JPH0146469B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cement composition with improved workability and excellent adhesion. That is, a special aqueous dispersion of vinyl acetate-(meth)acrylate-ethylene copolymer with polyvinyl alcohol as a protective colloid (hereinafter referred to as
The present invention relates to a composition that does not harden rapidly during construction work by blending VAAE dispersion (VAAE dispersion) and cement, has excellent workability, and provides excellent adhesion after hardening. When a polymer aqueous dispersion is mixed with cement,
It has low water permeability and high impact strength, tensile strength, bending strength, and adhesive strength. In particular, when using these cements as fillers or primers, it is important that they adhere to various types of mortar and concrete and have good weather resistance. Aqueous polymer dispersions are superior. (French Patent No. 1455910 (1966)) However, when preparing an aqueous vinyl acetate-ethylene copolymer dispersion, it is important to use polyvinyl alcohol as a protective colloid. Aqueous dispersions of vinyl-ethylene copolymers lack these characteristics. (Tokukai Akira
49-97818) Therefore, the aqueous dispersion commonly used for mixing cement uses polyvinyl alcohol as a protective colloid. The characteristics of such an aqueous dispersion are that it is easily compatible with cement, has a strong bonding force due to chemical reaction, has good dispersibility, has no migration of the resin after drying, and has excellent water retention. Furthermore, compared to surfactant-based materials, there is less foaming, so compressive strength and bending strength are increased, and water permeation resistance does not decrease. Since it is most important to use polyvinyl alcohol as a protective colloid, it is possible that an aqueous polyvinyl acetate dispersion would be optimal, but this is easily saponified by alkali and the water resistance of the resin itself is significantly reduced. As a result, the characteristics of resin miscibility are lost. Therefore, an aqueous vinyl acetate-ethylene copolymer dispersion with excellent alkali resistance is suitable, but in order to further improve the alkali resistance, we investigated the introduction of (meth)acrylic acid ester. As a result, when an aqueous dispersion of vinyl acetate-ethylene copolymer was first made and then polymerized by addition of (meth)acrylic acid ester, when the aqueous dispersion was mixed with cement, polyvinyl alcohol was used as a protective colloid. It has been found that the deterioration in workability due to mixing with cement, which is a drawback of aqueous vinyl acetate-ethylene copolymer dispersions, can be prevented. Workability means that when cement and aqueous dispersion are mixed, they are evenly dispersed, the flow of the cement mixture is large despite the small amount of water used, and there is no sudden decrease in flow value during work. Say something. In other words, as seen in JP-A No. 49-97818, a composition of an aqueous dispersion of vinyl acetate ethylene copolymer containing polyvinyl alcohol as a protective colloid and cement is extremely excellent as a filler or splicing agent for cement or mortar. However, it has the disadvantage that the cement composition hardens quickly after mixing, reduces fluidity during application or spraying, and reduces workability. Therefore, as a countermeasure to this problem, other substances such as surfactants are often mixed, but in this case, although the fluidity is improved, the adhesion is reduced. However, the composition of the present invention has well-balanced performance as a cement mixture, with excellent fluidity and workability, and excellent adhesion performance. That is, ethylene/vinyl acetate/( This is a cement composition with excellent workability and adhesion, which is made by mixing 1.5 to 30 parts by weight of an aqueous meth)acrylate copolymer dispersion as a resin solid content with respect to 100 parts by weight of cement. The method for producing the aqueous dispersion in the present invention is as follows. 2.5 to 10 parts by weight of polyvinyl alcohol (100 parts by weight of resin)
The (meth)acrylic ester and vinyl acetate were added to an aqueous vinyl acetate-ethylene copolymer dispersion prepared by copolymerizing 70 to 90 parts by weight of vinyl acetate and 10 to 30 parts by weight of ethylene (based on parts by weight) as a protective colloid. meth)acrylic acid ester is 50% lower than vinyl acetate.
% or more (meth)acrylic acid ester is added all at once or sequentially depending on the case, polymerized with an anionic aqueous radical initiator, and by controlling the residual monomer to 1% or less, stable aqueous dispersion is achieved. Get the liquid. The polyvinyl alcohol used in this production method is one obtained by saponifying polyvinyl acetate by 80 to 100% and has an average degree of polymerization of 100 to 4,000. This polyvinyl alcohol also includes modified products into which carboxylic acid groups, sulfonic acid groups, and cationic groups have been introduced. Also, vinyl acetate-ethylene copolymer aqueous dispersion (composition ratio 70-90/30-10) can be made by various methods, but when vinyl acetate is charged all at once, the ethylene pressure is 15
It is obtained by polymerizing at ~60Kg/ ^cm2 , but it goes without saying that the ethylene content, particle size, viscosity, stability, etc. are affected by the size of the polymerization tank, stirring method, type of initiator, polymerization time, etc. stomach. In addition, polymerization is often carried out by sequentially adding vinyl acetate monomers, and products made by this method are also effective. In addition, as the composition of this vinyl acetate ethylene copolymer aqueous dispersion, (meth)acrylic acid ester (the ester group is an aliphatic alcohol ester having 1 to 10 carbon atoms) is used.
