Field of the invention

The invention relates to the colouring (dyeing,printing) of polypropylene supports, such as fibres, films, moulded products, etc. and especially to the dyeing and/or printing of carpets (such as tufted carpets, woven carpets, non woven carpets, etc.), fabrics, etc. made at least partly of polypropylene fibres or threads and/or the printing of films .

The prior art

Polypropylene is well-known to be a material difficult to be printed and/or dyed.

It is well known that the dying of polypropylene fibres by using common dying technique is difficult and that no correct dyed polypropylene fibres can be achieved.

Therefore the most common method for preparing coloured polypropylene fibres is to include solid pigment in the polypropylene composition before its spinning.

In order to solve said problem, it is known to add some amide derivatives (polyesteramides, polyetheramides, copolyamide) to the polypropylene composition. Such additives are disclosed in US 6,679,754.

Polypropylene/polystyrene fibres are disclosed in US 6,248,835. However, said patent is silent about the dyeability of the fibres, and most especially to the dying of the fibres.

It has now been discovered that polypropylene supports could easily be printed and dyed by using known dying and printing methods by adding some polystyrene to the polypropylene. It has among others been discovered that polypropylene fibres

had an excellent dyeability when some polystyrene was added and when the dying was operated in presence of at least some acid(s) and at least carried out partly at temperature higher than 130°C and under pressure.

It has further been discovered that the printed or dyed PP/PS support was more soft than a common PP support, whereby increasing the touch character of the support, fibres or threads.

The invention will now further be disclosed.

Description of the invention

The invention relates to a colouring process of Polypropylene/polystyrene support, especially fibres, films, etc. (such as a dying process or a printing process), in which the support (fibres, film, etc.) is coloured (dyed or printed with one or more dyes) by means of an aqueous composition comprising from 0.1 to 4% by weight disperse dye, organic acid with 1 to 6 carbon atoms, and at least a surfactant, whereby said colouring is at least operated partly at a temperature higher than 90 ⁰ C. When dyeing, the colouring step is advantageously carried out at least partly at a temperature higher than 130°C and under pressure higher than 10 ⁵ Pa.

It has been observed that best colouring (dying, printing) of the support was achieved when the polypropylene/polystyrene support (fibres, film, etc.) has a polystyrene/polypropylene weight ratio comprised between 1 :20 and 1 :4, preferably between 1:10 and 1:5. When using polypropylene support (fibres, films, etc.) with a weight ratio polystyrene/polypropylene comprised between 13:87 and 17:83, the colouring (dying, printing) ability or suitability of the support (such as fibres, films, etc.) was quite constant, meaning an easy control of the dying process.

Advantageously, the organic acid with 1 to 6 carbon atoms is present in the composition, so that the pH is comprised between 3 and 5, preferably about 4.

According to an embodiment, the pH of the colouring (dying, printing) composition is maintained at a substantially constant pH by addition of acid during the dying process.

Preferably, at least citric acid is used as organic acid.

Most preferably, the organic acid content of the composition is comprised between 1 and lOg/1, preferably between 1 and 5g/l.

According to detail of preferred embodiments, the colouring (dying, printing) is at least operated at a temperature higher than 130 ⁰ C during at least 5 minutes, advantageously at least 10 minutes, preferably at least 15 minutes. For example the temperature is comprised between 130 ⁰ C and 170 ⁰ C, such as from 140 ⁰ C to 150 ⁰ C, during at least 5minutes, advantageously at least 10 minutesn preferably 15 minutes.

The support (such as fibres, films, etc.) can comprise one or more other additives. However, advantageously, the support (fibres, films, etc.) comprises more than 90% by weight polypropylene and polystyrene, preferably more than 95% by weight, more preferably more than 99% by weight.

According to specific embodiment, the dying is operated at least partly at a temperature comprised between 140 ⁰ C and 150 ⁰ C and/or (preferably and) at least partly at a pressure comprised between 1.5 10 ⁵ Pa and 10 10 ⁵ Pa.

