Wrapped radio opaque yarn

Description

[0001] This invention relates to radio opaque yarn such as that used in the manufacture of surgical swabs and dressings.

[0002] Radio opaque filaments, resp. fibres are disclosed in our European patent application No. 83304777.2 (EP-A-101650). These fibres contain a high proportion of barium sulphate in order to provide the required degree of X-ray opacity. Such highly filled fibres tend to stretch due to fracture of the constituent filaments. Moreover the fractured filaments tend to run causing aggregations which may snarl-up during weaving.

[0003] According to the present invention a radio opaque yarn comprises a bundle of filled filaments containing not less than 54% w/w of barium sulphate, characterised in that the bundle is bound with up to 20% w/w of a substantially unfilled filament having a diameter of 0.05 of the diameter of the bundle of filled filaments, wherein the yarn comprises 2 to 8 turns per cm of the binding filament.

[0004] Conventional wrapped yarns contain approximately 50% by weight of binding filament. The present invention employs a higher proportion of filled filaments. This is important in the production of radio opaque yarns to optimise the opacity of the product. The unfilled, binding filament may have a higher modulus and tensile strength than the filled filaments, increasing the strength and durability of the yarn. Furthermore the binding prevents running of any fractured filled filaments. This particularly facilitates narrow weaving or knitting where control of yarn tension is important. The binding filaments may be monofilament or multifilament.

[0005] Preferred yarns in accordance with this invention comprise less than 5% w/w of binding filament.

[0006] The binding filament may be wound at a preferred rate of 4 to 6 turns per cm, more preferably 4 turns per cm. Yarn having less than 2 turns per cm of wrapping filament tend to fragment during weaving, whereas yarn having more than 8 turns per cm is brittle and liable to break during cloth processing.

[0007] The binding filament preferably comprises a polyester although alternative materials which form filaments having a high modulus and tensile strength may be employed.

[0008] The filled filament preferably comprises polypropylene. Polyester filaments have also been found to be applicable. A maximum of 80% w/w of barium sulphate has been found to be appropriate although a maximum of 70% w/w may be preferred. A coupling agent may be employed, for example an alkanoyl triisostearoyl titanate or other of the coupling agents disclosed in European patent application No. 83304777.2.

[0009] One to five binding filaments may be employed although use of a single filament is preferred because wrapping with a plurality of filaments has not been found to confer any additional advantages. The binding filaments may be textured, bulked, crimped or otherwise treated both to impart extensibility to the yarn and to improve the ability of the yarn to withstand wet and dry fabric finishing operations.

[0010] The invention is further described by means of examples and not in any limitative sense.

[0011] A bundle of twenty filaments composed of polypropylene (melt flow index=12, 29.5% w/w), barium sulphate (particle size 0.5 µm, 70% w/w) and a coupling agent isopropyl triisostearoyl titanate (0.5% w/w) and a pigment (Cobalt Blue Med) having a weight of not less than 3000 decitex was wrapped with 4 turns per cm of a flat polyester fibre (24 filament, 74 decitex, no added lubricant). The resultant yarn contained 68% w/w of barium sulphate and satisfied both -the British Phar- macopea Index test (reference SDM XVII) and the U.S. pharmaceutical X-ray opacity requirements. The yarn was found to have a minimum breaking load greater than 500 cN and a breaking extension not less than 100% but not greater than 300%. The yarn could be woven without difficulty.

Claims

1. A radio opaque yarn comprising a bundle of filled filaments containing not less than 54% w/w of barium sulphate characterised in that the bundle is bound with up to 20% w/w of a substantially unfilled filament having a diameter of 0.05 of the diameter bundle of filled filaments wherein the yarn comprises 2 to 8 turns per cm of the binding filament.

2. A radio opaque yarn as claimed in claim 1, characterised in that the binding filament comprises less than 5% w/w of the yarn.

3. A radio opaque yarn as claimed in claim 1, characterised in that the yarn comprises 4 to 6 turns per cm of binding filament.

4. A radio opaque yarn as claimed in any preceding claim, characterised in that the binding filament comprises polyester.

