JPS5838378B2 - Polymer-cement blend composition for steel structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polymer cement admixture for the corrosion protection coating of steel structures.

Generally, cement mortar lining has been conventionally used as a corrosion-resistant coating method for steel materials.

However, this coating has drawbacks such as easy cracking, poor chemical resistance, and poor adhesion to steel materials.

In order to improve these problems, resin mortars (those that use resin as a binder to fix aggregates) and polymer cements, which are made by mixing so-called water-dispersed polymers in the form of latex or emulsions with cement mortar, have been developed. I came.

This type of polymer-cement blend composition has a polymer blended in it that not only increases the bonding strength of the hardened cement but also improves the adhesion to the object to be painted, and has excellent properties as a structural material and corrosion resistance. In order to be considered valid,
It is used in paving materials, waterproofing materials, chemical-resistant coatings, ship deck coverings, vehicle interior linings, etc.

Properties for these applications include adhesion to the substrate, abrasion resistance, waterproof effect, weather resistance, crack prevention, impact resistance, chemical resistance, elasticity, and especially corrosion resistance when the object to be coated is steel. Although the current polymer cements generally satisfy many of these requirements, there are still problems with corrosion resistance and other issues.

That is, (1) Most of the polymer cements used are water-dispersed polymers in the form of latex or emulsion, and those mixed with hydraulic cement, aggregate, etc. This causes rapid rusting.

This kind of rapid rusting is called flash rust, and it has been confirmed through experiments that it occurs in most polymer cements.

However, when there is flash rust, if a corrosive environment is encountered, the polymer cement coating may peel off from the steel surface, in combination with the volumetric expansion of the rust (flash rust) on the steel surface.

This is because the corrosion resistance of the emulsions, latex, etc. that are mixed into conventional polymer cements has not been considered.

On the other hand, it is believed that the alkali in cement stabilizes the steel, but in order to do so, it is necessary to maintain a pH of 12 or higher on the steel surface, and even though it is alkaline, the anti-corrosion effect of polymer cement is overestimated. It is dangerous to do so.

That is, FIG. 1 shows W. Wh iteman and R. This figure shows the relationship between PI{ and corrosion in steel, which was researched by Russell Russell, and it can be seen that when the pH is less than 12, corrosion increases rapidly.

In addition, 100 g of each of the aggregates and cements of Samples A61 to 7 shown in Table 1 were stirred and mixed with 900 cc of tap water, and then a polished mild steel material was suspended in the stationary liquid, and the change in pH of the liquid was measured by P.
The results of measurement with an H meter and observation of the state of rust are as shown in Table 1 and Figure 2. In the case of tap water (blank), slag, and sand, the pH is low and the rust is large, but In the case of Voltland cement and blast furnace cement, the average pH is high < (12 or more) and there is no rusting, while in the case of cement + slag and cement + silica sand, the PH is slightly lower and a small amount of rusting occurs on the test piece. There was found.

As mentioned above, when using polymer cement for corrosion protection, it is also necessary to consider the corrosion protection performance of the cement mixture.

(2) When lining or coating with conventional polymer cement, different types are designed for undercoating, intermediate coating, and topcoating, and the coating process requires multiple layers of coating. The number of construction days required was determined accordingly.

On the other hand, if you try to finish the desired thickness at once by omitting the process of overcoating, the disadvantage is that the coating will sag when spray finishing (5 to 8 coats) and cracks will occur in the cured coating. was there.

(3) Although it is said to be a corrosion-resistant material, the surface treatment and anti-corrosion treatment processes are not sufficiently considered, so in a corrosive environment (for example, exposed on the beach or in a place subject to wet and dry alternation), the steel surface will deteriorate in a very short period of time. Rust occurs at the interface between the coating material and the coating material, causing a decrease in adhesion.

(4) Furthermore, microscopic observation revealed that there were many void spaces inside the coating, and the coating lacked toughness.

