JPH06248226A - Coating for pipe-connecting screw - Google Patents

Abstract

PURPOSE:To provide a coating for a pipe-connecting screw excellent in low- temperature resistance, free from concern for water pollution due to the solvent therein and possibility of decreasing the sealing pressure due to the seal coating film thinning concomitant with evaporating the solvent with time. CONSTITUTION:The coating of precoating type is so designed that both film- forming component and slip-imparting component are adjusted to such respective viscosities as to be coatable in the form of solvent solution. The film-forming component consists mainly or wholly of an epoxy-, acrylic-, polyester-, or alkyd- modified silicone or fluorosilicone, while the slip-imparting component mainly or wholly of fluororesin powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoat type paint for pipe connecting screws for increasing the sealing property and screwability of pipe connecting screws of various pipes such as gas pipes and water pipes. In particular, the present invention relates to a coating material for pipe connecting screws, which is suitable for steel pipe screws that are prone to rust and the like.

[0002] Here, the pipe connecting screw means a female screw or a male screw in a screw type pipe joint such as a socket, a nipple, a bend, a cheese, a bush, a lock nut, a cap, a plug and a union, and further, both ends of a short water pipe. It is a concept including a threaded female screw or a male screw.

[0003]

2. Description of the Related Art Conventionally, in piping work for transferring drinking water, industrial water, etc., from the viewpoint of workability, a conventional seal tape (made of polytetrafluoroethylene) has been replaced by a liquid sealant applied on site. It is used a lot.

[0004]

However, in the case of the above liquid sealant, it is on-site construction and the solvent is 30-40.
%, It has been found that there are problems such as the possibility of water contamination by the solvent and the risk of reduction of the sealing pressure due to the thinning of the seal coating film due to evaporation of the solvent over time.

It is an object of the present invention to provide a paint for pipe connecting screws which can solve the above problems.

[0006]

The inventors of the present invention have made intensive efforts to solve the above-mentioned problems, and as a result, have conceived a paint for pipe connection screws having the following constitution.

A precoat type pipe connection screw coating material in which a film-forming component and a lubricity-imparting component are adjusted to have a viscosity that can be applied with a solvent, and any one of epoxy-modified, acrylic-modified, polyester-modified, and alkyd-modified Silicone or modified fluorosilicone is used as the whole or main component of the film forming component, and fluororesin powder is used as the whole or main component of the lubricity imparting component.

[0008]

[Detailed Description of Means] Next, a detailed description will be given of each configuration of the above means. In the following description, the mixing unit is a weight unit unless otherwise specified.

A. The coating material of the present invention is a precoating type pipe connecting thread coating material for increasing the sealing property and screwability of the pipe connecting thread, and the film forming component and the lubricity imparting component are prepared to have a viscosity that can be applied by a solvent. It is a prerequisite that Tenaiko is used.

B. The coating material of the present invention comprises a modified silicone or a modified fluorosilicone, which is either epoxy-modified, acrylic-modified, polyester-modified or alkyd-modified, as a whole or a main component of a film-forming component, and a fluororesin powder as a whole or a main component of a lubricant-imparting component. And (1) Examples of the silicone (polysiloxane) include dimethyl silicone and methylphenyl silicone, and examples of the fluorosilicone include those in which fluorine, a fluorinated alkyl group or the like is introduced into the side chain.

(2) With unmodified silicone or fluorosilicone, it is difficult to secure the adhesiveness to the surface of the pipe connecting screw, and with modified silicones other than epoxy-modified / acrylic-modified / polyester-modified / alkyd-modified, the coating film It is difficult to secure toughness.

The modification method is prepared by mixing (including a chemical bond) modified resin such as epoxy resin, acrylic resin, polyester resin, alkyd resin having a reactive group with the above silicone or fluorosilicone. The compounding ratio at this time is silicone / modified resin =
95/5 to 30/70, preferably 80/20 to 60
/ 40. When the amount of the modified resin is excessive, various functions of silicone such as heat stability and aging resistance are reduced.

(3) It is conceivable to use a solid lubricant other than the fluororesin, but it is difficult to secure a predetermined water pressure resistance (particularly after returning to 90 degrees) with a fluororesin.

Examples of the fluororesin include polytetrafluoroethylene (TPEE), polychlorotrifluoroethylene and the like, which are calcined and non-calcined. Among them, the effect of adding the fluororesin (the above-mentioned sealing property / sliding property) of the fired TPEE is remarkable. The particle size of the fluororesin is usually 0.1 to 300 μm.

(4) The paint for pipe connection threads of the present invention appropriately contains other chemicals such as an inorganic pigment, an anticorrosive agent, a surfactant, a curing agent, etc. in addition to the above-mentioned film-forming component and lubricity imparting component. To do.

The viscosity that can be applied with a solvent is usually 20 to 1000 cPs, and in the case of mass-production coating such as spraying and dipping, the lower viscosity is desirable and 20 to 500 cPs.
To prepare.

The solvent that can be used here is not particularly limited, but it is desirable that it has no strong odor and has low toxicity and flash point. Examples thereof include xylene, toluene, methylene chloride, turpentine oil, naphtha, methyl acetate, acetone, butanol, propanol, and mixed solvents thereof.

