JP2008274201A - Asbestos dust catcher and method for catching dust - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems wherein a conventional asbestos dust catcher containing sodium silicate as a main component is good in the permeability into asbestos-containing layer, but is weak in the adhesivity with asbestos because the dried film is hard and brittle so that the asbestos is apt to become dust at scrapping; also for a polyacrylic emulsion, the dried film is tough and good in adhesivity with asbestos, but the price per kg is higher by 10 times or more than sodium silicate so it is not economical; and the polymer cement process has defects that it is generally highly viscous so that infiltration into the asbestos layer is insufficient and drying and curing are delayed. <P>SOLUTION: This asbestos catcher well-balanced between practicality and economy comprises inexpensive sodium silicate as a principal component and is mixed with an acrylic copolymer emulsion or SBR latex which are good in compatibility, to improve hard and brittle properties and deficient adhesiveness of sodium silicate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention captures asbestos dust generated during dismantling and removal work for asbestos-containing coatings applied to architectural wall surfaces, ceilings or steel frames, and inner walls and ceilings of ships and vehicles for the purpose of heat insulation, fire resistance, and noise reduction. About coating materials that are sprayed and impregnated on the board surface to dry

Conventional dust trapping agents for disassembling asbestos include spraying agents mainly composed of sodium silicate disclosed in JP-A-63-282,161 (1986), and polyacrylic disclosed in JP-A-4-222,015 (1992). A spraying agent comprising an acid copolymer emulsion as a main component and Patent Application No. 350, 558 (2005), a mixed polymer cement construction method of Portland cement and styrene / butadiene copolymer latex is disclosed. Among these asbestos scavengers, those containing sodium silicate as the main component have good permeability in the asbestos-containing layer, but the dry film is hard and brittle and has poor adhesion to asbestos, and asbestos is easily dusted during disassembly. There is a problem. The problem with polyacrylic emulsions is that the dry film is tough and has good adhesion to asbestos, but the price per kilogram of sodium silicate is 10. Several times higher and uneconomical. The polymer cement method generally has a drawback that it has a high viscosity, does not sufficiently penetrate the asbestos layer, and is slow in drying and curing.

The present invention conceived a solution to the above problem by mixing an inexpensive and highly penetrable sodium silicate, and a strong and adhesive acrylic emulsion. Therefore, various polyemulsions were mixed with sodium silicate. Polyvinyl acetate emulsions, ethylene / vinyl acetate (EVA) emulsions, various acrylic copolymer emulsions, SBR latex, etc. are mixed with sodium silicate so that they are poorly compatible with sodium silicate and immediately gel or phase separate during storage. Met. Therefore, we were able to find only a few of many polymer emulsions that are compatible with sodium silicate. These products include two types of acrylic copolymer emulsion “Boncoat” manufactured by Dainippon Ink Chemical Co., Ltd., 14 types of LE-1043 and LE520 S, acrylic copolymer emulsion “Tomac Power” manufactured by Nippon Latex Processing Co., Ltd. and SBR Latex. “Tomac Super” was relatively compatible with sodium silicate. Therefore, in order to improve the adhesiveness of hard and brittle and asbestos of the main component and its dry film with inexpensive sodium silicate, the following tests were conducted on the permeability and adhesiveness of the mixture of highly compatible acrylic emulsion and SBR latex. It was.

A mixed liquid of 100 parts of sodium silicate (No. 3, solid 30%), 100 parts of Boncoat LE520S (solid 16%), 100 parts of water (H ₂ O) and 1 part of carboxin methylcellulose (CMC) (Test No. 3, A5 -2A-1) 100 _parts of H 2 O 100 parts, was used a mixture of 1 part of CMC. On the test specimen, 20 pieces of cotton cloth (0.3 mm thickness, 25 × 200 mm size) were deposited and fixed on a desk, and 20 g of the present mixed solution was evenly applied to the surface with a brush, and the surface was covered with the brush. After squeezing, pressing and drying for 24 hours, the specimen was cut to a width of 25 mm and used as a peel test specimen. The peel adhesion strength test method was JISK 6854, T-type peel method, and the peel adhesion strength in the range of 5 mm to 95 mm stroke was measured. At that time, the top two pieces of cotton cloth piled No. 1 and below. Data obtained by measuring peel strength using up to 9 adhesive cloths are shown in FIGS. Thus, the convex point maximum value 1330.92 g, the concave point minimum value 582.322 g, the convex part average strength 993.931 g, the concave part average strength 875.982 g, the concave and convex average of the measurement curve of the peel strength with a stroke of 5 mm to 95 mm. The strength was 934.967 g. Specimen No. 2-No. 9 has an uneven average strength of 416.064 g, 269.094 g, 240.111 g, 217.834 g, 203.96 g, 191.998 g, 168.165 g, and 137.284 g, respectively. It was found that the mixed solution of A ₅ -2A-1 had satisfactory adhesive strength and good permeability.

