsions, mix better with cement than other synthetic resin emulsions, increase water retention, and gradually form chemical bonds with cement. Because of its formation, it has a strong bonding force with concrete or mortar, and also exhibits a relatively strong bonding force with tiles and wall paints containing a large amount of inorganic fillers.
Therefore, we investigated various polyvinyl alcohols and found that by making the stabilizer polyvinyl alcohol cationic, the bonding force with concrete or mortar will further increase, and it will exhibit an extremely large bonding force with tiles and paints with many inorganic fillers. This led to the discovery of the present invention. An object of the present invention is to provide a cement mortar that has good workability and high adhesion to concrete, mortar, tile steel plates, inorganic filling materials, etc. That is, by mixing an emulsion of cationic polyvinyl alcohol with cement, it exhibits good properties unique to polyvinyl alcohol stabilizers, such as compressive strength, bending strength, weather resistance, abrasion resistance, impact strength, and adhesive strength. In particular, since it is cationic in terms of adhesive strength, the adhesive chemical bond strength to cement is significantly increased. This is because simply making the stabilizer cationic does not significantly increase the adhesive strength.
I think that having both cationic properties and the properties of polyvinyl alcohol is what gives it such excellent properties. That is, it is a cement composition prepared by kneading into cement an emulsion of vinyl acetate or vinyl acetate copolymer using modified polyvinyl alcohol containing a cationic group in the molecule as a stabilizer. The modified polyvinyl alcohol is obtained by completely or partially saponifying a copolymer of vinyl acetate and a polymerizable unsaturated compound that imparts cationic properties, and the degree of saponification is 60 to 100 mol%. say something Further, the degree of polymerization of the copolymer is in the range of 300 to 3000, which is effective as a protective colloid.
Also, what is the cationic polymerizable unsaturated compound that copolymerizes with vinyl acetate?

