EP1584709A1

EP1584709A1 - Antibacterial yarn for carpets

Info

Publication number: EP1584709A1
Application number: EP05102535A
Authority: EP
Inventors: Paolo Rossi
Original assignee: RADICIFIL SpA
Current assignee: RADICIFIL SpA
Priority date: 2004-03-31
Filing date: 2005-03-31
Publication date: 2005-10-12
Also published as: ITMI20040642A1

Abstract

New yarns are described which contain incorporated therein an antibacterial substance containing silver, and a process for incorporating said substance into the yarn in a stable manner.

The procedure is characterised by adding an antibacterial substance containing silver to the polyamide used in the preparation of the fibre; the mixture thus obtained is then subjected to extrusion and spinning, to form fibres containing the antibacterial incorporated in bulk into the fibre structure; there follow one or more fibre conditioning processes, specifically predisposed to obtain fibres usable for producing carpets and other flooring textiles.

Description

Field of the invention

The present invention relates to the field of carpet yarns. New yarns are described which contain incorporated therein an antibacterial substance containing silver, and a process for incorporating said substance into the yarn in a stable manner.

Prior art

The need for protecting textiles from bacterial contamination has been felt for some time, being of even greater urgency if the textile in question is exposed to contamination and is difficult to clean.
A typical example of said textiles is represented by carpets, fitted carpets, runners, mats and the like. These products are typically exposed to pollutants and bacterial contaminants by contact with shoes, as well as by the accidental spillage of liquid or solid foods. Carpet cleaning systems remove visible dirt and dust, but do little against bacterial contamination; in particular, cleaning systems leave the carpet in a damp condition and bacterial colonies find such conditions ideal for reproducing.
From this the need arises to intervene also with chemical products which prevent bacterial growth. The addition of antibacterial substances to synthetic yarns used for different applications is generally known. In the specific field of carpeting, treating the surface of carpets with antibacterial substances is known, thus obtaining carpets with adsorbed antibacterials. Such a treatment is limited, however, in that the product is easily washed away during cleaning routines; also it is easily transferred to man/animals by contact with the carpet surface and therefore constitutes a potential source of allergies and other skin problems. Adding the antibacterial to adhesives used to fix yarn to the carpet backing is also known: in this case, however, the antibacterial is little effective against contaminations on the external surface of the carpet which are obviously the most frequent.
Processes in which the antibacterial substance is added to the master batch destined for synthetic fibre production are also generally known, thus obtaining fibres containing the antibacterial incorporated into the structure of the fibre; such processes, not developed specifically for the production of carpets, are conditioned by the compatibility of the antibacterial with the master batch used for fibre production and are difficult to control in terms of uniform distribution of the antibacterial; such difficulties are most apparent in the case of polyamide, being typically used in carpet fibres: polyamide fibres contain various acid and basic functional groups which interact, sometimes unexpectedly, with the substances added to the mixture; moreover, in the case of carpets, the yarns undergo particularly high stress levels during the production process: known for example are high speed spinning processes (texturizing) and/or twisting of the fibre with heat setting at 190°C in the presence of O₂ and steam; other processes relate to fixing the fibres to the carpet backing, with the use of adhesives, high temperature, solvents etc. Under all these conditions, the substances contained in the fibre deteriorate easily and the antibacterial activity of the final product is undesirably diminished.
The objective of the present invention is to develop a process for incorporating antibacterial substances into polyamide type fibres, specifically suitable for producing carpets. An easily executed process is particularly desired, which allows an antibacterial to be incorporated in a uniform and stable manner into polyamide fibres destined to undergo the stress characteristic of carpet production. Moreover, it is desired to minimise degradation of the antibacterial in the fibre production step, such as to increase the percentage of antibacterial incorporation, thus reducing losses of said product and rendering the production process more economical.
Finally the availability of a new antibacterial yarn is desired which allows a higher level of asepticism to be maintained, preventing the development of bacterial colonies, odours, stains and the like and avoiding undesirable loss into the environment of chemical substances adsorbed by the yarn.

Summary of the invention

It has now been unexpectedly observed that substances containing silver can be incorporated in a stable manner into yarns which are specifically predisposed for the production of carpets and similar textiles for flooring. Incorporation takes place in a stable, uniform and permanent manner. The process is characterised by adding an antibacterial substance containing silver to the polyamide used in the preparation of the polyamide fibres; the mixture thus obtained is then subjected to extrusion and spinning, to form fibres containing the antibacterial incorporated in bulk into the fibre structure; there follow one or more fibre conditioning processes, specifically predisposed to obtain fibres useful for production of carpets and other flooring textiles. The process of the invention enables a higher level of antibacterial to be incorporated, without significant losses thereof due to the fibre forming and conditioning processes; nor are the undesirable phenomena of antibacterial losses from the final product observed. From the mechanical and aesthetic viewpoint, adding the antibacterial does not lead to any variation in mechanical and aesthetic characteristics of the fibres thus produced.