Comparative Example 1

Acrylic acid copolymer LE 520S 100 parts, H ₂ O 100 parts, CMC 1 part mixed compounding test No. FIG. 3 shows the measured values of the peel adhesion strength of the specimens applied to and dried on the cotton cloth in the same manner as in Example 1 using 3A-5B. Thus, the convex point maximum value 745.394, the concave point minimum value 381.438 g, the convex point average value 535.366 g, the concave point average value 458.196 g, the convex and concave average value 496.181 g, the bottom end No. 8 had an average roughness of 202.123 g, and sufficient adhesive strength and permeability were good. However, the adhesive strength is slightly lower than that of Example 1, and the unit price per kilometer is extremely high.

Comparative Example 2

As a result of measuring the adhesive strength of cotton cloth similar to the above with a composition of 100 parts of sodium silicate (solid 30%), 100 parts of H ₂ O and 1 part of CMC, the adhesive film was glassy hard and brittle and immediately after the peel test The bonded cotton cloth broke and became impossible to measure.

As shown in Figure 4 , sodium silicate (solid 30%) 100 parts, acrylic emulsion LE520S (solid 16%) 100 parts, 75 parts, 50 parts, 25 parts, 15 parts, 5 parts, and reduced to H ₂ O When the peel adhesion strength was measured in the same manner as described above with a mixture of 100 parts and 0.5 parts of CMC, the maximum strength of the convex points was 738 g, 537 g, 480 g, 245 g, 125 g, and 0 g, and the unevenness average values were 420 g and 396 g, respectively. 166 g, 78 g, 45 g, 0 g. Thus, as the acrylic emulsion was gradually reduced from 100 parts to 5 parts with respect to sodium silicate, the adhesive strength gradually decreased, and in No. 6 part 5, the adhesive strength became zero.

100 parts of sodium silicate (solid 30%), 100 parts of acrylic emulsion (Nippon Latex Tomac Power, solid 45%), 120 parts of H ₂ O, and 1.2 parts of CMC are used to separate cotton cloths as in Example 1. As a result of measuring the adhesive strength, the adhesive cloth No. The maximum convex point strength of 1 was 2968 g, and the adhesive strength of the ninth sheet was 466 g. It was found that the peel adhesion strength of Example 3 was significantly stronger than that of Example 1. The reason is that the solid of the former acrylic emulsion is 16%, while the latter is as high as 45%.

Cotton similar to Example 1 with a mixture of 100 parts of sodium silicate (solid 30%), 100 parts of SBR latex (Tomac Power KT 9125C, solid 45%), 130 parts of H ₂ O and 1.3 parts of CMC from Nippon Latex Processing Co., Ltd. As a result of measuring the adhesive peel strength of the cloth, the maximum convex point of the upper first test piece was 1990 g, and the maximum convex point of the lowermost eighth sheet was 1133.6 g. Very good permeability and high peel adhesive strength. showed that. Next, the cotton cloth adhesion test piece was allowed to stand for 3 days, and the peel adhesion strength was measured immediately after being immersed in H ₂ O (25 ° C.) for 120 minutes. .2g, the lower 8th sheet 705.7g, it was found that the water resistance is quite good