[Formula] (R ¹ , R ² , R ³ are H, or a low-molecular alkyl group or a phenyl group, R ⁴ is a lower alkyl group, and Y ^- is an anion). Specifically, 1-vinylimidazole, 1-vinyl-2-methylimidazole, 1-vinyl-2
- Quaternized salts of imidazole such as -ethylimidazole, 1-vinyl-2-phenylimidazole, 1-vinyl-2,3-dimethylimidazole, and 1-vinyl-2,4,5-trimethylimidazole. The copolymerization composition of these cationic unsaturated compounds is 0.01 to 10.0 mol%, preferably 0.2 to 10.0 mol%.
It is 6.0 mol%. If it is less than 0.01 mol%, the cationic property will be lost when it is made into an emulsion, and 10
If the amount exceeds mol%, it becomes difficult to produce a stable emulsion. Other modified products of these cationic polyvinyl alcohols such as etherification, esterification, and acetalization, or ethylene propylene, acrylamide, methyl methacrylate,
Fully or partially saponified polyvinyl alcohol partially copolymerized with vinylpyrrolidone or the like is also included. The emulsion obtained by polymerizing cationic polyvinyl alcohol as a stabilizer is an unsaturated compound that can be polymerized with a radical initiator, such as vinyl acetate, vinyl propionate, vinyl tertiary carboxylate (for example, VeoVa 10 from Ciel). ), vinyl esters such as vinyl stearate, ethylene,
α- such as propylene, isobutene, 1-hexane, etc.
Olefin, vinyl chloride, vinyl fluoride, halogenated unsaturated compounds such as vinylidene chloride, vinyl ethers such as lauryl vinyl ether and stearyl vinyl ether, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate , unsaturated organic acid esters such as ethyl methacrylate, dimethyl malonate, diethyl fumarate, butyl itaconate, styrene, butadiene, isoprene, chloroprene, acrylonitrile, methacrylonitrile, acrylamide, N-methylolacrylamide, allyl acetate, allyl sulfate , allyl alcohol, etc. This includes vinyl acetate emulsions, that is, vinyl acetate homopolymers and copolymers containing vinyl acetate as a main component and other copolymerizable unsaturated compounds. The term "copolymerizable unsaturated compound" as used herein includes all unsaturated compounds that can be polymerized by the above-mentioned radical initiator. The emulsion of the present invention using cationic polyvinyl alcohol as a stabilizer is not limited to those obtained by polymerization in the presence of cationic polyvinyl alcohol, but also includes those obtained by post-addition of cationic polyvinyl alcohol. In general, an emulsion of post-added polyvinyl alcohol has poor water resistance as a film, but when mixed with cement and used, its effect is almost unchanged and is effective. In addition, nonionic surfactants may be included in cationic emulsions, and anionic surfactants may also be used in small amounts. When vinyl acetate is polymerized in advance in the presence of cationic polyvinyl alcohol, the amount of polyvinyl alcohol used is 0.3 to 20 parts per 100 parts of monomer.
The amount is preferably 1 to 13 parts. Polymerization is initiated by addition of a water-soluble radical initiator. For example, hydrogen peroxide, persulfate, 2-azo-bis(2-methylpropamidinium) dihydrochloride 2-azo-bis-
(2'-isopropylimidazolinium) dibasic acid salts are used. Other sodium bisulfite,
A reducing agent such as sodium pyrosulfite, sodium metasulfite formaldehyde adduct, tartaric acid, and a salt such as sodium carbonate or sodium phosphate may coexist. Polymerization methods include starting polymerization with a nonionic surfactant or anionic surfactant and adding cationic polyvinyl alcohol midway through the polymerization, or starting polymerization with only cationic polyvinyl alcohol and adding cationic polyvinyl alcohol midway through. There are methods such as adding polyvinyl alcohol or adding a surfactant. Polymerization temperature is 30° to 100°C, preferably 40° to 90°C,
The pH during polymerization is preferably maintained at 3-8. The emulsions of the present invention are mostly cationic. The fact that the particles are cationic can be determined by observing electrophoresis measured using a zetameter, etc., and by observing that the particles move toward the cathode, and by measuring the electrophoretic velocity (mobility), it can be determined that the particles are cationic. (Zeta potential) can be calculated. In the present invention, it is essential for the stabilizer to be cationic and to be polyvinyl alcohol in order to improve the adhesion performance of the cement admixture. This is different from emulsions using other cationic protective colloids or surfactants. When the above-mentioned emulsion is kneaded into cement, it is used in a solid content ratio of 1 to 50% by weight, preferably 5 to 20% by weight, based on the cement. In addition, an appropriate amount of standard sand silica sand, calcium carbonate, gypsum, pozzolan, slag, and other inorganic fillers can also be used. EXAMPLES The present invention will be specifically explained below with reference to Examples, but these Examples are not intended to limit the present invention in any way. In addition, unless otherwise specified, all parts or percentages are based on weight. Example 1 2500 parts of vinyl acetate and methanol were placed in a reaction tank equipped with a stirrer, thermometer, dropping funnel, and reflux condenser.
1000 parts and 2.2 parts of 1-vinyl-2,3-dimethylimidazolinium chloride were placed in a constant temperature bath, and the system was purged with nitrogen while stirring, and then the internal temperature was raised to 60°C. 3.1 parts of 2,2'-azobisisobutyronitrile and 71 parts of methanol were added to this system to initiate polymerization. During the polymerization time of 2 hours and 20 minutes, 54 parts of a 25% methanol solution of 1-vinyl-2,3-dimethylimidazolinium chloride was added dropwise depending on the solid content concentration in the system. The solid content concentration in the system at the time of termination of polymerization was 39.5%. Vinyl acetate monomer remaining in the system was expelled by a conventional method. This copolymer was saponified to obtain a white modified PVA powder.
This modified PVA contained 0.4 mol% of 1-vinyl-2,3-dimethylimidazolinium chloride units, and the degree of saponification of vinyl acetate units was 80 mol%. The viscosity of this 4% aqueous solution of modified PVA at 20°C was 22.1 cp. Next, in a reaction tank equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, 80 parts of the modified PVA was dissolved in 950 parts of distilled water, and the pH was adjusted to 4.0 with 50% acetic acid aqueous solution while stirring. Subsequently, 200 parts of vinyl acetate monomer were added, the temperature was raised to 60°C, 6 parts of a 60% aqueous hydrogen peroxide solution was added, and the temperature was raised to 70°C. While maintaining this temperature, 800 parts of vinyl acetate was continuously added dropwise over 3 hours to carry out emulsion polymerization. 1.5 hours after the start of polymerization, 4 parts of hydrogen peroxide aqueous solution was added. After the dropwise addition of vinyl acetate was completed, the temperature was raised to 80°C, maintained for 30 minutes, cooled to room temperature, and the pH was adjusted to 6.0 with an aqueous ammonium solution. The cationic polyvinyl acetate emulsion thus obtained had a viscosity of 450 cp at 25°C at a resin concentration of 50%, excellent mechanical stability and dilution stability, and a zeta potential measured by a zeta meter of 25.9 mV. . This cationic emulsion with a solid content of 50% is used as Portland cement.
Add 30 parts to 100 parts of Toyoura standard sand, add 20 parts of water and knead, and after 20 minutes, mix the mortar board (40 x 40 mm) to a thickness of 3 mm, and immediately attached to a slate plate, ceramic plate, and steel plate. After curing under standard conditions (20° C., 65% RH) for 3 weeks, a measuring jig was set and the tensile speed was adjusted to 1 mm/min using an autograph to perform measurements. The results are shown in Table 1, and the adhesive performance is clearly improved compared to Comparison 1. Comparative Example 1 In Example 1, 20% of a 4% aqueous solution with a saponification degree of 88 mol%, which does not contain a modifying group, was used instead of the modified PVA.
Example 1 using PVA with a viscosity of 8.0 cp at °C
A polyvinyl acetate emulsion was produced in the same manner as above. The resulting emulsion has a resin content of 50%.
The Bruckfield viscosity at 25℃ is 80cp,
The zeta potential was -25.0 mV, indicating anionic properties. Regarding this emulsion, the adhesion of the mortar mixture was examined in the same manner as in Example 1. Table 1 shows the results.
Shown below.

【table】

Claims (1)

[Claims] 1. The following general formula (Here, R ¹ , R ² , R ³ are hydrogen, lower alkyl group, or phenyl group, R ⁴ is lower alkyl group, Y ^-
represent anions. ) A cement composition prepared by kneading with cement an emulsion containing modified polyvinyl alcohol as a stabilizer containing copolymerized units represented by: 2. The composition according to claim 1, wherein the emulsion is a vinyl acetate homopolymer emulsion or a copolymer emulsion of vinyl acetate and a polymerizable unsaturated compound. 3. The composition according to claim 2, wherein the polymerizable unsaturated compound is ethylene, vinyl ester, or acrylic ester. 4. The composition according to claim 2, wherein the emulsion is a cationic emulsion. 5. The composition according to claim 4, wherein the emulsion is an ethylene-vinyl acetate copolymer emulsion and the copolymer has an ethylene content of 20 to 60 mol%.