SK5202002A3 - Extrusible thermoplastic material and optical fibre micromodule made from same - Google Patents

Abstract

The invention concerns a material for forming thin films. It consists of a composition containing an olefin polymer and a filler ratio ranging between 25 and 65 wt.% of the composition, said material in undivided state having a tensile strength ranging between 6 and 20 Mpa and an elongation at break ranging between 50 and 300 %.

Description

Technique Area

The present invention relates to an extrudable material which makes it possible to produce thin coatings based on an olefin polymer. This material has a particularly important use, albeit not exclusively, in the manufacture of a cable embedded micro-module of optical fibers similar to that described in EP-A-O-468 878 to which it refers.

BACKGROUND OF THE INVENTION

In some applications, in particular in the production of micromodules of a bundle of coated fiber optics in contact with each other, sealed by an impermeable gel in a holding extruded package, it is necessary to meet conditions that are somewhat contradictory. For example, it is often sought, especially in the case of micromodule production at the same time:

- ability to compress to thin coatings - if possible up to 0,1 mm,

- compatibility of the material with gels which are usually impermeable,

- sufficient strength of the material produced in the form of thin coatings to allow handling during subsequent operations without risk of tearing,

- the inability to adhere to the fibers of the micromodule during heating, due to the introduction of the outer packaging onto the thermoplastic material, which is necessary when the outer packaging onto the thermoplastic material is introduced,

- maintaining the correct cylindricality during micromodule production and cable assembly,

- limited shrinkage during extrusion of the micromodule housing and during cooling to avoid tensions on optical fibers,

- simple dyeing of the material to allow identification of micromodules,

- limited elongation allowing easy insulation of the micromodules to prepare a fiber-wiring terminal, and

Finally, high resistance to the chemicals used during the operating steps on the cables, for example to the cleaning solvent.

In the case of fiber optic cable manufacturing, some of the above characteristics are essential, particularly mechanical strength, including during thermal aging, and compatibility with an impermeable gel and cleaning solvent that has been used to remove gel and dirt before plugging the fiber optic terminals into the connector. However, mechanical strength is unsatisfactory for convenience of use, as a solid sheath coating with high tensile strength and high elongation before rupture hinders the stripping of the micromodule to release the fiber ends.

It is already known (GB-A-2110696) an electrical insulating material based on a mixture of at least partially crosslinked polymers, comprising in particular an EVA (ethyl acetate) co-polymer with at least 40% vinyl acetate, with sufficient inorganic additives, to form a refractory material. The crosslinking is intended to increase the additive content.

It is an object of the invention to provide a material that is extrudable to a thin coating and represents a compromise between the different results to achieve it.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides an extrudable material that allows the formation of thin coatings based on at least one olefin polymer and which is made from a composition comprising at least one thermoplastic olefin polymer practically uncrosslinked with an additive content in the range of 25 to 65% by weight. based on the mixture, wherein the material in the non-rusted state has a tensile strength between 6 and 20 M Pa and an elongation at break of between 50 and 300%.

By virtually uncrosslinked is meant a commercially available polymer which has substantially no degree of crosslinking and does not contain crosslinking agents such as peroxides, except for trace amounts.

Due to the absence of crosslinking, we avoid the presence of very unsuitable "gels" during extrusion onto thin coatings, thereby reducing shrinkage after compression, which causes stresses on the fibers.

A material hardness in the range of 35-55D is preferred.

The choice of material hardness in Shore D of more than 35 allows, when using the material to make the micromodule housing, to ensure satisfactory cylindricality and to avoid the "straw" effect that results from the sharp bending during bending needed in joining.

Due to the limited elongation mainly due to the presence of additives, stripping is sufficient without the use of special devices. The minimum characteristics listed below, in particular tensile strength and elongation at break, prevent excessive material brittleness during handling. These minimum values allow handling during cable manufacturing or splicing without a high risk of damage.

The minimum additive content of the above makes it possible to reduce the dilatation and shrinkage of the material during the temperature change that occurs in the cable production. The presence of sufficient additive content makes it possible to avoid the risk of the micro-modules sticking to each other, on the coated fibers or on the outer packaging.