Asbestos mastic spray plates (thickness of 3 mm, 15 × 25 cm dimensions) were coated evenly on the front and back surfaces of 150 g, and test pieces were dried and cured at room temperature for 3 days, and the asbestos dust test was performed as follows.
(1) Testing organization:
NPO Japan Housing Organization 2-8-11 Kawana Building, Yaesu, Chuo-ku, Tokyo
TEL 03-6241-0875
(2) Asbestos detector in dust: Olympus BX51 phase contrast microscope (3) Test method:
In an absorbent bag (18-liter polyethylene bag), the asbestos spray plate coated with the composition of Example 3 on the surface and dried is broken with both hands to break up into pieces of 5 to 20 mm, and the bag is sealed with a rubber ring, immediately before the test. Holding the closed bag in hand and shaking it three times to generate dust, sucking the air containing dust with a thin pipe and depositing the dust on the microscope glass plate, and then using a dispersion staining analysis method to make a microscope ( A photograph measured at a refractive index of 1.686 and a magnification of 40 times is shown in FIG. The analysis results are as follows.
(I) In three specimens of the test version without application of the scavenger, asbestos fibers were found to be MAX in 10 particles, and 10 particles were confirmed. (On photo)
(Ii) Asbestos fibers were not confirmed at all in the test piece in which the scavenger was applied to one side and both sides. (In the photo, below)

The conventional method of disassembling an asbestos-containing board has been dismantled and peeled randomly by hand or using equipment. In this construction method, there was a risk that asbestos dust would not be captured 100% and would re-scatter into the air due to random peeling and impact of the board. The asbestos capturing method of the present invention not only penetrates into the board, but also cuts a 30 × (30 to 120) cm square on the board surface in advance until it reaches the base with a cutter or the like. Applying the scavenger by spraying and penetrating the inside of the board, forming a tough film on the surface, carefully peeling each of the squares cut with a plastering iron etc. at the time of dismantling and arranging them closely on the floor Then, the backside is lightly sprayed with the scavenger, and it will soon be deposited to a height of 30-50 cm, tied to a cross with a string, and then stacked on a track. Such a construction method is not bulky with trucks compared to conventional unsorted demolition waste, and the amount of loading and landfill per vehicle is greatly increased, which is economical, and asbestos dust during loading and landfilling The risk of is greatly reduced.

There are countless asbestos-containing cement slate boards already installed on the walls and ceilings of schools, gymnasiums, factories and warehouses nationwide. It takes a huge amount of money and effort to disassemble and paste these alternatives. Asbestos is also contained in spray coatings containing heat-insulated asbestos on the inner walls of large ships, boilers, blast furnace main bodies and piping, and piping coating layers of hot spring coolers. Instead of disassembling these asbestos-containing layers, a method of semi-permanently preventing asbestos scattering by applying an aqueous paint prepared by mixing a pigment such as titanium white to the asbestos scavenger of the present invention was devised. The paint composition is asbestos-containing, based on kneaded water-based paint consisting of 25% potassium silicate (30% solid), 10% acrylic copolymer emulsion (45%) titanium white, 10% talc 15% calcium carbonate powder, 30% water. Apply and dry the material with airless spray.

The invention's effect

Asbestos-containing mastic boards sprayed on the walls of buildings, ceilings and steel as well as ships and vehicle interiors were widely used in schools and gymnasiums. Recently, asbestos pollution continues. In particular, asbestos dust from demolition work and aging of buildings is a serious pollution. As the asbestos scattering prevention method, a scavenger containing sodium silicate as a component or a scavenger containing an acrylic copolymer emulsion as a main component is known. The former, sodium silicate, has good permeability and low price on asbestos board, but the dry cured film is glassy hard and brittle and lacks adhesion to asbestos, and rescatters and hardens during dismantling and transportation landfill work. There was a defect that the water resistance of the membrane was poor and that the demolition waste was piled up and washed away by rainwater during transportation. The dry film of the latter acrylic co-emulsified emulsion is tough and has adhesion and water resistance, but its unit price per kilometer is 10 times higher than the former (500 yen or more), and the price has increased due to the recent oil shock. It has become a tendency. Therefore, the present invention is based on an acrylic copolymer emulsion or styrene having a good compatibility with sodium silicate as a main component. We have devised an asbestos dust trapping agent that mixes butadiene (SBR) latex and complements both, and has achieved good results in various tests.