The present invention eliminates the drawbacks of the above conventional polymer cements,
In addition to suppressing flash last, paintability and
The object of the present invention is to provide a polymer-cement mixture for steel structures that has improved adhesion and anti-corrosion effects.

The polymer cement blend composition of the present invention contains a rust preventive agent and a filler as one of the raw material components constituting the polymer cement, thereby increasing the rust prevention performance, which has been insufficiently addressed in the past. It enables a one-coat spray finish using the same material, and improves paintability, adhesion, etc.

The details will be explained below. The rust preventive agent added to polymer cement suppresses flash rust and improves the anticorrosion effect, but it is stable in an alkaline environment and is stable when mixed with polymers. It must be sufficiently effective in inhibiting rust.

The present inventors conducted experiments to suppress the flash rust of mixtures of various polymers and rust inhibitors, and found suitable combinations of polymers and rust inhibitors.

At this time, regarding the amount of rust preventive added to the water-dispersed polymer, based on the idea that the influence of the polymer on the occurrence of flash rust in the polymer cement structure is significant, based on the water-dispersed polymer, A quantitative study of the rust inhibitor was added to the solid content.

The experimental results are shown in Table 2. The six types of polymers shown in Table 2 were used as the test polymers, and the test rust preventives were nitrite-based (1), metaboric acid-based (2), and metaboric acid-based (3) with chelating ability in Table 2. each amine-based rust inhibitor having 4
Seven types were used, including a silicon-based chelating agent (No. 5), a titanate-based chelating agent (No. 5), a phosphoric acid/titanium-based chelating agent (No. 6), and an ethyleneamine-based chelating agent (No. 7).

In the experiments shown in Table 2, the rust inhibitor was mixed at a ratio of 1% to the solid content of the polymer.

Table 2 shows that nitrite-based, metaboric acid-based, and amine-based rust inhibitors with chelating ability are effective as rust preventive agents, and the combination of these with styrene/butadiene/acrylic modified polymers is most effective; showed the second most effective effect.

The polymer cement mixture composition of the present invention contains styrene-butadiene-acrylic modified polymer or styrene-butadiene as a polymer component, and contains nitrite-based, metaboric acid-based, and amine-based rust preventive agents with chelating ability as rust preventive agents. agent is added.

The compounding ratio of the rust preventive agent is 0.0% relative to the solid content of the polymer. 1
If it is less than 1%, the flash last suppression effect will be small;
If the temperature exceeds 0, the curing will be slow in the case of polymer cement. It has been confirmed through experiments that 1% to % is appropriate.

For the mortar of the structure of the present invention, Boltland cement or blast furnace cement, which had a high pH value and was not corrosive in the above experiment, was used as the cement, and granulated blast furnace slag and silica sand ( Mountain sand, river sand) is used.

Corrosion resistance can also be improved by incorporating flat pigments such as glass flakes and mica shear iron oxide into the mortar composition.

In addition, in the present invention, in order to densify the film of the polymer cement blend composition (improve corrosion resistance and improve the physical properties of the coating film), and to enable even thicker spray finishing using the same material, A combination of two types of fillers is blended.

This filler has a higher dispersion effect and a more densifying effect when mixed with the polymer in advance than when it is directly mixed with aggregates in powder form.

As a result of the experiment, the following trends were observed in the filler.

(a) Silica-based filler (325 mesh passing 98 or higher) Added amount from small to large Improved densification (b) Magnesium filler (325 mesh passing 9
8% or more) Addition amount from small to large Thickening effect, improvement in film-thickening properties The effect when the above filler is added as a part of the polymer cement mixture is expressed as the coating effect and flow value of each composition below. 3.

■ Basic composition (without filler) Blast furnace cement: Granulated slag ratio - 30:70 cement:
Polymer ratio: -71:29 Cement:water ratio: -70:30 ■ Silica filler: Magnesium filler: Added both to the basic composition at a ratio of -30:70.