In general, the additives will be inorganic. In particular, it is possible to use alumina (hydrated or not), chalk, kaolin, talc, silica, magnesium hydroxide or mixtures thereof. All of these additives reduce ductility and dilatation or shrinkage during temperature changes. In addition, they increase thermal resistance and heat capacity. The anticipated maximum content of the above additives allows the viscosity to be maintained at a level compatible with the extrusion of thin coatings.

The olefinic polymers that can be used are approximately the same as are currently and currently used. In particular, the following products may be cited:

- PE: polyethylene

- PP: polypropylene

- EPR: Ethyl propylenes of rubber

- EPDM: ethylene propylenediene monomer

- EVA: ethylene acetate lower alkyl copolymers (especially vinyl acetate)

- EBA: ethylene acrylate lower alkyl copolymers

- for EEA: ethylene ethyl acrylate

- for EMA: ethylene methyl acrylate

- VLDE: very low density polyethylene

polymers grafted with acrylic acid or maleic anhydride

- PVC: polyvinyl chloride

-4- mixtures and copolymers thereof.

The different polymers are not equally equivalent to each other. Often a mixture of olefin polymers is used, one of which is PE or PP and the other selected from the other polymers listed above.

If the second polymer is EVA, a compound having no more than 30% vinyl acetate co-monomer is used. EBA, EEA or EMA have properties closer to EVA. EPR and EPDM will be used with a high enough ethylene content to avoid having properties that are close to those of the elastomer.

When using a polymer composed on the one hand of PE or PP and on the other hand of an EVA copolymer, a compound having from 40% to 80% EVA is suitably used.

In general, the printable material will additionally contain a low lubricant content that does not exceed several weight percent, such as aliphatic oils or phthalates (e.g., dioctyl or didecyl phthalate), adipates, trimellitates, and the like.

Protective products against heat or ultraviolet radiation are incorporated when precautions are taken against sunlight or exposure.

In some cases, one or more silanes or aminosilanes are added, such as:

- vinyltrimethoxysilane

- aminopropylsilane

- aminotrimethoxysilane.

When trialkoxysilane is used, a compound of less than 5 carbon atoms is suitable.

Silanes strengthen the bond between the additives and the polymers.

The absence of crosslinking agents does not jeopardize that the silanes will form a network. Moreover, in the case of using the material for the production of the optical fiber housing, the formation of the mesh will not be possible because the required temperatures for its formation will not be reached at extrusion.

The invention also provides an optical fiber micromodule comprised of a fiber optic bundle and a sheath that envelops the bundle with a thin coating of an extrudable material, wherein the material comprises a thermoplastic olefin polymer and additives

% In the range of 25 to 65 wt. based on the mixture, wherein the material in the non-rusted state has a tensile strength of 6 to 20 MPa and an elongation of between 50 and 300%.

By way of example, we will now present the properties of many of the materials of the invention and at the same time a comparison with the standard (comparative) material which has hitherto been traditionally used to manufacture a micromodule housing.

Overview of the figures in the drawing

The figure shows the micromodule in a deformed state, which is obtained by pressing the outer shell of the micromodule.

DETAILED DESCRIPTION OF THE INVENTION

The micromodule consists of a plurality of optical fibers 10 individually coated and embedded in the housing 12, which must be easily torn to allow stripping of the fiber ends for wiring. This housing 12 is generally made by extruding onto a bundle of optical fibers 10 as they are pulled. The sleeve changes to approximately a circular shape when the fiber bundle itself also exhibits a circle whose shape does not differ greatly from the defined circle. The sleeve envelops and presses the fibers. Inside the cable, the pressure of the micromodule between each other can deform their cross-section and bring them into the shape shown in the figure.

The comparative material is composed of polyethylene with a nominal density of 0.92 and a melt flow index of 0.3 g / 10 min at 190 ° C and a pressure of 21.6 N. This material was used to make a micromodule powder by extruding it onto a bundle of four optical fibers. The housing 12 produced has a diameter of 1 mm and a thickness of 0.12 mm. The embossing is carried out without problems and the sleeve obtained is circular. However, in the manufacture of a sheath by extruding a polyethylene-based outer sheath, the necessary heat to compress the sheath deforms the micromodules and the sheaths tend to stick to each other and to the outer sheath, requiring particular attention, for example placing one or more substances between the micromodules and the sheath.

