JP2011121035A - Method for peeling liquid gasket on joint surface and release agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To peel off a coating film of a liquid gasket at a low cost. <P>SOLUTION: A method for peeling off a liquid gasket on the joint surface includes the steps of: applying a release agent for softening the coating film onto the coating film of the liquid gasket, which is stuck to the joint surface in a solidified state and remains as it is when the assembled/joined part of an instrument is disassembled or disassembled and reassembled, and penetrating the applied release agent into the coating film to soften/plasticize the coating film; and peeling off the softened/plasticized coating film from the surface joined when the instrument is assembled. The release agent to which THF or THF and MEK is added as an additive by 4-12 wt.% in order to enhance the swelling properties of the coating film, is used. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention is mainly used in a pipe joint of a nuclear power generation or thermal power generation facility and peels off a liquid (paste-like) gasket packing that remains and adheres at the time of disassembly / disassembly, and a peeling method and peeling of a liquid gasket packing on a joint surface It relates to the agent.

In addition to thin gasket gaskets being inserted into assembly joints such as pumps and pipes of conventional power generation facilities, silicon and alkyd systems are mainly used for each joint surface in order to improve airtightness and liquid tightness. A liquid (paste-like) gasket packing as a material is applied.
Since this liquid packing strongly adheres to the joint surface in the solidified state with elasticity after evaporation of the solvent after assembly, it remains attached when disassembling and reassembling during periodic inspections, repairs, maintenance, etc. It is necessary to remove the liquid gasket. In this removal operation, a release agent mainly composed of an organic solvent is applied and dissolved and washed, or mechanical removal is performed using a wire brush or the like.

  Among the above, for alkyd liquid gasket packing that is particularly suitable when seawater is used as cooling water, it is classified as a second type organic solvent under laws and regulations such as organic solvent poisoning prevention regulations, and as a first petroleum category under the Fire Services Act. What is marketed as a classified “gasket remover” is used as an effective release agent in terms of release performance and workability.

However, there is currently no effective release agent for silicon-based liquid gasket packing.
In addition, although it is not effective for gasket packing, as a release agent that swells and softens the paint film on the wall surface of general buildings such as mortar and the paint film on the surface of steel structure, Patents 1, 2 and the like developed by Yamaichi Chemical Co., Ltd. are known. However, softening (swelling) is insufficient for liquid gasket packing, There is no effectiveness in peeling.

Japanese Patent Laid-Open No. 10-279850 Japanese Patent No. 3985966

  However, in the conventional organic solvent and mechanical removal methods described above, the former uses an organic solvent, which requires ventilation in the work area and wearing protective equipment such as a protective mask, which may have potential health effects on workers. Concerned. Since the latter is a mechanical removal operation, the removal efficiency is poor, and there is a concern that the piping base material is damaged and the dimensional accuracy is impaired.

In addition, the release agent that has been used in the past is composed of strong solvents such as THF (tetrahydrofuran), MEK (methyl ethyl ketone), methanol, etc., so there are safety restrictions such as being restricted by the Industrial Safety Law and Fire Service Law. there were.
In particular, in contrast to alkyd-type liquid gaskets that are mainly used for seawater and have low versatility, silicon-type gaskets that are versatile and widely used are rubber-like because the resin component has a high purity, so they are slightly swollen. It cannot be dissolved (softened) with an organic solvent.
Further, the conventional method has a drawback that an eraser-like residue remains after the coating film is removed.

  In response to the above-described problems, the present invention does not allow the coating film of the liquid gasket packing to dissolve and flow out due to the solvent during the disassembly and reassembly of the joints of the above-mentioned devices, and to prevent environmental pollution, worker health damage and the joint surface. It is an object of the present invention to provide a method for performing an efficient peeling operation that can prevent damage and the like.

  The method of the present invention for solving the above-mentioned problem is as follows. First, when disassembling or reassembling the assembly joint portion of the equipment, the liquid gasket packing that remains attached to the joint surface in a solid state is applied. A method of applying a release agent that softens the coating film to the film, softening the coating film by infiltrating the coating film and plasticizing the film, and peeling the coating film from the joint surface at the time of assembly, In order to enhance the swelling property of the coating film, the release agent is characterized by using THF or THF and 4% to 12% by weight of THF and MEK.

  Secondly, the coating film of the liquid gasket packing is a coating film mainly composed of a silicon-based material, the release agent is composed mainly of a dibasic acid ester, N-methyl-2-pyrrolidone, benzyl alcohol, organic acid, A surfactant and a thickener are included, and the additives are THF and MEK.

  Thirdly, the coating film of liquid gasket packing is a coating film mainly composed of alkyd material, and the release agent is composed mainly of water and ethyl diglycol acetate, and BTG, acetone, butyl diglycol acetate and thickening agent. And the additive is characterized by being THF.