5. A radio opaque yarn as claimed in any preceding claim characterised in that the filled filament comprises polypropylene or polyester.

6. A radio opaque yarn as claimed in claim 5, characterised in that the filled filament comprises 54% to 80% w/w of barium sulphate.

7. A radio opaque yarn as claimed in claim 5 characterised in that the filled filament comprises 54% to 70% w/w of barium sulphate.

8. A radio opaque yarn as claimed in any of claims 1 to 7 characterised in that the yarn includes an alkanoyl triisostearoyl titanate coupling agent.

Ansprüche

1. Röntgenoskopisches kontrastierendes Garn mit einem Bündel von mit Füllstoff versehenen Fäden, die zumindest 54 Gewichtsprozent Bariumsulfat enthalten, dadurch gekennzeichnet, daß das Bündel mit einem bis zu 20 Gewichtsprozent ausmachenden, im wesentlichen füllstofffreien Faden gebunden ist, dessen Durchmesser 0,05 des Durchmessers des Bündels der mit Füllstoff versehenen Fäden beträgt, wobei das Garn pro Zentimeter 2 bis 8 Windungen des bindenden Fadens aufweist.

2. Röntgenoskopisches kontrastierendes Garn nach Anspruch 1, dadurch gekennzeichnet, daß der bindende Faden weniger als 5 Gewichtsprozent des Garns ausmacht.

3. Röntgenoskopisches kontrastierendes Garn nach Anspruch 1, dadurch gekennzeichnet, daß das Garn pro Zentimeter 4 bis 6 Windungen des bindenden Fadens aufweist.

4. Röntgenoskopisches kontrastierendes Garn nach einem vorausgehenden Anspruch, dadurch gekennzeichnet, daß der bindende Faden Polyester aufweist.

5. Röntgenoskopisches kontrastierendes Garn nach irgendeinem vorausgehenden Anspruch, dadurch gekennzeichnet, daß der mit Füllstoff versehen Faden Polypropylen oder Polyester aufweist.

6. Röntgenoskopisches konstrastierendes Garn nach Anspruch 5, dadurch gekennzeichnet, daß der mit Füllstoff versehene Faden 54 bis 80 Gewichtsprozent Bariumsulfat aufweist.

7. Röntgenoskopisches kontrastierendes Garn nach Anspruch 5, dadurch gekennzeichnet, daß der mit Füllstoff versehene Faden 54 bis 70 Gewichtsprozent Bariumsulfat aufweist.

8. Röntgenoskopisches kontrastierendes Garn nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß das Garn als Kupplungsmittel Alkanoyl-triisostearoyl-titanat enthält.

Revendications

1. Fil opaque à là radio comprenant un paquet de filaments chargés ne contenant pas moins que 54% une contenant pas moins que 54% en poids de sulfate de baryum, caractérisé par le fait que le paquet est lié avec jusqu'à 20% en poids d'un filament sensiblement non chargé, ayant un diamètre de 0,05 fois le diamètre du paquet de filaments chargés, où le fil comprend 2 à 8 tours par cm de filament de liage.

2. Fil opaque à la radio selon la revendication 1, caractérisé par le fait que le filament de liage comprend moins de 5% en poids du fil.

3. Fil opaque à la radio selon la revendication 1, caractérisé par le fait que le fil comprend 4 à 6 tours par cm de filament de liage.

4. Fil opaque à la radio selon l'une des revendications précédentes, caractérisé par le fait que le filament de liage comprend du polyester.

5. Fil opaque à la radio selon l'une des revendications précédentes, caractérisé par le fait que le filament chargé comprend du polypropylène ou du polyester.

6. Fil opaque à la radio selon la revendication 5 caractérisé par le fait que le filament chargé comprend 54 à 80% en poids de sulfate de baryum.

7. Fil opaque à la radio selon la revendication 5, caractérisé par le fait que le filament chargé comprend 54 à 70% en poids de sulfate de baryum.

8. Fil opaque à la radio selon l'une des revendications 1 à 7, caractérisé par le fait que le fil inclut un agent de couplage titanate d'alcanoyl-triisos- téaroyle.