After being coloured (dyed or printed), the support (fibres, films, etc.) are advantageously washed and dried. When printed, the support (fibres, threads, films, etc.) is advantageously submitted to a fixing step after being coloured or printed, said fixing step being carried out advantageously during a time comprised between 5 and 40minutes, preferably between 10 and 25 minutes. Said fixing step is advantageously carried out at a temperature higher than 80 ⁰ C, preferably greater

than 110°C, such as a temperature comprised between 8O ⁰ C and 130°C, preferably comprised between 110°C and 13O ⁰ C.

Preferably, the fibres form threads, whereby the threads are coloured (dyed or printed) .

The invention relates also to :

- a coloured (dyed or printed) polypropylene/polystyrene support, especially fibres or threads or films prepared at least partly by a process of the invention as disclosed here above in the present specification,

- a product comprising at least coloured (dyed or printed) polypropylene/polystyrene support (such as fibres, threads, films, etc. and combinations thereof) of the invention, said product being advantageously selected from the group consisting of woven fabrics, non woven fabrics, carpets (such as tufted carpets, woven carpets, non woven carpets, etc. and combinations thereof), garments, filter media, furniture upholstery, synthetic paper, films, moulded articles, packaging material and combinations thereof, and

- a polypropylene/polystyrene support comprising a matrix made essentially of Polypropylene and Polystyrene, whereby the weight ratio polystyrene/polypropylene is comprised between 1:10 and 1:5, preferably between 12:88 and 17:83, especially about 15:85, whereby said support comprises advantageously from 0.05% and 1% by weight of at least an organic acid with 1 to 6 carbon atoms, preferably citric acid, said matrix comprising advantageously at least 85% by weight, preferably at least 90% by weight (such as 95% by weight or even more) of polypropylene and polystyrene, .

The polypropylene used in the fibres, threads, films or supports of the invention or used in the coloured process of the invention can be a homo polypropylene or a copolymers, a copolymer of polypropylene with polyethylene, such as with HDPE (high density polyethylene, LLDPE linear low density polyethylene, random and

impact copolymers. The polypropylene can be prepared by radical polymerization, catalytic polymerization. Possibly the polypropylene can be mixed with some other polymers than polystyrene, such as polyethylene (High density PE, Low density PE, Medium Density PE). The content of other polymers than polystyrene in the polypropylene can be up to 15% by weight. However the content of other polymers is preferably lower than the polystyrene content thereof.

The polypropylene/polystyrene fibres, threads, supports of the invention or used in a method of the invention can comprises one or more additives, such as UV absorbers, stabilizers, antioxidants, processing aids, metal deactivators, phosphites, phosphorates, hydroxylamines, nitrones, amine oxides, benzofuranones, indolinones, thiosynergists, peroxide scavengers, co stabilizers, nucleating agents, fillers, reinforcing agents, dispersing agents, lubricants, cross-linking agents, flame proofing agents, antistatic agents, catalysts, rheology additives, flow-control agents, gums, dyes, powder dyes, etc. Examples of such additives are given in US 6,679,754.

The invention relates also to a polypropylene/polystyrene particles intended to be used for the preparation of a support suitable to be processed in a process according to the invention, said particles being characterized in that each particles comprises polystyrene and polypropylene, preferably in the form of a blend of polystyrene and polypropylene.

Advantageously, the particles has an average particle size comprised between lOμm and 10mm, advantageously between lOOμm and 5mm. The particles have advantageously the form of flakes, beads or granules.

Preferably, the particles are characterized by a polystyrene/polypropylene weight ratio comprised between 1 :20 and 1 :4, preferably between 1 :10 and 1 :5.

For example, the weight ratio polystyrene/polypropylene is comprised between 1:10 and 1 :5, preferably between 12:88 and 17:83, especially about 15:85.

Preferably, the particles have a substantially homogeneous composition.