  Also, the release agent used in the above method is first applied to the joint surface in a disassembled state that can be disassembled and reassembled while being sealed through the paint film of the liquid gasket packing. A release agent that is softened and plasticized so as to be separated from each other, and is characterized by adding 4 w% to 12 w% of THF or THF and MEK in order to enhance the swelling property of the coating film.

  Secondly, the coating film of the liquid gasket packing is a coating film mainly composed of a silicon-based material, the release agent is composed mainly of a dibasic acid ester, N-methyl-2-pyrrolidone, benzyl alcohol, organic acid, A surfactant and a thickener are included, and the additives are THF and MEK.

  Thirdly, the coating film of liquid gasket packing is a coating film mainly composed of alkyd material, and the release agent is composed mainly of water and ethyl diglycol acetate, and BTG, acetone, butyl diglycol acetate and thickening agent. And the additive is characterized by being THF.

According to the present invention configured as described above, the following effects can be obtained.
(1) Since the coating film is peeled off without being completely dissolved, it is swollen and softened, so there is no environmental pollution as in the case of dissolution cleaning, and the worker's work by floating harmful gases and mist in the atmosphere. There is no need to wear protective equipment for health damage and prevention of health damage.
(2) It can be swollen only by the application of a release agent, and the paint film that has been softened is mechanically peeled off, so that the work efficiency is improved and the joint surface is damaged as with conventional wire brushes. In addition, since there is no remaining coating film component, more complete peeling can be realized as a whole.
(3) Particularly effective for silicon-based gaskets that were impossible or incomplete by conventional methods, and as a result, effective coating peeling can be easily performed regardless of the material of the current liquid gasket packing. it can.
(4) Use of a release agent consisting of a weak solvent such as dibasic acid ester, N-methyl-2-pyrodrine, water, and ethyl diglycol acetate as the main component is highly safe in handling and strict in terms of safety There are no legal restrictions (see Table 10).

Hereinafter, the embodiment of the present invention will be proved based on specific examples. In particular, an object of the present invention is to solve the problem of peeling of the liquid gasket at the joint at the inspection and maintenance work site of the nuclear power plant (equipment). Therefore, since it is difficult to conduct an actual on-site experiment, a steel plate and a stainless steel plate were used as test pieces (plates) under the same conditions as the pipe joint surface, and a liquid gasket was applied to these test pieces and dried and solidified. On the other hand, it was based on a method in which an original release agent was applied and swelled and softened for release.
Hereinafter, examples of the present invention will be described in detail based on the results of tests (experiment) conducted by the inventors.

1. Materials used (1) Liquid gaskets to be peeled Liquid gaskets currently in general use were investigated in the manufacturer's catalog, MSDS (Product Safety Data Sheet), website, etc. The results are shown in Table 1. The symbol display of the object follows the manufacturer's part number (model).

(2) Base material (test plate) on which liquid gasket is applied
There are two types of test plates, carbon steel (SS400 ... left-rolled steel for general structure) and stainless steel plate (SUS304), which are the same as the current steel materials, and the substrate is smooth and scratched. Since the adhesion of the liquid gasket can be changed, two types, scratched and scratched, were created. The breakdown is shown in Table 2.
Note) All stainless steel is hairlined.

(3) Release agent 1) Arrangement of required performance Based on the investigation of existing commercial products and the purpose of this research, the required performance for the release agent was arranged. The subject of the present invention is “development of a release agent for a liquid gasket that does not use an organic solvent”, but there is no release agent that does not strictly use an organic solvent. Therefore, compared with the current product, the safety of the main component (organic solvent) of the release agent, etc. (worker / environmental impact, etc.) is considered without sacrificing the release performance and considering the effect on the base material. Emphasis was placed on improving

2) Examination of prototype (examination of main component and component composition)
Applicable laws such as the Industrial Safety and Health Act and the Fire Service Act need to be relaxed. The main components of the current product (gasket remover) are composed of strong solvents such as THF (tetrahydrofuran), MEK (methyl ethyl ketone), and methanol. Therefore, it is necessary to examine the main components that are more lenient and safer.
The objects to be peeled are alkyd and silicon, and alkyd has good solubility in common organic solvents. Silicon is a rubbery resin with high purity, so it cannot be dissolved with an organic solvent. However, since it swells depending on the polarity of the solvent, safety is taken into consideration, and the optimal balance of solubility parameters provides higher safety such as odor and skin irritation compared to current products, and applicable laws and regulations are relaxed. Aimed at release agent.

