JPH0261431B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rust preventive agent for mortar or concrete, and its purpose is to develop a rust preventive agent that exhibits excellent rust preventive properties even in environments containing salt. Traditionally, mountain sand and river sand have been used as fine aggregates for mortar and concrete, but due to the construction boom in recent years, these sands have become scarce, and sea sand, which has a large amount of salt attached, is being used instead. I've come to feel like I'm being treated like that. However, a serious problem arises in that the steel frames and reinforcing bars that are buried in mortar or concrete are subject to corrosion. As a countermeasure to this problem, there is a method of washing the sea sand with water, but it is not very effective despite the complicated operation. For this reason, when using sea sand, it is practically necessary to use a rust preventive agent, and nitrites and dichromates are known, but the former is highly toxic and causes pollution problems, and is not used. The disadvantage is that the amount is large, and as is well known, the latter is designated as a hazardous substance by the Prime Minister's Office Ordinance, and there are major problems with its use. For the above reasons, there is currently a strong demand for an excellent rust preventive agent that has a good rust preventive effect and is free from toxicity and pollution problems. As a result of intensive research in order to meet the above-mentioned needs, the inventors of the present invention have discovered that the desired purpose can be achieved when an acid hydrazide polymer having the specific structure shown below is used as an active ingredient of a rust preventive agent. , finally completed the present invention. That is, the present invention has the following general formula (In the formula, X is a hydrogen atom or a carboxyl group, Y
is a hydrogen atom or a methyl group, A is an acrylamide unit, methacrylamide unit, acrylic ester unit, methacrylic ester unit, or maleic anhydride unit, and B is acrylamide, methacrylamide, acrylic ester, methacrylic ester, or maleic anhydride. Indicates other monomer units copolymerizable with the acid, and l, m, and n have the following relationships: 3 mol%≦≦100 mol%, 0 mol%≦m+n≦97 mol%, l+m+n=100 mol%) The present invention relates to a rust preventive agent for mortar or concrete containing a water-soluble polymer compound having an acid hydrazide group. The rust preventive agent of the present invention has very low toxicity and exhibits excellent rust preventive power even when used in small amounts. Furthermore, it can be used in combination with common admixtures for concrete such as oxycarboxylate, triethanolamine, lignin sulfonate, etc., and it does not have a negative effect on the performance of each, but rather shows a synergistic effect. . In the acid hydrazide polymer of the present invention, as the acrylic acid and methacrylic ester providing the monomer unit (A), lower alkyl esters are usually used, and more specifically, methyl (meth)acrylate, methyl (meth)acrylate, etc. ) Ethyl acrylate, (meth)
Examples include butyl acrylate and ethylhexyl (meth)acrylate. Preferred examples of the monomer providing the monomer unit (B) include vinyl chloride, vinylidene chloride, vinyl acetate, butadiene, styrene, and acrylonitrile. Furthermore, in the acid hydrazide polymer used in the present invention, the content of acid hydrazide groups is 3 mol%.
It is necessary that it is above. If the content of acid hydrazide groups is less than 3 mol %, the antirust effect will be weakened, which is not preferable. The acid hydrazide polymer used in the present invention has a molecular weight of 500 or more and 10,000,000 or less, preferably 10-2,000,000. It is difficult to synthesize those with a molecular weight of less than 500, and
If it exceeds 1,000,000, the ability to coagulate concrete becomes stronger, which is not preferable. The acid hydrazide polymer used in the present invention is usually a homopolymer or copolymer of acrylamide, methacrylamide, acrylic ester, or maleic anhydride, or a copolymer of a monomer copolymerizable with these monomers. It can be obtained by In particular, the rust preventive agent of the present invention is effective for mortar or concrete that contains salt such as sea sand, and when the rust preventive agent of the present invention is used for mortar or concrete that contains salt, it is necessary to 0.01 per chloride (sodium chloride equivalent)
~10 times by weight, preferably 0.1 to 5.0 times by weight.
If the amount is less than 0.01 times the weight, the rust prevention effect is insufficient, and even if it is used in an amount greater than 10 times the weight, no further effect can be expected. The method of using the rust preventive agent of the present invention is not particularly limited, but for example, a method of dissolving it in mortar or mixing water used for preparing concrete, a method of mixing it in advance together with cement or aggregate, etc.
Examples include a method of adding it when preparing mortar or concrete. The rust preventive agent of the present invention has a wide range of applications, not only when sea sand with a high salt content is used, but also when mixing water with a high salt content, or when adding chloride as a hardening accelerator to mortar or concrete. If it contains salt, it can also be used as a rust preventive agent for metals such as steel frames and reinforcing bars. The present invention will be explained below by giving examples. Example 1 An aqueous solution containing 0.1% by weight of calcium hydroxide and 1% by weight of sodium chloride and having a pH of 12 was prepared and used as corrosive water. Pour 150 ml of corrosive water into a 200 ml glass beaker, add the rust preventive agent of the present invention shown in Table 1 below to a concentration of 1% by weight, and after dissolving it, test piece [JIS G 3108 (General steel material for polished steel bars) ) of SGD3
The material was made of the material specified in (1), the surface area was 25 cm ² , and the upper end suspension hole was φ5 m/m] and was hung at 30° C. for 15 days. Comparative Example 1 In place of the rust preventive of the present invention, calcium nitrite was added to
The same procedure as in Example 1 was carried out except that the amount was added in an amount of % by weight. Comparative Example 2 The same procedure as in Example 1 was carried out, except that 1% by mole of acrylic acid hydrazide groups, 99% by mole of acrylamide, and 1% by weight of a water-soluble polymer having acid hydrazide groups with a molecular weight of 100,000 were added. Ta. Comparative Example 3 The same procedure as in Example 1 was carried out except that the rust preventive of the present invention was not added. In Example 1 and Comparative Examples 1 to 3, the amount of corrosion (mg/dm ²・day,
(abbreviated as mdd) was measured. The results are shown in Table 1. mdd = weight of test piece before test (mg) - weight of test piece after test (mg) / surface area of test piece (dm ² ) x number of test days (
day）