The particles comprises advantageously one or more additives and/or fillers, such as UV absorbers, stabilizers, antioxidants, processing aids, metal deactivators, phosphites, phosphonites, hydroxylamines, nitrones, amine oxides, benzofuranones, indolinones, thiosynergists, peroxide scavengers, co stabilizers, nucleating agents, fillers, reinforcing agents, dispersing agents, lubricants, cross- linking agents, flame proofing agents, antistatic agents, catalysts, rheology additives, flow-control agents, gums, dyes, powder dyes, etc. Examples of such additives are given in US 6,679,754.

Examples

Preparation of Polypropylene (PP) / Polystyrene (PS) fibres

Commercially polypropylene for fiber application has been mixed with polystyrene and with an UV stabiliser. The mixture is fed into an extrusion spinning facility and processed into continuous threads.

The polypropylene used has a Melt Flow rate (MFR ASTM - 1238 L) lower than 80g/10minutes, preferably lower than 30g/10minutes. While the density (ASTM - D1505) of the PP can vary from 0.90 and 0.91 (g/cm ³ ). The melting point of said polypropylene was about 165°C (DSC). Other properties of the polypropylene are elongation of about 30 to 40%, tenacity of 3 to 5g/denier, linear skein shrinkage (ASTM D3218) of about 3 to 4.5%, a softening point from about 150°C and 220°C (ASTM D- 1525). The Polypropylene is advantageously amorphous. The used polypropylene has advantageously a Tg of about 0°C.

The following PP have been used in the preparation of PP/PS fibres.

The Polystyrene used in the preparation of the PP/PS fibres has the following properties : Melt flow rate (ASTM D- 1238 from 1 to 30g/min, preferably substantially equal to the MFR of the PP to which the polystyrene is added); a Vicat softening point comprised between 160 ⁰ C and 220°C (ASTM D- 1525), a tensile strength comprised between 40 and 70 Mpa (ASTM D-638), crystal atactic or syndiotactic (advantageously syndiotactic), density from 1.01 to 1.06 (ASTM D 792). The used polystyrene has advantageously a Tg of about 100°C.

The following mixtures have been used for preparing the fibres and the threads to be coloured. In said mixtures, the UV stabilizer used was the product Tanvin ®.

The Tg of the so prepared blend was lower than 100°C, but greater than 0°C. It was also observed that the addition of polystyrene to the polypropylene decreased the crystallinity of the polypropylene and increased the hygrogroscopicity or the property to absorb water moisture with respect to polypropylene alone.

The fibres and threads are produced according to known techniques, such as extrusion spinning fixture. The fibres and threads can thereafter be coloured or printed, possibly after a post process step, such as a step for producing a fabric, woven fabric, a non woven fabric, carpet (tufted carpet, woven carpet, non woven carpet, combinations thereof), loop and cut pile carpets, floor covering, yarns, textile, artificial leather, etc.

Colouring step

Threads prepared from the mixtures 1 to 15 have been coloured according to the following processing.

Stage 1

The threads are winded on a metal perforated support, such as cones. The threads have been prewashed at 70°C in an aqueous bath with a soap, back washed and rinsed.

A dyeing bath has been prepared as follows : water has been mixed with a levelling agent (anionic/ non ionic), a dispersant, a lubricant and citric acid. A dispersion dye suitable for polyester is added and mixed to the bath. Said mixing is advantageously made at a temperature of about 5O ⁰ C.

The dyeing bath had a pH of about 4, a disperse dye content comprised between 2 and 4%, a levelling agent or leveller content of about lg/1, a dispersant agent of about lg/1, a lubricant content of about lg/1. The citric acid content is of at least 0.5 g/1 and is adjusted so as to achieve the desired pH, such as about 3.5 or about 4. Levelling agent or leveller, dispersant are well known for disperse dyes. The agitation of the bath has been maintained during at least 15 minutes, preferably from 20 to 40 minutes.

Examples of disperse dyes used for colouring the fibres or threads are : Introsol disperse dyes, such as Introsol Red 73 GL 200%, Introsol Yellow 4G, Introsol Blue 73 BG 200%, Trasil Navy Blue GRL- C 200%, Tracil dye from Ciba.