3) Prototype production Based on the above-mentioned arrangement of required performance and examination of the composition of the prototype, we examined and produced a prototype that is safer than the current product and loosely regulated. Two types of prototypes were created, and prototype 1 was based on a higher alcohol solvent. Prototype 2 is water-soluble and does not comply with various laws and regulations such as the Fire Prevention Law, Occupational Safety and Health Law, Organic Solvent Poison Prevention Regulations, PRTR, etc. Table 3 shows an overview of the prototype. In addition, the developed release agent developed this time has a high performance of swelling and softening to silicon as a performance feature, and in terms of safety, it is mainly composed of higher alcohol solvent. (Acute toxicity is low), and there are characteristics that existing stripping agents do not have. Tables 4 and 5 are the composition tables of prototypes 1 and 2 used in this experiment.

Remarks 1) DBE (Dibasic acid ester)
High solubility and high flash point. It has high biodegradation and is characterized by fruit odor. In addition, because the safety is high, the target liquid gasket is effectively softened.
2) NMP
Auxiliary component of DBE (dibasic acid ester). Combining them will lead to further improvement in softening performance. The blending deteriorates the stability over time such as component separation, but the peeling effect is increased by the composite, and the blending balance of about 15% to 20% is optimal.
3) Benzyl alcohol
Like NMP, it is an auxiliary agent for improving the softening performance of DBE, the main component.
* The main component with high safety can be realized by the combination and optimum balance of 1), 2) and 3).
4) MEK, THF
Added to give excellent swelling to silicone rubber. Experiments confirmed the effectiveness of the formulation.
5) Other ingredients
Mega-Faque (surfactant) ... for promoting penetration and stability of properties.
Organic bentonite: To ensure adhesion during vertical surface coating.
Oil red ............ Colored to distinguish the painted area.

Remarks 1) Ethyl diglycol acetate
Increases solubility and safety. It is a water-soluble organic solvent used as the main component in order to effectively soften the liquid gaskets that are the subject.
2) Butyltriglycol
Auxiliary component of ethyl diglycol acetate. By combining with NMP of Prototype 1, the softening performance is further improved. The compounding balance of about 5% to 10% is optimal for the peeling effect of the composite.
3) Butyl diglycol acetate
Like butyltriglycol acetate in 2) and NMP in prototype 1, it is an auxiliary agent for improving the softening performance of ethyldiglycolacetate, which is the main component, and aims to improve the peeling effect of the composite.
* The main component with high safety can be realized by the combination and optimum balance of 1), 2) and 3).
4) Acetone, THF
Added to improve the swelling property to silicone rubber. Experiments confirmed the effectiveness of the formulation.
5) Other ingredients
Megafuck (surfactant) ... For state stability.
Organic bentonite: To ensure adhesion when vertical surfaces are applied.
Colored dye: Colored to distinguish the coated area.

2. Peeling performance evaluation test The removability, safety, and influence on the base material of the liquid gasket applied to the test plate and dried were evaluated. In addition, as a target area, a conventional product (current product gasket remover) was used for comparative evaluation.

(1) Test method A certain amount of release agent was applied to various test plates, and the degree of softening (removability) was evaluated. The coating amount of the release agent was about 200 g / m ² which is the same as the coating amount of the current liquid gasket.

(2) Evaluation Criteria After applying the release agent, the removability was evaluated after about 5 hours for the alkyd system and about 24 hours for the silicon system. The evaluation was a sensitive evaluation (pressed with a metal skin). In addition, work efficiency (workability) was evaluated. Table 6 shows the evaluation criteria for removability, and Table 7 shows the evaluation criteria for work efficiency.

(3) Evaluation result of test Table 8 shows the test result of removability and Table 9 shows the evaluation of workability.

  As a result of comparison between prototype 1 and prototype 2, the removal performance of prototype 1 was excellent overall. Prototype 1 had good removability for all liquid gaskets, but 1212 (high viscosity type) required a little force for removal. The working time was 10 minutes / 8 sheets for alkyd, including removal and wiping of the liquid gasket, 1212 for silicon was about 30 minutes / 8 sheets, and other silicon was about 20 minutes / 8 sheets. Conventional products are compatible with alkyds, but silicon has a lot of rubbery residue on the steel surface.

(4) Evaluation of relationship with applicable laws and regulations Table 10 shows a comparison of applicable laws between the conventional gasket remover and prototype 1 and prototype 2. Conventional products fall under the Occupational Safety and Health Act, organic solvent poisoning prevention regulations, and dangerous materials (highly hazardous first petroleum) under the Fire Service Act. Prototype 1 corresponds to the Second Petroleum of the Fire Service Act, but it can be made not to fall under other laws and regulations unless the amount of solvent added is excessive. Prototype 2 is not subject to legal restrictions. See MSDS (Product Safety Data Sheet).

