GB2093050A

GB2093050A - Pipe sealing compositions

Info

Publication number: GB2093050A
Application number: GB8203602A
Authority: GB
Original assignee: PRESS LEAKAGE CONTROL SERVICES
Current assignee: PRESS LEAKAGE CONTROL SERVICES
Priority date: 1981-02-12
Filing date: 1982-02-08
Publication date: 1982-08-25

Abstract

A method of sealing pipe joints against leakage after installation comprises the location of a mould around or within the pipe in the region of the leaking joint and thereafter introducing a polysulphide sealant composition into the mould which is allowed to set. The sealant is a formulation of a polysulphide compound which is initially flowable but sets to an elastomeric sealing composition after a time period. The sealant composition may be in two parts which are mixed before use and may contain, beside the polysulphide,

Description

SPECIFICATION Pipe sealing This invention relates to a method of pipe sealing. It is more specifically, but not exclusively, directed towards the sealing of joints between sections of gas carrying pipes.

It is known to seal leaking gas joints by clamping a rigid mould or flexible mould around the joint which serve to define an annular mould cavity into which a sealant compound is introduced which thereafter hardens or sets to form a bonded collar which seals the leak externally of the pipe.

Various sealant compounds have been used to seal leaking joints in this manner. In particular polyurethanes have been used to a major extent and to a lesser degree epoxy resins, polyesters and butyl mastics. All have disadvantages which renders their usage less than ideal.

Such known sealants have proved to have low resistance to long term (50 years) vibration, deflection, distortion loads and environmental resistance is uncertain. Further problems have arisen from poor adhesion to pipes and joint materials and these sealants have been susceptible to minute, non-visible moisture levels at the application stage which requires priming or air drying. Polyurethanes incorporate isocyanates which present toxic hazards and the reactions during mixing have been highly exothermic with associated dangers to the operator. Polyurethanes are oil based products which can be costly.

It is further known to use filled and extended polyurethane sealants which incorporate calcium carbonate filler and pitch or coal tar extender. Such formulations are difficult to repeat due to quality variations depending on the source.

Thus a problem arises in providing a sealant composition which avoids at least some of these disadvantages. Polysulphide polymers are known per se but have always been of thick consistency and unable to flow and could not therefore be considered as pipe sealant formulations.

It is an object of the present invention to provide a flowable sealant for pipes which has improved characteristics and substantially avoids the disadvantages of polyurethane sealants.

Accordingly the invention provides a method of sealing joints between sections of pipes using a polysulphide pipe sealant formulation which is initially flowable and thereafter sets after a time period.

The polysulphide may be a two part mix but it is to be initially flowable and hence pourable into a mould located around or within a pipe under normal in situ conditions to seal the leaking pipe or joint.

The invention further provides a method of sealing a pipe, in which method a mould is located around or within the pipe to define an annular cavity into which a sealant formulation is introduced, the formulation thereafter setting to produce a band of sealant, the method being characterised by the use of a polysulphide formulation which is initially flowable and sets after a time period.

By the use of selected additives a polysulphide elastomer has been produced which has the required initial flowability characteristic.

Example A two part mix of the following composition produces, by way of an example a polysulphide elastomer which is initially flowable and sets to form an effective and advantageous pipe sealant.

Part I % by weight Polysulphide Polymer 50.0 Anti-corrosive pigments 1.2 White pigment 1.2 Chalk filler 39.0 Toluene 8.0 Mixtures of Silanes s amine phenol 0.6 100.0 Part I % by Weight Polysulphide Polymer 50.0 Anti-corrosive pigments 1.2 White pigment 1.2 Chalk filler 39.0 Toluene 8.0 Mixtures of Silanes 8 amine phenol 0.6 100.0 The polysulphide polymer forms 25% of the mixed product which is cured ot hardened by the manganese dioxide in Part II. Use of the white pigment enables the operator to determine when mixing is complete by virtue of an overall grey appearance. The toluene acts as a thinner, solvent or diluent which evaporates during the hardening process.

The above parts I and II are thoroughly mixed and poured into a mould securely locatd about the pipe being sealed. After a period of time the formulation sets to form a leak sealing polysulphide elastomer which prevents gas seepage from the leaking pipe or joint.

The advantages obtained by use of polysulphide polymer to form an elastomer for sealing pipes are good long term performance, the mixing operation does not produce a highly exothermic reaction, there are no toxic isocyanates in the formulation and there are no toxic properties presently known of these ingredients. This formulation adheres excellently to the pipes and joints without priming and in particular the efficiency of the sealant is not reduced by moisture. The tolerance to water is excellent before, during and after application of the polysulphide formulation.

Claims

1. A pipe sealant formulation incorporating a polysulphide polymer which is initially pourable at ambient temperatures and sets after a time period to form a polysulphide elastomer.

2. A sealant according to Claim 1, comprising a two part formulation, a first part consisting of poly sulphide polymer admixed with a filler, the second part incorporating a suspending medium.

3. A two part sealant according to Claim 2, comprising a first part of polysulphide polymer, chalk filler, diluent, silanes and amino phenol and a second part of curing agent, suspending medium, tetramethyl guanidine and silane.

4. A two part sealant according to Claim 3, comprising in percentage by weight a first part of polysulphide polymer 50, anti-corrosive pigments 1.2, white pigment 1.2, chalk filler 39, toluene 8, mixtures of silanes and amino phenol 0.6 and a second part of manganese dioxide 60.2, low molecular weight suspending medium 39, tetramethyl guanidine 0.4 and silane 0.4.

5. A method of sealing a pipe wherein a mould is located around or within the pipe to define an annular cavity into which a sealant compound is introduced, the compound thereafter setting to produce a band of sealant, in which method the sealant is a formulation incorporating a polysulphide polymer which is initially pourable at ambient temperatures and sets after a time period to form a polysulphide elastomer.

6. A method according to Claim 5, wherein the sealant comprises a two part formulation, a first part consisting of polysulphide polymer admixed with a filler, the second part incorporating a curing agent and a suspending medium.

7. A method according to Claim 5, wherein the sealant comprises the formulation of Claim 3.

8. A method according to Claim 5, wherein the sealant comprises the formulation of Claim 4.

9. A method of sealing joints between sections of pipes using a polysulphide polymer formulation substantially as herein described.

10. The polysulphide pipe sealant formulation herein described and exemplified.