These difficulties are overcome by using the material of the invention in practice.

-6Example 1

The mixture with the weight composition below was prepared in a mixer:

50 parts of polyethylene having a density of 0.92 and having a melt index at 190 ° C and a pressure of 21.6 N of 1.8 g / 10 min.

50 parts of an EVA copolymer containing 18% vinyl acetate

-130 parts alumina hydrate

- 5 parts lubricant (paraffin oil)

- 5 parts of additives (antioxidants, silane, lubricant).

The ingredients were mixed for 10 minutes at a temperature of up to 160 ° C.

After calendering on a rotary roll, the material was sheared, then pressed at 180 ° C under pressure into plate molds on which characteristic material tests could be carried out.

The mechanical characteristics obtained during plate testing are as follows:

- tensile strength: 11.4 MPa

- elongation at break: 125%

- hardness = 45 Shore D.

The mixture was used to prepare the micromodule. For this, the mixture was granulated, fed into an extruder with a diameter of 45 mm and a length of 24 x diameter.

The extrusion operating temperatures range from 130 to 160 ° C from the hopper to the extrusion head.

Two operations were performed to characterize the obtained housing.

The first was at molding at a speed of 100 m / min, to obtain a tube with a diameter of 0.90 mm and a radial thickness of 0.12 mm.

For the second, the introduction into the mold was identical and, with a small difference in extrusion, where four colored optical fibers were inserted over the extruder face and where a simultaneously impermeable gel was sprayed to form a module which, after cooling the extruded material, was trapped in the tank. freely winds on a plane.

The measured characteristics of the housing are as follows.

Module without leakproof gel Module with gel Original characteristics RT = 4.5 N AR = 138% RT = 4.6 N AR = 112% Winding on template 6D right right After 10 days at 70 ° C VarRT = 19% VarAR = 15% VarRT = 13% VarAR = 13% After 10 days at 70 ° C + 42 days at 80 ° C VarRT = 17% VarAR = 20% VarRT = 9% VarAR = 11%

RT = tensile strength,

AR = tear elongation (elongation)

Var = change

These results show, on the one hand, heat resistance and, on the other hand, compatibility with the filler of the sheath material of the present invention.

Example 2

The material mixture is identical to Example 1, except that the alumina hydrate additive is replaced by a calcium carbonate additive. The mixture was prepared under the same conditions and extruded at a rate of 100 / minute, a micromodule having a diameter of 0.85 mm and a thickness of 0.11 mm. In particular, the characteristics shown below show how modules having good chemical resistance (chemical resistance) are obtained from such a mixture despite the thin thickness of the module housing.

Original characteristics RT = 4.5 N AR = 138% After an hour in ethanol at 20 ° C VarRT = 1% After an hour in isopropanol at 20 ° C VarRT = 5% VarAR = 3%

Example 3

Here, an identical mixture is carried out as in Example 1, except that the alumina-based additive is replaced by a kaolin-based additive,

-8a at a reduced concentration to 65 parts. The paraffin lubricant is replaced by an isononyl adipate type oil.

The various ingredients are introduced into the interior of the mixer, mixed at up to about 160 ° C and then granulated. The material characteristics measured on the boards are as follows:

Originally mechanical characteristics Tensile strength Elongation at break RT = 10.5 MPa AR = 157% Aging for 10 days at 70 ° C VarRT = +1% VarAR = -12% Aging for 42 days at 80 ° C VarRT = + 7% VarAR = -18% Macroplast CF 300 gel compatibility for 10 days at 70 ° C VarRT = -15% Weight change VarAR = -17% = 7% Stored in water vapor for 42 days at 20 ° C and 93% humidity VarRT = -4% VarAR = +2% Immersion in kerdane for 24 hours at 20 ° C VarRT = -25% VarAR = -10% Immersion in ethanol for 1 h at 20 ° C VarRT = -4% VarAR = -10% Immersion in isopropanol for 1 h at 20 ° C VarRT = -6% VarAR = -4% Immersion in isopropanol for 1 h at 20 ° C VarRT = -4% VarAR = -10% hardness 45 Shore D

From this mixture, it is made under the same conditions as the micromodule of four optical fibers passing through the case with a thickness of 0.11 mm and a diameter of 0.85 mm. The impermeable gel is Macroplast CF 300 from Henkel.