The threads to be coloured have been dipped in the colouring bath prepared in stage 2. After dipping the thread, the temperature of the colouring bath is maintained during 15 minutes at a temperature of 50 ⁰ C. After said first colouring

step, the temperature of the bath is increased to about 13O ⁰ C. The bath is closed, so that said colouring step is carried out under pressure (pressure higher than about 2 10 ⁵ Pa) during 20 to 40 minutes, especially about 30minutes. It has been observed that the softness of the coloured fibres or threads was improved by such a heat treatment. Thereafter the colouring bath is cooled down to 75 °C and maintained at said temperature for 15minutes.

Stage 4

The threads present in the bath are submitted to a reduction cleaning for 10 minutes, said cleaning being carried out by adding 2.75g sodium hydroxide and 2.75g sodium hydrosulfϊte per litre of bath. Said reduction cleaning is carried out at a temperature of 75°C.

Stage 5

The bath is cooled to 50°C and is neutralized with addition of formic acid at a rate of 0.25g/l.

Stage 6

The supports with the dyed threads are removed from the bath, rinsed and dried. The dried threads are rewound on carton cones.

When carrying the colouring tests, it appears that the colouring was excellent when the polystyrene content in the mixture was higher than 10%, especially between 13% and 17%. It appears also that with such a Polystyrene content, possible variations of 10% of a parameter (such as duration, pH, concentration of additives) in the colouring methods were not affecting the quality of the end coloured product.

It was also observed that the dyed fibres and threads had an improved soft or touch with respect to the non dyed fibres and threads, as well as with respect to the PP fibres or threads. The softness of the dyed fibres and threads was similar to that of acrylic fibres.

Printing

The printing of a support made from fibres or threads or tuft or felt of PP/PS, such as a carpet (tufted carpet, woven carpet, non woven carpet), was made with a Chromo Jet (Zimmer) machine. According to a further embodiment, the fibres or threads was containing a dye, such as a powder dye, so that the fibres or threads have a basic colour. The printing of such fibres or threads is then equivalent to an overprinting.

The printing composition was prepared as follows :

A disperse dye was mixed with water, with an anionic thickener (10 to 30g/l), a nonionic levelling agent (1 to 3 g/1) and citric acid (2 to 3 g/1, so as to adjust the pH up to about 4). The content of disperse dye in the composition is from 2 to 4g/l.

Examples of possible disperse dyes suitable for printing are Tracil Yellow CR, Tracil Red CB, Tracil Blue C3B (Ciba Geigy)

The composition applied on the support was heated at a temperature of 95 to 98°C The printing was fixed by keeping the temperature at 95-98 ⁰ C for about 15minutes.

In another printing process, the composition applied on the support was heated at a temperature of about 100°C, while the printing was fixed by keeping the temperature at about 120°C for about 15minutes. Such a heat treatment at about 120°C (fixation step of the printing) resulted in a better softness texture and a very good fixation of the printing.

It has been observed that a carpet ( tufted carpet, woven carpet, non woven carpet) made from fibres or threads dyed according to the first example of dying method was able to be overprinted according to the printing process.

Tested Yarns

Various yarns have been tested, before and after printing according to the method of the invention.

PP and PS are the weight content respectively in Polypropylene and Polystyrene * : measured according to the Norm ASTM D 1907-01, average value expressed in Denier. C.V.%* : coefficient of variation of the average yarn count, expressed in % ** : measured according to the AST D 2256-02 Norm CV. % : coefficient of variation expressed in % *** : measured according to Norm B. S. 3/49

As it can be seen from the previous table, the yarn containing 13% PS and having an average yarn count of about 1052 denier has properties very similar to the Nylon reference. When using 15 to 20% PS in the blend, there is substantially no difference with respect to the properties (yarn count, breaking strength and coefficient of friction).

PP and PS are the weight content respectively in Polypropylene and Polystyrene

* : measured according to the Norm ASTM D 1907-01, average value expressed in

Denier.

C.V.%* : coefficient of variation of the average yarn count, expressed in %

** : measured according to the AST D 2256-02 Norm

CV. % : coefficient of variation expressed in %

*** : measured according to Norm B. S. 3/49

This table shows that yams with a 2600 denier containing already about 10% PS have properties similar to the PP yarns with a weight of 2600 denier.