■ Similarly, silica-based filler:magnesium-based filler - Both were added at a ratio of 50:50.

■ Similarly, silica-based filler:magnesium-based filler - Both were added at a ratio of 70:30.

The filler:polymer ratio was 40:60 in all cases, and the mixed composites were spray-painted using a mortar gun.

From the above table, in consideration of the coating effect (thick coating effect) and workability, the ratio of silica filler:magnesium filler was set to 50:50 in the present invention.

Furthermore, if an ultra-thick film is required for a special purpose, the following special filler can be added to the basic composition (without filler) in ① above at a ratio of 0.5 to 3.0% to the polymer, and the mortar gun can be used. Experiments have shown that it is possible to spray paint 8 to 15 times using the same method.The polymer cement produced by this method not only provides an ultra-thick film with one spraying, but also has excellent physical properties. It is extremely good, with no cracking during drying that tends to occur with thick films, and also has good adhesion to steel materials.

Examples are shown in Table 4 below.

Next, the excellence of the polymer-cement blend of the present invention as a corrosion-resistant coating for steel structures will be explained with reference to Examples.

Example: Polymer cement admixture compositions (1), (2), and (2) of the present invention having the blending ratios of composition components as shown in Table 4 were used as test products, and flash last was tested along with conventional products (a) and (b). Tests were conducted for corrosion resistance, paintability, adhesion to steel plates, corrosion resistance, etc.

In the above table, for the mortar structure, boltland cement or blast furnace cement is used as the cement, blast furnace slag, converter slag, and silica sand are equally used as the aggregate, and silica-based and magnesium-based fillers are used as the filler. Mixed in equal amounts.

As the polymer, styrene-butadiene or styrene-butadiene-acrylic modified polymer is used as a latex type polymer.

As the rust preventive agent, a nitrite-based rust preventive agent, a metaboric acid-based rust preventive agent, and an amine-based rust preventive agent having chelating ability are used.

In addition, tap water is used in an amount necessary for workability.

Note that the ratio of the mortar composition to the polymer in the present invention is not particularly limited, but is usually 95:5 to 80:
The range is 20.

The test results are shown in Table 5.

Among the items in Table 5, (1) The occurrence of flash last is 100X200
A polymer cement mixture composition was applied to a shot-blasted steel plate with a diameter of 3.2 mm, and after curing, the coating was peeled off and the state of rust on the steel surface was observed. It is.

(2) Paintability is the result of spray painting a polymer cement mixture onto a 1.000 x 1.000 x 4.4 shot blasted steel plate surface using a mortar gun.The diameter of the spray nozzle is 5 hours, atomizing air is 3.5~
At a pressure of 4 kg/cwt, the spray distance is 30-40
cIrL.

(3) Adhesion force with steel plate is 100 x 200 x 3
．． This shows the results of vertical tension applied to a film made by coating a 2 mm shot-blasted steel plate with a polymer cement mixture using a universal tensile tester. , tension jig 15X
15 mm, the jig adhesive was a two-component curing epoxy resin, and the experiment was conducted in a room temperature environment.

(4) Corrosion resistance was determined by coating a 100 x 20 x 32 shot-blasted steel plate with 5 x 1 coat of the polymer cement mixture composition, drying it indoors with a trowel for 28 days, and then placing it in saline solution at 40°C for 30 minutes. The results are shown after soaking for one day.

Conventionally, alkyd resin (oil-based) or coal tar epoxy resin-based paints have generally been used on the inner surfaces of ship cargo holds, land-based steel silos, and the like.

However, when loading coal into a ship's cargo hold, the paint film on the parts that come into contact with the cargo is severely damaged, and rust occurs from the exposed parts of the base material, which takes about $6 months for oil-based paints and less than 1 year for coal tar epoxy resin paints. There is a risk that the corrosion of the steel plate will progress to a significant degree if coal is subsequently loaded, and there is a case where the steel plate penetrated due to pitting corrosion after loading North American coal for two months.