(4) The seal coating material prepared as described above is applied in advance to the threaded portion of the joint (regardless of male screw or female screw). The coating amount is usually 2 to 20 μ in the mountain portion.
m, preferably 2 to 5 μm, 5 to 200 μm at the valley,
Desirably, the thickness is 30 to 50 μm (all are dry film thickness). When solvent resistance and chemical resistance are required, the composition is heat-cured or preliminarily mixed with a curing agent in an amount of 0.3 to 3.0 parts based on 100 parts of the modified silicone and then cured at room temperature. The mode of heat curing is usually 100 to 200 ° C. × 3.
0 to 60 min.

[0019]

The operation and effect of the present invention has the following effects due to the coating composition for a pipe connecting screw of the present invention.

Since it can be applied in a factory instead of on-site construction, there is no risk of water pollution and reduction of sealing pressure due to thinning of the seal coating film due to evaporation of the solvent over time.

Since silicone is used as the base, the seal is excellent in heat stability, cold resistance, aging resistance, etc., and provides a good sealing property to the thread portion of the joint for a long period of time.

In order to solve the same problems as in the present invention, a packing joint having the following structure has been proposed (Japanese Patent Publication No. 59-45872).

"A packing joint characterized in that a packing coating layer containing fluororubber and polytetrafluoroethylene, which covers the threaded portion, is fixedly formed in advance on the threaded portion of the pipe joint having the thread." , Vulcanized fluorine rubber and polytetrafluoroethylene (PTE
F) and the applicable viscosity (1000 to 10,000 cPs
), And a pre-coating type paint for the screw part of the joint, which is prepared to have a solid content (20 to 80% by weight).

However, the present invention has the following advantages as compared with the coating material having the above-mentioned constitution.

Silicone has excellent cold resistance as compared with fluororubber, and the type of diluting solvent is not limited. The fluororubber is limited to those having a strong odor and having a strong odor such as isoamyl acetate.

In the case of the present coating composition, the coating viscosity is 20-100.
It can be as low as 0 cPs, which is desirable for factory mass production coating. In the case of fluororubber-based paint, it is 1000 to 10000 cPs.

[0027]

EXAMPLES Examples which were carried out to confirm the effects of the present invention will be described below.

A. The performance test was performed as follows.

(1) Preparation of assembly test body Each varnish shown in Table 1 was baked with PTFE (particle size 120 to
150 μm), and 30 parts of pigment and 2 parts of rust preventive agent are added to 100 parts of the total amount of varnish and PTFE,
Further, a solvent (xylene) was added so as to have a viscosity of 30 cPs and mixed to prepare each paint. Each paint thus prepared is applied by dipping onto the female screw (after degreasing treatment) of a steel pipe socket (2 inches). At this time, the dry coating film thickness was 2 to 5 μm in the peak portion and 30 to 50 μm in the valley portion.

After being left at room temperature for 24 hours, a steel pipe (2 inches) having an external thread on the end thereof is screwed in (final tightening torque: 20 kgf · m, 196J).

(2) Test Items Anticorrosion Force The above-mentioned assembled test body was subjected to a JIS Z 2371 salt spray test to visually observe the presence or absence of rust in the threaded portion.

Pressure resistance The above assembled test piece was rotated by 90 ° and rotated for 24 hours, and after 24 hours, tap water pressure (10 kgf / cm ² , 98 × 10 ⁴ Pa) was applied to test for water leakage.

Oxidation stability (aging resistance) According to JIS K 2220, that is, the oxygen pressure of the sample (paint) 7.
1 in a 7 kgf / cm ² (75.5 × 10 ⁴ Pa) cylinder
It was heated to 00 ° C., and the decrease in oxygen pressure after 500 hours was measured.

Adhesion of coating film Each coating material was dried to a thickness of 150 μm on a degreased mild steel plate.
It is applied so that it becomes m, and it is 100 according to JIS D 0202.
Make individual squares, attach cellophane adhesive tape and peel off rapidly, and count the number of remaining squares.

Water Dissolution Test Each paint (sample) was evenly applied to 100 cm ² on both sides of a glass plate of 5 × 15 cm, and left at room temperature for 24 hours to obtain a test piece. The test piece was washed with running water for 1 hour, then immersed in 1 L of distilled water prepared in advance, and after 24 hours,
The test piece was taken out. Then, the dipping solution was measured for odor, horse mackerel, chlorine consumption, potassium permanganate consumption, etc. in accordance with the Ministry of Health, Labor and Welfare Hygiene Inspection Guideline Water Test Method (Japan Waterworks Association).

B. Test results and evaluation Table 1 shows the test results. From the results shown in Table 1, it can be seen that the paints of the respective examples of the present invention are excellent in various properties as paints for pipe connection threads.

Water resistance due to the elasticity and water repellency of silicone,
Also, by combining the good cold resistance, heat resistance, weather resistance, long-term oxidation stability of silicone, and the toughness and metallizing adhesiveness of a specific modified silicone, the above paint for pipe connection threads is combined. It is estimated to show high performance as.

[0038]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C09K 3/10 M

Claims (3)

[Claims] 1. A pre-coat type paint for pipe connection threads, wherein a film-forming component and a lubricity-imparting component are adjusted to have a solvent-applicable viscosity, and any one of epoxy-modified, acrylic-modified, polyester-modified, and alkyd-modified is used. The modified silicone or modified fluorosilicone as described above is used as the whole or a main component of the film-forming component, and the fluororesin powder is used as a whole or the main component of the lubricity-imparting component. 2. The paint for pipe connection screw according to claim 1,
A method for sealing a pipe connecting screw, which comprises applying a seal coating film on a female screw portion or a male screw portion of the pipe connecting screw in advance. 3. A pipe connecting screw having a seal coating film formed of the seal coating material according to claim 1 on a female screw or a male screw.