The conventional method of disassembling an asbestos-containing board has been dismantled and peeled randomly by hand or using equipment. In this construction method, there was a risk that asbestos dust would not be captured 100% and would re-scatter into the air due to random peeling and impact of the board. The asbestos capturing method of the present invention not only penetrates into the board, but also cuts a 30 × (30 to 120) cm square on the board surface in advance until it reaches the base with a cutter or the like. Applying the scavenger by spraying and penetrating the inside of the board, forming a tough film on the surface, carefully peeling each of the squares cut with a plastering iron etc. at the time of dismantling and arranging them closely on the floor Then, the backside is lightly sprayed with the scavenger, and it will soon be deposited to a height of 30-50 cm, tied to a cross with a string, and then stacked on a track. Such a construction method is not bulky with trucks compared to conventional unsorted demolition waste, and the amount of loading and landfill per vehicle is greatly increased, which is economical, and asbestos dust during loading and landfilling Greatly reduces the risk of

As shown in Example 7, a method of applying and drying an aqueous paint obtained by mixing a pigment such as titanium white to the scavenger of the present invention onto an existing asbestos-containing cement slate plate is semipermanently performed without disassembling and replacing the substitute product. Generation of dust can be prevented. In addition, the thermal insulation coating of large vessels, boilers, blast furnaces, hot spring water storage tanks, and methods of preventing pipe coating prevent the dismantling of the asbestos-containing layer and the replacement work, and enormous economic effects can be expected.

The adhesive strength of the unevenness | corrugation point of the correlation curve of nine adhesive cloths is applied and dried on the deposition surface of 20 cotton cloths using the asbestos capture agent of Example 1, and is a peeling curve. The correlation curve figure of the adhesive strength of FIG. 1, and a stroke. The chart of the maximum value and average value of the convex and concave points of the correlation diagram of the adhesive strength and the stroke of the acrylic copolymer homo-capturing agent of Comparative Example 1. The correlation diagram when the acrylic copolymer emulsion is reduced to 70 parts to 5 parts with respect to 100 parts of sodium silicate of Example 2, and the graph showing the adhesive strength of the convex point maximum value and the uneven average value. The test result which deposited the asbestos dust which generate | occur | produced by grind | pulverizing the test piece which apply | coated the capture | acquisition agent of Example 3 to the asbestos containing spray board surface, deposited on the glass plate, and measured the presence or absence of asbestos fiber with a microscope.

Claims (4)

As an asbestos dust trapping agent, a polymer emulsion (latex) (solid content 15 to 60%) 20 to 20 parts which is compatible with 100 parts of an aqueous solution (solid content 30 to 60%) of alkali silicate (Na, K, Li) 100 parts, water (H ₂ O) 20-200 parts, thickener (CMC, HEC, polyacrylic acid soda, etc.) 0-2 parts mixed composition Copolymer emulsion of acrylic acid ester (C ₂ -C ₄ ) and styrene or methacrylic acid ester (C ₁ -C ₄ ) (solid content 15-60%) or copolymer of styrene or methyl methacrylate and butadiene as polymer emulsion Use latex with good compatibility with sodium silicate. Asbestos dust trapping method: Asbestos-containing mastic material (binder: cement or polymer adhesive) coated and dried on walls, ceilings or steel frames, using a cutter or the like in advance on a thin layer surface of 20-120 cm square (concrete etc.) The incision is made until it reaches, and the scavenger of the present invention is blown into the spray board with airless spray, etc., and after drying, the square cut pieces are peeled off one by one with a plastering iron and placed on the floor. The construction method is to pile up and fasten with a string to the cross, and then load and transport it on a truck to landfill. The existing asbestos-containing building board (board) and heat insulation heat insulation coating shown below using an aqueous paint in which a pigment such as titanium white is mixed with an asbestos scavenger mixed with potassium silicate and acrylic copolymer emulsion in the alkali silicate of the present invention A method of spraying asphalt to prevent asbestos scattering semipermanently.
(1) Asbestos-containing cement slate plates attached to walls and ceilings of gymnasiums, etc. (2) Asbestos-containing mastic coating painted on the inner walls and ceilings of steel ships (3) Boiler body and piping insulation coating (4) Blast furnace body Insulation coating for piping (5) Hot spring water storage cooling tank and piping coating