BR112012010421B1 - flexible pipe stiffener - Google Patents

Abstract

flexible conduit stiffener. The invention relates to a flexible conduit stiffener (12) made from a polyurethane elastomer composition which is obtained from a diphenylmethane diisocyanate (mdi prepolymer) prepolymer composition. It is then cross-linked with a polyamine to form the polyurethane elastomer composition capable of being formed to make the stiffener.

Description

“FLEXIBLE CONDUCT ENRIJECEDOR”

The invention relates to a stiffener for flexible duct.

The stiffeners are placed around the ducts in places where a flexible duct will suffer strong stresses induced by the movements of the vessel or waves. A stiffener consists of a structure of plastic material conically shaped having a length of a few meters and intended to surround the duct. By reinforcing a flexible duct with a stiffener at the most requested location, it prevents the duct from bending beyond its minimum radius of curvature beyond which the duct would suffer irreversible damage to its structure.

The flexible ducts that raise fluids (hydrocarbons, for example) from the wellhead are connected to the surface installation by passing through a steel guide tube that can be straight or bent “i-tubé” or “J -tubé ”respectively in English. Several guide tubes are provided on the surface installation. When the flexible duct rises again, it is guided and extracted through a guide tube to connect the end of the duct to the surface installation. In operation, the amplitude of the movements of the flexible conduit generated by the wave movements can generate a change in the structure of the flexible conduit in the vicinity of the guide tube, for example. To prevent such damage to the flexible conduit, a stiffener surrounds the flexible conduit in the vicinity of the guide tube. The stiffener is then attached to the end of the guide tube by a clamping collar in a known manner.

The stiffener is usually located under the workstation of the surface installation, in an immersed or partially immersed environment. In addition, the stiffener undergoes numerous stretching and compression stresses generated by the movements of surface installation and the flexible duct under the effect of marine currents, wind and / or waves. The conditions experienced by the stiffener could lead to premature aging of the plastic material in the long run that could impair the integrity of the flexible conduit.

To limit these phenomena, the stiffeners are manufactured from plastic material that has good resistance to hydrolysis and stretching. A material that combines the best characteristics is polyurethane. Currently, a stiffener is manufactured, for example, from a TDI-polyether Adiprene LI67, with 95 Shore A hardness. For a service life of 20 to 30 years, the maximum temperature of resistance to hydrolysis of this material is 50 ° C.

Classically manufactured stiffeners can reach several meters in length, thicknesses greater than 200 mm for a weight that can exceed 2 tons. To limit the volume occupied and the weight of the stiffeners, polyurethanes are chosen with relatively high hardnesses, typically above 90 Shore A.

In this range of hardness, the processability of polyurethane increases with hardness. In fact, the more the polyurethane hardness increases, the more the gelation time (fpot life ”in English) of the mixture prepared from a prepolymer based on diisocyanate and a chain extender such as polyamines or polyalcohols is short, which it requires the use of high flow rate casting machines, especially when it comes to molding large parts.

An object of the invention is to propose a stiffener that exhibits an improved resistance to aging by at least 10 ° C compared to the stiffener of the prior art, while ensuring good homogeneity of mechanical properties.

Another objective of the invention is to allow the manufacture of a stiffener that has a higher hardness in relation to the stiffener of the prior art, of 60 Shore D, for example, while ensuring a good homogeneity of the mechanical properties.

The third advantage is to allow the manufacture of a stiffener whose processability is improved over that of the prior art stiffener.

Surprisingly, it was found that a polyurethane elastomer prepared from a 5-diphenylmethane diisocyanate (MDI) prepolymer and a chain extender chosen from among the polyamines could be used to manufacture a stiffener. The stiffener thus manufactured then exhibits even greater resistance to aging compared to the known stiffener as well as improved processability. This improvement in processability 10 allows for the realization of a stiffener of higher hardness.

According to a specific mode of the invention, the polyurethane elastomer is prepared from a diphenylmethane diisocyanate (MDI) prepolymer and a methylene dianiline salt. This embodiment is particularly advantageous for cold forming (“cold casf 15 according to English terminology) of the stiffener. Cold molding the stiffener is particularly advantageous in that it does not require a very complex apparatus.

The description that follows will present in detail the ways of carrying out the invention and other advantages in reference to the attached drawing:

Figure 1 is a cross-sectional view of a flexible conduit provided with a stiffener according to the invention.