Those containing 10% by weight or less are also effective. Next, when (meth)acrylic acid ester is added, it may be done after the polymerization is temporarily stopped and ethylene is completely removed, or addition may be started when the ethylene pressure decreases without stopping the polymerization. However, if the ethylene pressure is too high, polymerization may not proceed smoothly, so it is desirable to keep it below 5 kg/cm if possible. It is also effective to add a portion of polyvinyl alcohol, which is effective as a mortar composition, before adding the (meth)acrylic acid ester. The ester group of the (meth)acrylic ester added later is an ester of an aliphatic alcohol having 1 to 10 carbon atoms. For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate. Esters etc. In addition to the (meth)acrylic acid ester added in the latter half of the polymerization, it is also possible to copolymerize vinyl compounds, such as vinyl acetate, vinyl propionate, vinyl versatate, maleic acid ester, fumaric acid ester, styrene, alkyl vinyl ether, Acrylonitrile, acrylamide, etc. It is also possible to copolymerize di(meth)acrylic acid ester. It is necessary to use an anionic aqueous radical initiator as the radical initiator used in the post-addition polymerization of the (meth)acrylic ester. This is because if an initiator other than this is used, the flow will be reduced. Anionic aqueous radical initiators are those that generate radical fragments containing anionic groups upon decomposition, and easily ionically dissociate from peroxide or redox reducing agents. Examples include persulfate, hydrogen peroxide-sodium sulfite, hydrogen peroxide-Rongalite, hydrogen peroxide-sodium nitrite, hydrogen peroxide-tartaric acid, and the like. The amount of the VAAE aqueous dispersion added to the cement is 1.5 to 30 parts by weight based on 100 parts by weight of cement as solid content of the VAAE emulsion aqueous dispersion. If it is less than 1.5 parts by weight, the adhesion of mortar will decrease, and if it is more than 30 parts by weight, workability will decrease.
This is undesirable because it takes a long time to harden until adhesion develops, and the flexibility increases, making it impossible to obtain the strength and rigidity inherent in cement. Moreover, from an economic point of view, it is no longer meaningful to mix the aqueous dispersion any further. In reality, inorganic fillers are often mixed in with cement. As the inorganic filler, river sand, sea sand, silica sand, etc. are mainly used. In particular, when used in a cement-sand-VAAE resin formulation where the proportion of sand is small, the effect of improving the flow value is particularly remarkable. Next, the present invention will be specifically explained with reference to Examples. Note that "parts" indicate "parts by weight." Example 1 Polyvinyl alcohol with a degree of saponification of 87% and an average degree of polymerization of 500 in a 5-autoclave with a 500 rpm stirrer
70g, vinyl acetate 980g, Rongarit 14.5g, iron chloride 0.03g and pure water 1460g were charged, the temperature was raised to 50℃, the ethylene pressure was increased to 50Kg/ ^cm2 , hydrogen peroxide was added, and after 3 hours, the remaining vinyl acetate was dissolved. When the amount of ethylene decreased to less than 10% of the total, ethylene injection was stopped, and ethylene was released to reduce the amount to 20 kg/ ^cm2 . After that, polymerization was continued for another 2 hours, and ethylene was purged for a long time.
Kg/ ^cm2 or less. Then 244g of methacrylic acid methyl ester and 61g of acrylic acid butyl ester
was added over 2 hours with hydrogen peroxide,
After the addition was complete, polymerization was continued for an additional hour and VAAE
An aqueous dispersion (solid content 50.5%) was obtained. This VAAE
10 parts as solid content, 100 parts of cement, 300 parts of standard sand
1 part, and 62 parts of water. The flow value immediately after blending is
The flow value after 120 minutes was 157, which was good. The adhesion performance was also good. (See Table 1) Example 2 Using the aqueous dispersion of VAAE in Example 1, the solid content was 5 parts, 100 parts of cement, and standard sand.
The flow value immediately after mixing 300 parts and 65 parts of water was 177, and the flow value after 120 minutes was 152. Example 3 Using the aqueous dispersion of VAAE in Example 1, the solid content was 25 parts, cement was 100 parts, and standard sand was added.