The yarns with a weight of 2600 denier were used for producing a carpet. The so prepared carpets were pressed for 24 hours and the height of the carpet pile was measured in function of the time after removal of the pressure. It appears from said test that the PS-PP yarns of the invention were more suitable for recovering their height before being pressed. It appears that with the PS-PP yarns of the invention 60% of the height could be recovered in two minutes, while with the PP yarns, more than 2 hours were necessary for recovering 60% of the height. 24 hours after the removal of the pressure, 80% of the height was recovered with the PP-PS yarns of the invention, while more than 55hours were necessary for the PP yarns.

The carpet prepared by the PP-PS yarns of the invention had thus better performance against static loading.

Examples of supports

Various supports have been prepared, namely :

Carpets, tufted carpets, woven carpets, non woven carpets : soft, stain resistance, easy to wash or clean, dust resistance (dust can easily be removed by suction).

Garments : soft, stain resistance, easy to wash , possibility to replaced sewing points or lines by melting, gluing, etc.

Films or layers: film can be made in PP/PS in various quality and thickness by the known techniques, such as extrusion/blowing, etc. The films can be used for various purposes, such as bags, packaging film, sealing film, food sealing films, unidirectional film, etc. The film is easily printable and has good barrier property (oxygen barrier property), with low release of inner compounds. The film can be unidirectional, bi directional, embossed, can be laminated with one or more further

layers, such as polyethylene layer, etc. the film or layer can be reinforced with other fibres, such as glass fibres, carbon fibres, etc. The films or layers can be attached to a support, such as a flexible support, a latex layer, a foam layer, etc. but can also be overcoated with one or more protection layers.

Bank notes

Foam support : with open or closed cells

Moulded supports, such as for the automobile, etc.

Bags

Bottles, food containers,

Web, fibres web

Diapers

Apparel: Activewear and sportswear; socks; thermal underwear; lining fabrics

Automotive: Interior fabrics used in or on kick panel, package shelf, seat construction, truck liners, load decks, etc.

Home Furnishings: Indoor and outdoor carpets; carpet backing; upholstery and wall coverings; furniture and bedding construction fabrics

Industrial: Carpets; disposable, durable nonwoven fabrics; ropes; filter fabrics; bagging; geotextiles

It has been observed that when submitting a coloured fabric of the invention, especially a woven fabric to a calendaring step at a temperature comprised between

110 and 13O ⁰ C, it was possible to further increase the softness texture of the fabrics.

Examples of particles PP/PS

Commercially polypropylene has been mixed homogeneously with polystyrene and with an UV stabiliser. The mixture is fed into an extrusion facility and processed into continuous threads, which are cut in granules or flakes or which are shaped in beads. The weight average particle size of the particles was controlled respectively to lmm, 2mm, 3mm and 5mm. The particle size distribution can also be multi modal, such as bi-modal, i.e. having the form of a mixture of two different type of particles, such as a first fraction of particles having an average particle size lower than 2mm and a second fraction of particles having an average particle size greater than 3mm.

The polypropylene used has a Melt Flow rate (MFR ASTM - 1238 L) lower than 80g/10minutes, preferably lower than 30g/10minutes. While the density (ASTM - Dl 505) of the PP can vary from 0.90 and 0.91 (g/cm ³ ). The melting point of said polypropylene was about 165°C (DSC). Other properties of the polypropylene are elongation of about 30 to 40%, tenacity of 3 to 5g/denier, linear skein shrinkage (ASTM D3218) of about 3 to 4.5%, a softening point from about 15O ⁰ C and 220 ⁰ C (ASTM D-1525). The Polypropylene is advantageously amorphous. The used polypropylene has advantageously a Tg of about 0 ⁰ C.

The following PP have been used in the preparation of PP/PS particles.

The following mixtures have been used for preparing the particles suitable for preparing the threads to be coloured. In said mixtures, the UV stabilizer used was the product Tanvin ®.