Description of the figures

Figure 1: Plant schematic for producing the yarn of the invention.
Figure 2: Effectiveness of the antimicrobial Alpha Scan RC5000 in nylon yarn for carpets. X-axis: log of reduction relative to untreated control yarn.
1) Standard d Tex 1250 F 68 Bright - untreated
2) 1250 F 68 Bright + 1.2% Alpha San MB (0.36% RC5K)
3) Yarn twisted and Heat Set Superba (steam 122°C) (1.2% Alpha San MB)
4) Yarn twisted and Heat Set Suessen (Hot air 193°C for 1 min) (1.2% Alpha San MB)
5) Standard Heat Set Suessen Yarn (without Alpha San)

Detailed description of the invention

In the present invention the term antibacterial means in general a substance able to oppose the growth of one or more bacteria, fungi, algae, germs, parasites and all other microorganisms typically connected with textile soiling: typical microorganisms responsible for common contaminations of textiles are Escherichia coli, Staphylococcus aureus, mites and various unicellular organisms. The term "antibacterial substance containing silver" means any product, typically inorganic, with antibacterial action and containing in the molecules themselves one or more atoms of silver or silver ions, or products which contain silver in the dispersed form: this category includes carrier substances which contain metallic silver or its salts or oxides in the dispersed state, for example ion exchange resins, zeolites, polymer matrices, ceramic bases (preferably zirconium phosphate), vitreous compounds, nanoparticulate colloidal dispersions of silver etc. Preferably the antibacterial is incorporated into a polyamide based master batch, and as such added to the polyamide which feeds the extruder; the master batch is added in quantities between e.g. 0.3 and 5%, preferably between 1 and 2% by weight relative to the polyamide which feeds the extruder; the effective quantity of master batch added is, however, broadly variable and depends ultimately on the concentration of antibacterial required in the finished fibre: in general, for a good antibacterial effect, antibacterial concentrations of between 2500 and 5000 ppm in the finished fibre are preferred.
Preferred examples of antibacterial substances are ion exchange resins based on zirconium phosphate which contain silver, commercially available and known as Alpha SAN RC 5000 (Milliken), or the product Ultra Fresh CA-16 (Thomson Research Associated Inc.)
The polyamides useful for the purposes of the invention are those typically used for producing synthetic fibres (nylon) for example PA 6 (NH₂-(CH₂)₅-CO polymer) and PA 66 (NH(CH₂)₆-NHCO-(CH₂)₄-CO polymer). Such fibres are typically continuous fibres and are commonly indicated as BCF fibres (bulked continuous filament). However any type of polyamide fibre, including mixed fibres containing polyamide mixed with other polymers, can be favourably used in the present invention.
Particularly important for the purposes of the invention is that the antibacterial is used as very small particles, typically between 0.01 and 10 microns, preferably between 0.1 and 1 micron.
The process of antibacterial incorporation, which can also take place in parallel with the introduction of other substances into the yarn, is characterised by the following steps:
a) mixing together polyamide and an antibacterial agent containing silver
b) extruding the material thus formed
c) spinning the extruded material, to obtain fibres containing the incorporated antibacterial
d) executing one or more of the following fibre conditioning treatments: drawing, texturizing, interlacing, twisting, heat setting.
The passages a-d are hereinafter discussed in detail with reference to figure 1, which shows the schematic of a plant which produces the yarn in accordance with the present invention.
Step (a) involves loading suitable silos (1), from which the polyamide is progressively fed into the production cycle.
Step (a) involves the addition of the antibacterial to the polyamide;
the antibacterial is preferably added in the form of a polyamide based master batch; the addition is carried out via suitable dispensers (2), e.g. gravimetric dispensers; the dispensing system can include an on-line control system which guarantees the exact dosage and shows up any anomalies, signalled by alarms; in this step other substances can be added, for example dyes, via systems (2') analogous to those described for the antibacterial.
In step (b) the polyamide to which the antibacterial is added passes into a suitable extruder (3); preferably a monoscrew extruder is used complete with static mixer; extrusion occurs generally at a temperature between 240 and 320°C, typically at 280°C; the extrusion step can also be supervised on-line, with suitable alarm thresholds; the extruded product passes preferably through an in-line filter (4) which guarantees, in addition to filtration, an improved mixing of the materials and a reduction of gels which possibly form.
In step (c) the material is conveyed to the spinning heads, where it is dispensed by the spinning pumps (5); the molten material, divided into filaments in the form predetermined by the design of the die passes through suitable cooling conduits (6) where it is cooled by an air flow having a well defined flow rate, temperature and moisture content and maintained under on-line supervision with alarm threshold.
In step (d) one or more of the following fibre conditioning processes take place, particularly useful for producing carpet yarns:
d1): the now cooled yarn receives the lubrication oil and is subjected to the drawing step by means of hot rollers (8) (heated to a temperature < 180°C) set to different speeds; the drawing step confers the necessary mechanical characteristics to the yarn;
(d2) the yarn is conveyed to the hot air texturizers (9) (heated to a temperature > 200°C) where yarn voluminizing (texturizing) takes place;
(d3) the yarn is subjected to interlacing, which confers to the yarn workability characteristics on the looms;
(d4) the yarn is subjected to enhancing processes such as twisting and/or heat-setting: these treatments confer to the yarn the characteristics of, for example, maintaining twist even after intense use of the carpet, as well as aesthetic characteristics such as fibrillated and uptwisted effects. Heat-setting is generally undertaken in hot air (Suessen process) under severe temperature conditions (190°C), or in the presence of O₂ and steam (Superba process).
At the end, the yarn is used directly on the looms, or is gathered on bobbins by a winding machine (10), to be woven later.
The fibres obtained by the aforesaid process are a further aspect of the invention. The antibacterial is contained in the fibres in quantities preferably between 2500 and 5000 ppm. The fibres thus obtained are endowed with antibacterial action, as confirmed by suitable bacterial growth tests, shown in the experimental part. From the mechanical and aesthetic viewpoints, adding the antibacterial has not resulted in any variation of the mechanical and aesthetic characteristics of the fibres produced in this way. Moreover, no significant antibacterial losses were observed, and essentially all the antibacterial used is incorporated in the yarn in a uniform and stable manner. In further usage tests no transfer of antibacterial into the environment was observed.
The carpet production step is carried out in accordance with traditional techniques used in the field. The invention, here described in relation to carpet production, can be applied also to the production of other covering and flooring textiles, for example carpets, runners, mats, bedside rugs, doormats and the like. These products, obtained by the aforedescribed process, comprise a further aspect of the present invention. The invention also includes the use of the yarn, obtained by the aforedescribed process, for preparing the aforesaid flooring textiles.
The following non-limiting examples further illustrate the invention.