Figure 1 schematically shows a flexible conduit (10) provided with a stiffener (12). The flexible conduit is engaged through the guide tube (14) of the surface installation (not shown). The stiffener is placed at the level of the duct in such a way that when connecting the flexible duct to the surface installation, the stiffener is at the level of the nozzle of the guide tube, thus protecting the flexible duct from any deterioration during the movements of the vessel. The stiffener is then secured by a clamping collar (not shown) or any other known means around the end of the guide tube.

According to the invention, the stiffener is manufactured from a new polyurethane composition. The polyurethane used to manufacture the stiffener is obtained from a diphenylmethane diisocyanate prepolymer composition (MDI prepolymer). This prepolymer is then cross-linked with a polyamine to form the polyurethane elastomer composition capable of being shaped to make the stiffener.

The polyurethane elastomer is thus prepared according to a two-step process. In the first instance, an intermediate prepolymer is prepared by condensing the alcohol functions of a polyol on the isocyanate functions of a polyisocyanate. In a second step, the prepolymer and the crosslinking agent are preheated and mixed in a casting machine, then the mixture is injected into a preheated mold of the stiffener, and finally this mold is kept at a temperature in an oven during the duration of the crosslinking.

This manufacturing process makes it easier to control the characteristics of the final material, which has an advantage when it comes to modeling parts requiring large amounts of material, as is the case with the stiffener.

According to a first step, an intermediate prepolymer of diphenylmethane diisocyanate (MDI prepolymer) is synthesized.

The MDI prepolymer is obtained by reacting an MDI diisocyanate with a high molecular weight polyol comprised, for example, between 250 and 10,000 g.mof ¹ at a temperature between 30 and 150 ° C. The relationship between the number of N = CO functions and the number of OH functions in the reaction mixture can be between 1.5 and 20. The reaction temperature is, for example, between 30 and 150 ° C.

The MDI diisocyanate used for the preparation of the MDI prepolymer is selected from 2.4 'diphenylmethane diisocyanate and 4.4' diphenylmethane diisocyanate or 2.2 'diphenylmethane diisocyanate.

Alternatively from 0 to 20% by weight of an aliphatic diisocyanate can be added to the MDI prepolymer composition. The aliphatic diisocyanate is then chosen from the group consisting of 1,1'methylene-bis (4-isocyanatocyclohexane), 1,4-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), 1,3-xylene diisocyanate , 10 hexamethylene diisocyanate and 1,1,4,4-tetramethylxylene diisocyanate or a mixture of one of these compounds.

Preferably, the high molecular weight polyol is chosen from the group of polyether glycol and polyester glycol.

Following the text, the term "diphenylmethane diisocyanate prepolymer composition" is defined as a composition containing at least 80% diphenylmethane diisocyanate prepolymer obtained by reacting at least one polyol and a diisocyanate monomer and may comprise, in addition to in addition, an amount of free MDI monomer or other solvent or plasticizer.

According to a second step, the MDI prepolymer composition is then reacted with a crosslinking agent in a ratio of the stoichiometric order selected between the polyamines and preferably the aromatic polyamines. The relationship between the number of total N = CO functions in the MDI prepolymer composition and the number of NH ₂ functions in the reaction mixture is roughly in the order of stoichiometry. For example, it can be between 0.7 and 1.2.

Preferably, polyamines are chosen from aromatic polyamines. For example, the polyamine can be 4,4'methylene-bis (2-chloroaniline), 3,5-diamino-4 isobutyl ester chlorobenzoic acid or 4,4'-methylene-bis (3-chloro-2, 6-diethylaniline).

The mixture consisting of the prepolymer composition and the crosslinking agent is injected into a preheated mold having the typical conical shape of a stiffener. This mold is kept at an oven temperature for the duration of the crosslinking and finally the stiffener is demoulded.

Patent application EP 1950234 typically describes a new polyurethane elastomer that can be used to manufacture a stiffener according to the first embodiment of the invention.

EP 19550234 describes, in effect, a polyurethane elastomer obtained from a prepolymer comprising diphenylmethane 2,4 'diisocyanate prepared according to a process comprising the following steps:

(a) reacting diphenylmethane diisocyanate (MDI) comprising more than 80% diphenylmethane 2,4'-diisocyanate with high molecular weight polyol selected from the group of polyalkylene ether polyols having a molecular weight comprised between 250 and 10000 g. mof ¹ at a temperature between 30 and 150 ° C for a time sufficient to form the 2,4 'MDI prepolymer and to react the OH functions of the polyol with a relationship between the NCO functions and the OH functions between 1, 5: 1 and 20: l.

