JPH01172250A - Retardant for cement - Google Patents

Abstract

PURPOSE:To produce retardant for cement having the effect improving tensile strength of concrete together with the retarding effect for cement hardening, by using polymer obtd. by emulsion polymerizing specified acrylic acid ester, ethylene and vinyl acetate, as main component. CONSTITUTION:The polymer is produced by emulsion polymerizing (A) acrylic acid ester of formula (where, R is C1-C5 alkyl group) (e.g. 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate), (B) ethylene and (C) vinyl acetate. The polymer is preferably copolymerized, so as to contain about 1-40wt.% component (A) and about 5-40wt.% component (B). The retardant for cement is constituted with the obtd. polymer as main component. The amt. of the retardant to be added to concrete, etc., is suitably about 2-20pts.wt. as solid content to 100pts. wt. cement.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cement admixture made of a polymer, and more particularly to a cement retarder.

<Prior art and its problems> In general, cement retarders are admixtures for cement that delay the setting and hardening of mortar and concrete by delaying the hydration reaction of cement.

Conventional retarders for cement include two types: inorganic and organic.
There are various types; for example, inorganic types include lead oxide, boron oxide,
Borax, zinc chloride, zinc oxide, magnesium silicate, etc., and in organic systems, sugar, alcohol, polyhydroxy compounds such as methyl cellulose, ethyl cellulose, polyvinyl alcohol, dextrin, and sodium polyacrylate, oxycarboxylate, Lignosulfonate, gluconate, etc. are used. The purpose of its use is to cope with the long transportation of ready-mixed concrete in the summer,
These include preventing cold joints in continuous pouring, eliminating nighttime work, integrating pouring joints, and alleviating temperature stress in larger concrete structures.

On the other hand, in order to improve the shortcomings such as tensile strength, drying shrinkage and chemical resistance caused by cement hydrate, ethylene-vinyl acetate copolymer emulsion (EVA) and acrylic ester copolymer emulsion are used for mortar and concrete. It is common practice to mix resin emulsions such as these or rubber latexes such as styrene-butadiene rubber (SBR), and recently polymer cements using these in combination have also been consumed in large quantities as general-purpose construction materials. .

<Means for Solving the Problems> The present inventor has focused on the increasing frequency of using cement retardants and polymers in combination, and has developed a method for adding cement polymers to cement polymers without impairing their inherent ability to improve the physical properties of mortar and concrete. As a result of intensive studies to solve the above-mentioned problems related to retarders for cement by imparting them with a function as a retarder, we discovered that the above-mentioned problems could be solved by using a specific monomer, and completed the present invention. did.

That is, the present invention has the general formula CI2=CHC00CHzC
fl□0R (R represents an alkyl group having 1 to 5 carbon atoms)
This is a retarder for cement whose main component is a polymer obtained by emulsion copolymerization of the compound represented by the above formula, ethylene, and vinyl acetate.

The present invention will be explained in detail below.

The general formula CI2=CHC00CHzCIIzOR (hereinafter referred to as general formula A) belongs to what is usually called an acrylic ester, and R is an alkyl group having 1 to 5 carbon atoms, and an alkyl group having 1 to 2 carbon atoms is particularly preferable.

Monomer represented by general formula A (hereinafter referred to as the present monomer)
Examples include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate and 2-butoxyethyl acrylate.

Most monomers that can be copolymerized with this monomer have a (CHz=CII) structure, including ethylene and vinyl acetate, but from the perspective of improving the physical properties of cement, copolymerization with ethylene-vinyl acetate can be used. It is preferable.

The co-IJ combination of the present monomer and ethylene-vinyl acetate will be explained below.

The ethylene content in the terpolymer emulsion (hereinafter referred to as the present emulsion) consisting of ethylene-vinyl acetate and the present monomer is preferably 5 to 40% by weight. If the ethylene content is less than 5% by weight, the vinyl acetate in the emulsion will be easily hydrolyzed by alkali when mixed into cement, which is not preferable. On the other hand, if it exceeds 40% by weight, a stable emulsion cannot be obtained.

Furthermore, the content of the present monomer in the present emulsion is preferably 1 to 40% by weight. If it is less than 1% by weight, the retarding effect on cement will not be sufficient, while if it exceeds 40% by weight, the miscibility with cement may deteriorate.

There are no particular limitations on the method for producing the emulsion of the present invention, and any known emulsion polymerization method can be used. However, since the aforementioned monomer has high reactivity, it is better to add it continuously during the polymerization to achieve uniform copolymerization.

When the entire amount of this monomer is charged into a polymerization reactor and the reaction is started,
A homopolymer of this monomer is likely to be formed, which may result in poor miscibility with cement.

There are no particular restrictions on the polymerization conditions, but - for boat fishing, the polymerization temperature is 2.
0~80℃, polymerization pressure 10~90kg/cn! is used. Examples of emulsifiers include polyvinyl alcohol, protective colloids such as methyl cellulose and hydroxyethyl cellulose, nonionic surfactants such as polyoxyethylene condensates and polyoxyethylene polyoxypropylene block copolymers, and alkylbenzene sulfonates and lauryl sulfate salts. Examples include anionic surfactants. These can be used alone or in combination of two or more.