Experimental part

Experimental test of dTex 1250 F 68 yarn, with the addition of 1.2% master Alpha san RC 5000 (Milliken).
The test was conducted in a Rieter JO10 plant, capacity 250 g/min (5700 kg/gg), polymer Pa 6 Vr 2.7, standard process parameters with a polymer temperature of 260°C. Drawing speed 2200 m/min, draw ratio 1:3. From the same single yarn produced, yarn samples of 1250 F 68 x 2 Twist 170 tpm heat set Suessen and 1250 F 68 x 2 twist 170 tpm heat set Superba were made up.
Effectiveness against bacteria was determined by the drop method (modified AATCC method 100) at the US Milliken laboratories. The individual samples were tested against Klebsiella pneumoniae ATCC#4352 and Staphylococcus ATCC#6538.
The results of the test are illustrated in figure 2: all the samples treated with Alpha San exhibit a moderate to very high effectiveness against microbes, while the untreated heat set Suessen yarn shows an actual greater bacterial growth than the reference PES support (the moderate antibacterial activity of one of the untreated samples was only temporary, due to the lubrication oil still being present).

Claims

Process for preparing an antibacterial yarn suitable for preparing flooring textiles, characterised by the following steps:

a) mixing together polyamide and an antibacterial agent containing silver

b) extruding the material thus formed

c) spinning the extruded material, to obtain fibres containing the incorporated antibacterial

d) executing one or more of the following fibre conditioning treatments: drawing, texturizing, interlacing, twisting, heat setting.
Process as claimed in claim 1, wherein the antibacterial is added to the polyamide in the form of a polyamide based master batch.
Process as claimed in claims 1-2, wherein the antibacterial is in the form of particles of dimensions between 0.1 and 1 micron.
Process as claimed in claims 1-3, wherein the antibacterial is a molecule containing silver atoms or ions, or is a carrier containing silver, its salts or oxides, in dispersed form.
Process as claimed in claim 4, wherein the carrier is an ion exchange resin.
Process as claimed in claims 1-5, wherein the antibacterial is used in quantities such as to obtain, in the finished yarn, concentrations between 2500 and 5000 ppm by weight.
Process as claimed in claims 1-6, wherein the extrusion takes place within a temperature range of between 240 and 320°C.
Process as claimed in claims 1-7, wherein the drawing step takes place by passing the fibre over rollers heated to a temperature less than 180°C.
Process as claimed in claims 1-8, wherein texturizing takes place at a temperature greater than 200°C.
Process as claimed in claims 1-9, wherein heat setting is effected by treating with hot air or in the presence of oxygen and steam.
Process as claimed in claims 1-10, for preparing flooring textiles chosen from carpets, fitted carpets, runners, mats, bedside rugs, doormats and similar products.
Antibacterial yarn suitable for producing flooring textiles, obtained by the process described in claims 1-11.
Yarn as claimed in claim 12, in the form of BCF yarn.
Yarn as claimed in claims 12-13, containing the antibacterial in a concentration between 2500 and 5000 ppm by weight.
Use of the antibacterial yarn obtained by the process described in claims 1-11 for manufacturing flooring textiles.
Use as claimed in claim 15, wherein said flooring textile is chosen from carpets, fitted carpets, runners, mats, bedside rugs, doormats and equivalent products.
Flooring textile based on fibres obtained by means of the process described in claims 1-11.
Textile as claimed in claim 17, chosen from carpets, fitted carpets, runners, mats, bedside rugs, doormats and equivalent products.