In addition, since general cargo ships load various types of cargo alternately, if grains are loaded into a cargo hold that has rusted, it is necessary to repaint the cargo to prevent it from becoming contaminated, which increases the economic risk.

On the other hand, epoxy resin-based paints (
There are resin mortars (with aggregate) and polyester-based (glass flakes) mastic paints.

However, the former requires a film thickness of 3 to 5 mm or more and is expensive and has poor flexibility, while the latter has poor impact resistance and heat resistance and cannot be used with a shop primer system.Other commercially available wear-resistant paints are mainly used for road use. It was developed for use in trucks such as trucks, etc., and its corrosion resistance is questionable, and its application to ship cargo holds, land-based steel silos, etc. is difficult due to the construction method and price.

Against this background, we have found a paint that has both corrosion and abrasion resistance, is inexpensive in material cost, and is relatively easy to apply.

The present invention relates to a paint that is applied to structures that require both corrosion resistance and abrasion resistance, such as cargo boards of ships, land steel silos, etc., and that have a relatively large area.

Therefore, the gist of the present invention is as follows: ■ Good corrosion resistance and wear resistance.

■ The material price is low and is equal to or lower than the conventional coal tar epoxy system.

■ The film thickness is relatively thin (less than 2n) and has high OT flexibility, making it easy to apply to structures and has good coating workability.■ Relatively excellent heat resistance and impact resistance. , Adhesiveness with shop primer is good, and it is a good idea to use the shop primer system ■ Considering repair painting, adhesion with various organic paints is good ■ Taking into account loading of grains, With the aim of not containing or eluting substances harmful to humans, we have discovered a polymer cement (containing aggregate) paint that satisfies these conditions.

The structure and examples of the present invention are shown in Tables 6, 7, and 8 below.
and shown in Figure 3.4.5.

Table 8 shows the results of observing the appearance of the coating film after being immersed in various types of cargo for one month, and the cargo/distilled water ratio was 1/6 to 2/2.
2. The temperature was 50±5°C.

*1 *2 *3 *4 Polymer cent is applied to a 100 x 200 x 32 mm shot-blasted steel plate, and after hardening, the coating is peeled off and the state of rust on the steel surface is investigated.

1000X1000X4 Spray painting on my shot blasted steel plate surface with mortar gun, nozzle diameter 5%: atomizing air 35~4 k9/cyrt spray distance = 30~40 melon 100X2
The coating applied to a 00X32 shot-blasted steel plate was subjected to vertical tension in a universal tensile test.

Material 4> 14 days, tension speed 2.5/min, tension tool 15 x 15 mm, adhesive 2-component curing epoxy system, room temperature environment 100 x 200 x 3. It was applied to a shot-blasted steel plate with a thickness of 15 mm, dried indoors for 28 days, and then immersed.

However, as is clear from the table above, the conventional product b has three specifications.As is clear from the table above, the polymer cement mixture according to the present invention prevents the occurrence of flash last, which was a problem with conventional products, and can be sprayed in one coat using the same material. It has a high-quality finish and is superior in paintability, adhesion, and anti-corrosion performance to conventional products, and therefore has extremely excellent performance as a corrosion-resistant coating for steel structures.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between pH and corrosion in steel, and FIG. 2 is a diagram showing changes in pH of aggregate and cement. 3 to 5 are graphs showing the relationship between each coating system and the weight reduction rate, where FIG. 3 shows the degree of wear caused by bauxite, FIG. 4 shows the degree of wear caused by petroleum coke, and FIG. 5 shows the degree of wear caused by coal.

Claims (1)

[Claims] 1 A mortar consisting of cement, aggregate, silica filler, and magnesium filler, a styrene-butadiene water-dispersed polymer, and a rust preventive agent of 0.1 to 101% based on the solid content of the polymer as compounded components. Polymer-cement blend composition for steel structures