(b) adding to the 2,4'MDI prepolymer an aliphatic diisocyanate chosen from ο Ι, Γ-methylene-bis (4-isocyanatocyclohexane), the

1.4- cyclohexane diisocyanate, isophorone diisocyanate (IPDI), xylene 1,3diisocyanate, hexamethylene diisocyanate and diisocyanate of

1.1.4.4- tetramethylxylene or a mixture of one of these compounds.

(c) add a necessary amount of aliphatic and / or aromatic di- or polyamine by which the constituents will react so that the equivalent relationship between the NCO groups and the sum of the free NCO groups is between 0.8: 1 and 1 , 2: 1.

The synthesis method described in EP1950234 is a possible way of obtaining a polyurethane elastomer by forming a 2.4 'MDI prepolymer composition, crosslinked by an aliphatic or aromatic polyamine and hot molded to make a stiffener.

Whereas, previously, the crosslinking of an MDI prepolymer with a polyamine was removed due to its very high reactivity with respect to MDIs, patent application EP 1950234 describes a new route of synthesis of polyurethane elastomers by reaction of a composition containing an MDI prepolymer and a polyamine where the reaction parameters are controllable.

Stiffeners prepared from a polyurethane elastomer synthesized by reacting a composition comprising a prepolymer of MDI and a polyamine have better characteristics of resistance to hydrolysis and a better fatigue behavior than stiffeners made from the polyurethane elastomers of the prior art, while preserving homogeneous mechanical properties in areas of great thickness, typically 100 mm to 500 mm. In addition, it remains possible, always maintaining the homogeneity of mechanical properties, to obtain hardeners of greater hardness. Finally, a great advantage is the better processability of the polyurethane as the formulations based on MDI prepolymer and a polyamine allow, in the course of molding, to ensure a cohesion between the molded part already hardened and the rest of the formulation that still it is not hardened.

The characteristics of the material thus obtained make it possible to achieve a hardness between 50 Shore D to 70 Shore D while ensuring homogeneous properties within the material. Hardness measurements are carried out in accordance with ISO 868 or ASTM d2240 ... The material obtained also has a hydrolysis resistance of up to 60 ° C for 30 years, or even 70 ° C for shorter periods, a resistance to fatigue increased by a factor of 2 to 10 according to the conditions of use. Measurements of resistance to hydrolysis are performed by tensile tests according to the ASTM D638 standard on specimens having been subjected to accelerated aging in water, and by extrapolation by Arrhenius law.

A second particular embodiment of the invention will now be described. In this particular embodiment of the invention, the diisocyanate prepolymer is cross-linked with a particular family of amines whose reactivated amine functions are blocked to decrease its reactivity with respect to the MDI prepolymer.

The polyurethane elastomer used to manufacture the stiffener is obtained from a diphenylmethane diisocyanate prepolymer composition (MDI prepolymer) which is then cross-linked with a methylene dianiline salt (MDA) complex to form the polyurethane elastomer composition. able to be cold formed to manufacture the stiffener. By cold forming it is necessary to understand that the filling of the mold can be done without having to preheat the mold or even the reagents (except to ensure degassing) and that the crosslinking reaction does not operate when filling the mold. This allows a slow and controlled filling of the mold, thus avoiding the formation of bubbles, the crosslinking being operated in a second time when the temperature introduced of the material introduced in the mold of the form of the stiffener.

Methylene dianiline salt (MDA) is a polyamine whose amine functions are blocked in order to decrease the reactivity of the amine with respect to the MDI prepolymer at the time of crosslinking the MDI prepolymer composition and thus being able to proceed, with advantage, to molding (cold cast in English terminology). During the cold molding phase, the amine functions of the MDA salt will be released by a controlled rise in temperature to react with the MDI prepolymer composition. Progressive release of the amine functions of the MDA salt complex makes it possible to decrease the reactivity of the crosslinking agent and to advantageously perform a cold molding of the stiffener.

The polyurethane elastomer is prepared according to a three-step process. In the first instance, an intermediate prepolymer composition is prepared by condensing the alcohol functions of a polyol on the isocyanate functions of a polyisocyanate as previously described for the first embodiment of the invention.