Note 1) Risk level of the Fire Service Act High risk level-1st petroleum> 2nd petroleum> 3rd petroleum-small risk 2) Chemical emission control management promotion law (PRTR) depends on chemical substances A law that aims to allow businesses to actively participate in environmental conservation in order to prevent environmental pollution and damage to human health. PRTR: Pollutant Release and Transfer Register Environment Agency / Ministry of International Trade and Industry “Outline of Law” (July 1999) Excerpt

3. Comprehensive evaluation (1) Cost comparison evaluation Prototypes 1 and 2 are less likely to generate residual deposits (eraser-like shape) that are likely to occur in the current product, so the time required for finishing after the removal is the conventional product. There are few compared. Accordingly, the overall process leads to a reduction in work time, and the cost reduction effect is high. Table 11 shows the cost trial calculation table.

(2) Comparison of work efficiency In the removal work of conventional products, alkyd can be easily dissolved and removed, but silicon is not sufficiently swollen and softened, and the residue (residue) from the gasket is erased. It easily adheres to the steel surface and takes time for post-treatment such as wiping.
Prototype 1 and Prototype 2 are not immediately effective compared to conventional products, but alkyd-based materials can be easily dissolved and removed in about 5 hours. Since it can be removed in the form of a film by weakening the adhesive force, the working efficiency is improved.
The prototype 1 and prototype 2 developed in this study are superior in removal and work efficiency compared to the conventional gasket remover, but the prototype 1 is more comprehensive than the prototype 2. Highly effective.

(3) Comparative evaluation of environmental safety The conventional products are applicable to the First Petroleum of the Fire Service Act and the Occupational Safety and Health Act, organic solvent prevention rules, etc. Concerns about the impact on the environment.
As mentioned above, the laws and regulations concerning the prototype are more lenient than the conventional products. In addition, since the boiling point of the main component is high, the generation of VOC (volatile organic compounds) is small, the contamination of the work environment such as an increase in the concentration of the organic solvent is low, and overall safety is high and the burden on the operator is low.

(4) Comparative evaluation of the influence on the base material The influence on the base material is not concerned with corrosion or the like because the pH of the component is neutral. Further, the time required for post-processing finishing such as a paper file or a brushing process is short, and the piping base material is not polished more than necessary, so that there is little concern that the dimensional accuracy is impaired.

4). Addition amount of MEK, THF, acetone, etc. In this example, the addition amount of MEK, THF, acetone, etc. with respect to prototypes 1 and 2 was 4%, and the total was adjusted to 8%. Peeling performance and workability are best when it is within a range of less than 12 w%. If it exceeds this range, the peelability is poor and the workability is also lowered.

  The method of the present invention can also be applied to the joint surface of the lid portion of the pipe joint portion of the nuclear power generation equipment, the general thermal power, the pipe joint portion of general equipment other than the hydroelectric power plant equipment, and the bodies of various casings.

Claims (6)

  When disassembling or reassembling the assembled joints of equipment, apply a release agent that softens the coating to the coating film of the liquid gasket packing that remains attached to the joint surface in a solid state. A method of softening and plasticizing the coating film by infiltrating the film, and peeling the coating film from the joint surface at the time of assembly, wherein THF is used as an additive to increase the swelling property of the coating film to the release agent. Or the peeling method of the liquid gasket packing of the joint surface using what added 4 w%-12 w% of THF and MEK.   The coating film of liquid gasket packing is a coating film mainly made of silicon-based material, the release agent is mainly made of dibasic acid ester, N-methyl-2-pyrrolidone, benzyl alcohol, organic acid, surfactant And a thickener, and the additive is THF and MEK.   The coating film of the liquid gasket packing is a coating film mainly composed of an alkyd material, the stripping agent is composed mainly of water and ethyl diglycol acetate, and BTG, acetone, butyl diglycol acetate and a thickener are used. The method for stripping a liquid gasket packing on a joining surface according to claim 1, wherein the additive is THF.   Peeling that is applied to the joint surface in the disassembled state that can be disassembled and reassembled while being sealed through the coating film of the liquid gasket packing, and is softened and plasticized so that the coating film can be mechanically separated. A release agent for a liquid gasket packing on a joint surface obtained by adding 4 w% to 12 w% of THF or THF and MEK in order to increase the swelling property of the coating film.   The coating film of liquid gasket packing is a coating film mainly made of silicon-based material, the release agent is mainly made of dibasic acid ester, N-methyl-2-pyrrolidone, benzyl alcohol, organic acid, surfactant And a thickener, and the additives are THF and MEK.   The coating film of the liquid gasket packing is a coating film mainly composed of an alkyd material, the stripping agent is composed mainly of water and ethyl diglycol acetate, and BTG, acetone, butyl diglycol acetate and a thickener are used. 5. The release agent for a liquid gasket packing on a joining surface according to claim 4, wherein the additive is THF.