The flow value immediately after mixing 300 parts and 45 parts of water was 160, and the flow value after 120 minutes was 145. Example 4 In Example 1, 244 g of methacrylic acid methyl ester and 61 g of acrylic acid butyl ester were added sequentially, and during polymerization, ammonium persulfate was added and polymerized, and after 3 hours, a VAAE aqueous dispersion (solid content 49.8%) was prepared. ) was obtained. This VAAE as solid content
The flow value of a mixture of 10 parts, 100 parts of cement, 300 parts of standard sand, and 62 parts of water was 187, and the flow value after 120 minutes was 169, which was extremely good. Example 5 5 In an autoclave, 70 g of polyvinyl alcohol with a degree of saponification of 87% and an average degree of polymerization of 500, 980 g of vinyl acetate, 14.5 g of Rongarit, 0.03 g of iron chloride,
After charging 1340 g of pure water and raising the temperature to 50° C., the ethylene pressure was increased to 30 Kg/cm ² and hydrogen peroxide was added to start polymerization. After 2.5 hours, when the residual vinyl acetate was less than 10%, the injection of ethylene was stopped and polymerization was continued for 2 hours. When the vinyl acetate monomer was less than 1%, the ethylene pressure was lowered to 2 kg/cm ² and vinyl acetate was added. Polymerization was carried out by continuously adding 125 g and 56 g of butyl acrylate for 2 hours. Meanwhile, hydrogen peroxide was continuously added as a polymerization initiator. After the addition of the monomer was completed, the polymerization was continued for another 2 hours, and then stirring was stopped, the temperature was lowered, and the resulting VAAE aqueous dispersion (solid content 50.6%) was taken out. 10 parts of this VAAE as solid content, 100 parts of cement, 300 parts of standard sand
% and 62 parts of water, the flow value was good. Example 6 5 In an autoclave, 70 g of polyvinyl alcohol with a degree of saponification of 87% and an average degree of polymerization of 500, 980 g of vinyl acetate, and 14.5 g of Rongalit were placed in 1655 g of pure water, and after raising the temperature to 50°C, the ethylene pressure was increased to 50 Kg/cm. ²
Hydrogen peroxide was added to start polymerization.
After 2.5 hours, when the remaining monomer was below 10%, ethylene injection was stopped and polymerization was continued for another 2 hours. When the vinyl acetate monomer was below 1%, an antifoaming agent was added and the ethylene pressure was increased to 2 kg/cm ²
It was lowered to. Polymerization was carried out for 2 hours while adding a mixed solution of 120 g of vinyl acetate, 300 g of methyl methacrylate, and 100 g of 2-ethylhexyl acrylate and potassium persulfate. After the addition, polymerization was further carried out for 2 hours to obtain a VAAE aqueous dispersion. 10 parts of this VAAE as solid content, 100 parts of cement, 300 parts of standard sand,
The flow value of the mixture containing 62 parts of water was 174 immediately after mixing.
After 120 minutes it was 153. Comparative Example 1 87g of polyvinyl alcohol with saponification degree of 87% and average degree of polymerization of 500 in autoclave, vinyl acetate
Prepare 1220g, Rongarit 9g, pure water 950g,
Raise the temperature to 50℃ and polymerize at an ethylene pressure of 50Kg/ ^cm2 ,
A vinyl acetate-ethylene copolymer aqueous dispersion (solid content 50%, ethylene content 21%) was obtained. A mixture of 10 parts of this vinyl acetate-ethylene copolymer aqueous dispersion as a solid content, 100 parts of cement, 300 parts of standard sand, and 62 parts of water had a flow value of 155 immediately after mixing, and a flow value after 120 minutes. It was 105. Comparative Example 2 In Example 1, t-butyl hydroperoxide was added as an initiator before adding 244 g of methacrylic acid methyl ester and acrylic acid butyl ester in the latter half of the polymerization, and the polymerization was completed in about 4 hours and stabilized. Aqueous dispersion of VAAE (solids content 55.2
%) was obtained. When this VAAE aqueous dispersion was mixed with 10 parts of solid content, 100 parts of cement, 300 parts of standard sand, and 62 parts of water, the flow value immediately after mixing was 151, but it became 95 after 60 minutes. Comparative Example 3 In an autoclave with a 500 rpm stirrer, 55 g of polyoxyethylene nonyl phenyl ether (40 polyoxyethylene units), vinyl acetate
950g (2/3 added sequentially) Rongarit 14.5
g, pure water 1090g, ethylene pressure 50Kg/cm ²
244 g of methyl methacrylate and 61 g of butyl acrylate to 2430 g of vinyl acetate-ethylene copolymer aqueous dispersion (copolymerization composition 81:19) polymerized by adding potassium persulfate aqueous solution.
was added over 2 hours using potassium persulfate as an initiator, followed by further polymerization for 1 hour to obtain a VAAE aqueous dispersion (solid content 54.1%). When 10 parts of VAAE aqueous dispersion as a solid content, 100 parts of cement, 300 parts of standard sand, and 62 parts of water are mixed, the flow value immediately after mixing is 177, and after 120 minutes it is 160.
However, the adhesion performance was extremely poor.

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Claims (1)

[Claims] 1 Ethylene/vinyl acetate/(meth)acrylic acid ester obtained by copolymerizing (meth)acrylic acid ester with an anionic aqueous radical initiator in the presence of an aqueous dispersion in which ethylene and vinyl acetate are copolymerized using polyvinyl alcohol as a protective colloid. ) Cement acrylate copolymer aqueous dispersion
A cement composition with excellent workability and adhesion, which is made by mixing 1.5 to 30 parts by weight of resin solids per 100 parts by weight.