In a second step, the MDI prepolymer and the MDA salt are mixed preheated around 70 ° C to ensure degassing of the mixture.

The methylene dianiline (MDA) salt is advantageously the tris- (4,4'-diaminodiphenylmethane) complex, NaCl, obtained between methylene dianiline (MDA) and the sodium chloride salt. This salt can optionally comprise a plasticizer. For example, it is proposed under the brands CAYTUR 31 ™ and CAYTUR 31-DA ™.

The mixture is then injected into a form of a stiffener.

In a third stage, the mold that may have been previously preheated is introduced into a stove whose temperature rise is controlled. During this last stage, the temperature rise profile of the furnace is adjusted to progressively release the amine functions of the MDA salt and crosslink the MDI prepolymer.

In this particular embodiment, the reaction time that effects the formation of the polyurethane elastomer is longer thanks to the controlled reactivity of the selected crosslinking agent. Thus, it is not necessary to use casting machines with a high flow rate. In addition, the stiffener made from polyurethane elastomer obtained from an MDI prepolymer cross-linked with methylene dianiline salt (MDA) has mechanical characteristics comparable to those obtained with the stiffener obtained according to the first embodiment of the invention .

Patent application W02009108510 typically describes a new polyurethane elastomer that can be used to manufacture a stiffener by the cold molding technique according to the second embodiment of the invention. Also, the teachings of patent application W02009108510 are incorporated by reference to the patent application.

W02009108510 describes a composition of polyurethane elastomer obtained by reacting a prepolymer of MDI and methylene dianiline complexed with a sodium chloride salt whose mixture is stable over time for several days at the degassing temperature of 70 ° C.

This mixture is then introduced into a stiffener mold and heated to a crosslinking temperature to be determined between 115 and 130 ° C to release the blocked amines from the MDA complex and initiate the crosslinking reaction of the MDI prepolymer composition.

The crosslinking reaction takes place under almost stoichiometric conditions. Stoichiometry is determined by the relationship between the number of total N = CO functions in the MDI prepolymer composition and the total number of NH2 functions released at the crosslinking temperature of the MDI prepolymer. This ratio is easily determined and can be between 0.7 and 1.2, for example.

The stiffener thus obtained has improved properties similarly to that described for the first embodiment of the invention.

Claims (9)

1. Stiffener for flexible duct, characterized by the fact that it is manufactured from polyurethane, said polyurethane is obtained by reacting in a ratio between 0.7 and 1.2 a composition comprising at least 80% of a diisocyanate prepolymer of diphenylmethane (MDI) and a polyamine. 2. Stiffener according to claim 1, characterized in that the diphenylmethane diisocyanate prepolymer composition furthermore contains up to 20% by weight of an aliphatic diisocyanate chosen from 1,1'-methylene-bis (4-isocyanatocycle -hexane), cyclohexane 1,4diisocyanate, isophorone diisocyanate (IPDI), xylene 1,3diisocyanate, hexamethylene diisocyanate and tetramethylxylene 1,1,4,4-diisocyanate or a mixture of one of these compounds. 3. Stiffener according to one of the preceding claims, characterized in that the polyamine is chosen from 4,4'methylene-bis (2-chloroaniline), 3,5-diamino-4-isobutyl ester chlorobenzoic acid and 4.4 ' -methylene-bis (3-chloro-2,6-diethylaniline) 4. Stiffener according to claim 1 or 2, characterized by the fact that the polyamine is the complex of tris (4,4'-diaminodiphenylmethane), NaCl and the fact that the stiffener is cold molded. A hardener according to one of the preceding claims, characterized in that the diphenylmethane diisocyanate prepolymer is synthesized by reacting a diphenylmethane diisocyanate and a polyol having a molecular weight between 250 and 10000 g.mol ' ¹ chosen from the polyester glycol and polyether glycol group and where the relationship between the function number N = CO and the function number OH in the reaction mixture is between 1.5 and 20. 6. Stiffener according to claim 5, characterized by the fact that polyol is chosen from the family of polyethers glycol. 7. Stiffener according to claim 1, characterized in that the diphenylmethane diisocyanate is diphenylmethane 2,4'-diisocyanate. 8. Stiffener according to claim 3, characterized by the fact that it is hot molded. A stiffener according to one of the preceding claims, characterized in that the stiffness of the stiffener is greater than or equal to 50 Shore D with a hydrolysis resistance of at least 50 ° C over a period of 20 years.