The measured characteristics on the module are as follows:

Originally mechanical characteristics (MC) RT = 2.4 N AR = 105% MC mixtures after 10 days at 70 ° C VarRT = 5% VarAR = 4% MC changes after 10 days at 70 ° C in Macroplast CF 300 VarRT = 0 VarAR = 6% MC changes after 42 days at 80 ° C VarRT = +2% VarAR = 5% MC changes after 10 days at 70 ° C in CF 300, and 42 days at 80 ° C VarRT = -20% VarAR = -6% MC changes after 42 days at 40 ° C and 93% humidity VarRT = 5.4% VarAR = 0% MC changes after 24 h in kerdan VarRT = 11% VarAR = 25% Changes after 24 h in ethanol VarRT = 8% VarAR = 12% Changes after 24 h in isopropanol VarRT = 4% VarAR = 13%

Claims (10)

PATENT CLAIMS An extrudable material which makes it possible to form thin coatings based on at least one olefin polymer, characterized in that it is made from a composition comprising at least one thermoplastic olefin polymer practically uncrosslinked with an additive content in the range of 25 to 65% by weight. based on the composition, wherein the material in the non-rusted state has a tensile strength in the range of 6 to 60 MPa and an elongation at break in the range of 50 to 300%. Material according to claim 1, characterized in that it has a Shore D hardness in the range of 35 to 55. Material according to claim 1 or 2, characterized in that the polymer is selected from the group consisting of: - PE: polyethylene - PP: polypropylene - EPR: Ethyl propylenes of rubber - EPDM: ethylene propylenediene monomer - EVA: ethylene acetate lower alkyl copolymers (especially vinyl acetate) - EBA: ethylene acrylate lower alkyl copolymers - for EEA: ethylene ethyl acrylate - for EMA: ethylene methyl acrylate - VLDE: very low density polyethylene polymers grafted with acrylic acid or maleic anhydride - PVC: polyvinyl chloride - mixtures and copolymers thereof. Material according to claim 1, 2 or 3, characterized in that the additives are selected from the group consisting of alumina (hydrated or not), chalk, kaolin, talc, silica, magnesium hydroxide and mixtures thereof. -11 Material according to any one of the preceding claims, characterized in that the polymer is a blend of olefinic polymers, one of which is PE or PP and the other selected from EVA with at most 30% vinyl acetate, EBA, EEA or EMA comonomer. contain lubricants and additives. Material according to any one of the preceding claims, characterized in that, in addition to lubricants and other non-netting additives, it comprises: 50 parts of polyethylene having a density of 0.92 and a melt index at 190 ° C and pressure 21.6 N 1.8 g / 10 min 50 parts of an EVA copolymer containing 18% vinyl acetate -130 parts alumina hydrate. Material according to any one of claims 1 to 4, characterized in that, in addition to lubricant and additives, it contains: 50 parts of polyethylene having a density of 0.92 and a melt index at 190 ° C and pressure 21.6 N 1.8 g / 10 min 50 parts of an EVA copolymer containing 18% vinyl acetate -130 parts calcium carbonate. Material according to any one of claims 1 to 4, characterized in that it contains, in addition to lubricants and additives: 50 parts of polyethylene having a density of 0.92 and a melt index at 190 ° C and pressure 21.6 N 1.8 g / 10 min 50 parts of an EVA copolymer containing 18% vinyl acetate - 65 parts kaolin. Material according to any one of claims 1 to 7, characterized in that it contains one but more silanes and aminosilanes. 10. An optical fiber micromodule comprised of an optical fiber bundle and a bundle enveloping the bundle in the form of a thin coating of extrudable material, characterized in that the sleeve is composed of a mixture % Of a thermoplastic olefin polymer having a content of 25 to 65 wt. The non-rusted material has a tensile strength of 6 to 60 MPa and an elongation at break of 50 to 300%.