Examples of the catalyst include persulfates such as potassium persulfate, hydrogen peroxide, and various organic peroxides.

In the case of a redox initiation system, a reducing substance such as formaldehyde sodium sulfoxylate is further used in combination.

Furthermore, if necessary, known additives such as a pH 1jJ adjuster (buffer), an antifoaming agent, and a preservative can be used.

The solid content in this emulsion is adjusted by the amount of monomers to be copolymerized and water, but is preferably 40 to 65% by weight from an industrial standpoint.

The amount of the present emulsion obtained by the above method added to mortar or concrete is preferably 2 to 20 parts by weight in terms of solid content per 100 parts by weight of cement, and less than 2 parts by weight.
The effect of improving the physical properties of mortar and concrete and the effect of retarding the hydration reaction are insufficient, and on the other hand, if the amount exceeds 20% by weight, the miscibility with cement may deteriorate.

The emulsion obtained in the present invention may contain known cement polymers such as SBR and polyacrylate, AE agents,
It can be used in combination with cement admixtures such as water reducers, fluidizers, shrinkage regulators, rust preventives, waterproofing agents, and antifreeze agents.

<Example> The present invention will be further explained below with reference to Examples.

Example 1 The following raw materials were charged into a stainless steel autoclave equipped with an electromagnetic stirrer and having an internal volume of 101 cm.

Pure water 2.650 g Vinyl acetate 2.280 g xypropylene block copolymer) Hydroxyethyl 45 g (manufactured by Fuji Chemical Cellulose Co., Ltd.) Hitenol N-17J 22.5 g (polyoxyalkyl (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) or allyl) sulfate ammonium salt Sodium acetate 12g The internal temperature was raised to 70°C and ethylene was introduced to 50kg/cal. Ammonium persulfate was added as a catalyst.
6 g was added to start polymerization. The temperature of the indoor bath was kept constant by adjusting the jacket.

In addition, as this monomer, 2-methoxyethyl acrylate (Toagosei Chemical Industry type, trade name [Acrylate C-IJ
570 g was uniformly and continuously added in portions over 8 hours from the start of polymerization.

After 10 hours, the cooled contents were removed.

The content is a stable emulsion with few coarse particles, solid content 52
．． 5% by weight, viscosity 3.700 cps, and its polymer composition was 66% by weight vinyl acetate units, 17% by weight ethylene units, and 17% by weight 2-methoxyethyl acrylate units. (referred to as Polymer A) Polymer A and Polymer A (produced in the same manner) except that 2-butoxyethyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd.) with 4 carbon atoms was used instead of 2-methoxyethyl acrylate as a monomer. .

The resulting emulsion was stable, with a solid content of 52.1% by weight and a viscosity of 3.900 cps, and its polymer composition was vinyl acetate uni, 5% by weight of Toro, 16% by weight of ethylene units, and 19% by weight of 2-butoxyethyl acrylate units. Met. (referred to as Polymer B) Using the materials shown below, formulations were prepared in the proportions shown in the table. The preparation method was in accordance with "How to make polymer cement mortar in JisAl 171r test laboratory".

(1) Cement Ordinary Portland cement (2
) Aggregate Toyoura standard sand (3) Polymer A: 2-methoxyethyl acrylate is used as the main monomer. Polymer B: 2-butoxyethyl acrylate is used as the main monomer. , viscosity 4, 800 cps, composition: ethylene/vinyl acetate = 20/80'') The physical properties were measured by the following method.

(1) Mortar physical properties Compliant with JIS A6203 "Polymer dispersion for cement mixing" except that the amount of polymer added was changed.

(2) Effect of retardant 1 kg of (polymer) cement mortar was placed in a PVC container wrapped with styrofoam to provide insulation, and a thermosensor was inserted into the container to suppress the heat generated by the hydration reaction. Conditions were recorded over time as a temperature difference (ΔT) from room temperature.

(3) When mixed mortar is mixed with a mortar mixer,
Cases in which kneading was difficult without applying considerable force were rated as "poor," and other cases were rated as "good."

It was found that the effect of improving the physical properties of the mortar and the effect of retarding the hardening with cement were observed, and it was also found that the degree of hardening retardation differed depending on the amount of polymer added.

<Effects of the Invention> According to the present invention, it is possible to obtain a polymer for mixing in cement that has both the effect of improving the physical properties of mortar and concrete and the effect of retarding hardening.

Patent applicant Denki Kagaku Kogyo Co., Ltd. Procedural amendment (voluntary) February 19, 1985 Director General of the Patent Office Kunio Ogawa 1, Indication of the case 1988 Patent Application No. 329637 2, Name of the invention Delay for cement Agent 6. Relationship with the person making the amendment Patent applicant address ■100 1-4-1 Yurakucho, Chiyoda-ku, Tokyo
Column 5 of detailed explanation of the invention in the specification of No. 5, contents of amendment 5-1. The 12th statement of the specification is amended as shown in the attached sheet.

Claims (1)

[Claims] General formula CH_2=CH=-COOCH_2CH_2OR
(R represents an alkyl group having 1 to 5 carbon atoms), a cement retarder whose main component is a polymer obtained by emulsion copolymerization of ethylene and vinyl acetate.