[Table] As is clear from Table 1, the rust preventive performance of the rust preventive agent of the present invention is very excellent. Example 2 30 mol% acrylic acid hydrazide group, acrylic acid
The procedure was carried out in the same manner as in Example 1, except that the water-soluble polymers of the present invention expressed as 70 mol% and having a molecular weight of 1,000, 10,000, 100,000, and 1,000,000 were added to separate containers at a concentration of 0.5% by weight. Ta. Comparative Example 4 Calcium nitrite was used instead of the rust preventive of the present invention.
The same procedure as in Example 2 was carried out except that the amount was added to be 0.5% by weight. Table 2 shows the amount of corrosion (mdd) obtained in Example 2 and Comparative Example 4.

[Table] Example 3 The same procedure as in Example 1 was carried out except that the constituent units and addition amounts of the product of the present invention as shown in Table 3 were used. Comparative Example 5 Instead of the rust inhibitor of the present invention, 50 mol% of acrylic acid hydrazide groups, 40 mol% of acrylamide, 10 mol% of acrylic acid, and 0.005% by weight of the rust inhibitor of the present invention with a molecular weight of 10,000 were used. The same procedure as in Example 3 was carried out except for the addition. Comparative Example 6 Calcium nitrite 0.1 in place of the rust preventive of the present invention
The same procedure as in Example 3 was carried out except that % by weight was added. Table 3 shows the amount of corrosion (mdd) obtained in Example 3 and Comparative Examples 5 and 6. The above-mentioned Comparative Examples 1 and 4 are also shown.

【table】

[Table] As is clear from Table 3, the rust preventive performance of the rust preventive agent of the present invention is very excellent. Example 4 Ordinary Portland cement [Onoda Cement Co., Ltd.]
[Made] 305Kg/m ³ , Gravel (from Yoshinogawa) 1024Kg/m ³ ,
Sand [from Naruto, salt content 0.3% (sodium chloride equivalent)] 790 Kg/m ³ and approximately 204 Kg/m ³ of water were added and kneaded to give a slump of 20±1 cm. During mixing, the rust preventive agent of the present invention and other additives as shown in Table 4 are added, and the mixed concrete is coated with 600 g
Reinforcing bars polished with abrasive paper [JIS G 3123 (Polished steel bars) with material specified in SGD3 of JIS G 3108 (General steel materials for polished steel bars), 10mmφ, length 25
cm] was injected into a form frame (10 cmφ x 30 cm). This molded body was left outdoors, and after two years had passed, the molded body was destroyed and the state of rust on the reinforcing bars was observed. Comparative Example 7 The same procedure as in Example 4 was carried out except that sodium nitrite was added in an amount of 1 times the weight of the salts instead of the rust preventive of the present invention. Comparative Example 8 The same procedure as in Example 4 was conducted except that sodium ligninsulfonate was added in an amount of 1 times the weight of the salts instead of the rust preventive agent of the present invention. Comparative Example 9 The same procedure as in Example 4 was carried out except that sodium gluconate was added in an amount of 1 times the weight of the salt instead of the rust preventive of the present invention. Comparative Example 10 The same procedure as in Example 4 was carried out except that the product of the present invention was not added. In Example 4 and Comparative Examples 7 to 10, the results of observing the rusting state of the reinforcing bars after two years are shown in Table 4 based on the following criteria. ◎; Completely rust-proof 〇; 1-25% rust △; 25-50% rust ×; 50-100% rust

[Table] As is clear from Table 4, the antirust performance of the product of the present invention is very excellent, and it is easy to see that it is effective even when the amount added is small. Moreover, when used in combination with an admixture, no adverse effects are observed, and even a synergistic effect is observed.

Claims (1)

[Claims] 1. The following general formula (In the formula, X is a hydrogen atom or a carboxyl group, Y
is a hydrogen atom or a methyl group, A is an acrylamide unit, methacrylamide unit, acrylic ester unit, methacrylic ester unit, or maleic anhydride unit, and B is acrylamide, methacrylamide, acrylic ester, methacrylic ester, or maleic anhydride. Indicates other monomer units copolymerizable with the acid, where l, m and n have the following relationships: 3 mol%≦≦100 mol%, 0 mol%≦m+n≦97 mol%, l+m+n=100 mol%) A rust preventive agent for mortar or concrete containing a water-soluble polymer compound having a hydrazide group.