SEMI-SYNTHETIC MATERIAL

FIELD OF THE INVENTION

The present invention relates to a modified ultra-fine natural fibre powder and to a process for the preparation of the modified ultra-fine natural fibre powder. The present invention also relates to a semi-synthetic material, in particular a semi-synthetic fibre or filament. The present invention further relates to a method of preparing a semi-synthetic material.

BACKGROUND

The conversion of natural fibres, such as wool, into textile articles is a very lengthy and costly one. In contrast, the production of manufactured fibres is a rapid process. Wool and other animal fibres have unique properties such as good dye uptake and moisture absorption, which make the fibre comfortable to wear. They also have some disadvantages in areas such as low strength and stability. Manufactured fibres are usually strong and stable. Blending of animal fibres with manufactured fibres can therefore potentially take advantage of the good attributes of both fibre types.

Traditionally, wool fibres are blended with manufactured fibres in a conventional wool processing facility. This has a number of drawbacks, including the filaments must be converted into staple fibres with a length similar to wool; the processing chain is very long and costly; and the textiles made from the blend may suffer from problems such as pilling.

Unlike manufactured fibres, wool, for example, has a complex crystal structure in which the protein molecules are the building blocks in a structure derived from the growth of specialised follicle cells in the skin of sheep. Each fibre consists of a core of spindle-shaped cortical cells enclosed by flattened cuticle cells. The cortical cells are the major structural component and make up more than 95% of the fibre mass. Each cortical cell is about 100 microns long and 5- 7 microns wide. Cortical cells are composed of about 20 macrofibhllar bundles of microfibrils aligned approximately parallel with the axis of the cortical cells and embedded in a matrix of amorphous protein. Each microfibril is made up of

a bundle of about 7 rod-like intermediate filaments which are about 2 nm in diameter. In turn, each intermediate filament is composed of four left-handed coils each containing two right-handed polypeptide α-helices. Thus, the various fibrillar components vary in size from the nanometre to micrometre scale in diameter.

Heretofore, it has proved impossible to extrude wool blends with polyolefins such as polypropylene (PP), polyamides such as Nylon 6 (PA6) and polyesters such as PET by melt forming processes such as melt spinning because of the high temperature involved in the extrusion process, which degrades the natural polymer material (eg. wool).

Moreover, synthetic fibres, especially polypropylene (PP), are difficult to dye. It is also known that the regain (% by weight of water present) of pure PP fibres is close to zero percent. Further, PET fibres need high temperatures for dyeing, thus requiring specialist equipment and high energy input.

It is accordingly an object of the present invention to overcome, or at least alleviate, one or more of the difficulties of deficiencies of the prior art.

The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Throughout the description and claims of the specification, the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps.

SUMMARY

Accordingly, in one aspect of the present invention, there is provided a modified ultra-fine natural fibre powder for use in a melt forming process for the

preparation of a semi-synthetic material including said ultra-fine natural fibre powder and a synthetic polymer component, the powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particles during said melt forming process.

In another aspect of the present invention there is provided a process for preparing a modified ultra-fine natural fibre powder for use in a melt forming process for the preparation of a semi-synthetic material including said ultra-fine natural fibre powder and a synthetic polymer component, which process includes the steps of

• providing:

(i) a source of ultra-fine natural fibre powder; and

(ii) a stabilizing agent to improve the heat stability of the natural fibre powder particles during said melt forming process, and

• mixing the components for a time sufficient to couple the stabilizing agent to the natural fibre powder.

In another aspect of the present invention there is provided a semi-synthetic material formed by a melt forming process, the material including

• a synthetic polymer component; and

• a modified ultra-fine natural fibre powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particle during the melt forming process.

Preferably the semi-synthetic material is a semi-synthetic fibre or filament.

In another aspect of the present invention there is provided a method for the preparation of a semi-synthetic material, which method includes • providing:

(i) a synthetic polymer component; and

(ii) a modified ultra-fine natural fibre powder including particles of a natural fibre modified with a stabilizing agent to improve the heat stability of the natural fibre powder particles;

• blending the components; and

• subjecting the blended components to a material formation step using a melt forming process.

In another aspect of the present invention there is provided a method for the preparation of a semi-synthetic fibre or filament, which method includes

• providing:

(i) a modified ultra-fine natural fibre powder including particles of natural fibre modified to improve the heat stability of the natural fibre powder particles; and

(ii) a synthetic polymer component;

• blending the components; and

• subjecting the blend to a melt spinning step at elevated temperatures.

In preferred embodiments, the particles of natural fibre are modified with a stabilizing agent, more preferably a heat stability coating. A polymeric heat stability coating, for example, a polymeric sterically hindered phenol coating, is preferred.

BRIEF DESCRIPTION OF THE FIGURES

Figures 1A, B and C illustrate wool powders dyed with (A) Lanasol Blue CE,

(B) Lanaset Navy R and (C) Solar Blue 3GLN, respectively, produced in accordance with Example 1.

Figure 2 illustrates knitted polymer yarns dyed at 100 ⁰ C with Lanaset Navy R.

Left to right: pure polypropylene, polypropylene containing 2% W powder, polypropylene containing 2% G powder, respectively, produced in accordance with Example 2.

DETAILED DESCRIPTION

It has been found that semi-synthetic materials, e.g. fibres or filaments, according to the present invention may exhibit one or more of the favourable properties of the natural fibre.

For example, the semi-synthetic materials obtained may exhibit good dyeability and antistatic properties. Further, the excessive lustre of conventional man- made filaments may be reduced. One or more of advantages of manufactured fibres, for example strength, dimensional stability, as well as good wash and good wear properties, may be preserved. Thus, the properties of the semisynthetic materials according to the present invention may combine one or more desirable characteristics from both natural and manufactured fibres.

Further, without wishing to be limited by theory, it is postulated that when implanting natural fibrillar powders, which are nanometre or micrometer in size into synthetic polymers, an extensive domain crystal structure may be established. This type of structure may result in improvement in properties of the material, including improvement in the absorption and dyeability of fibres prepared from the material. The dyeing may be conducted even at normal pressure but with a high dye uptake. The antistatic property of the material may also be improved.

Moreover, the excessive lustre appearing on conventional synthetic filaments may be reduced when the proportion of the natural fibre powders is about 0.5% by weight.

In one aspect, the present invention provides a modified ultra-fine natural fibre powder for use in a melt forming process for the preparation of a semi- synthetic material including said ultra-fine natural fibre powder and a synthetic polymer component, the powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particles during said melt forming process.

As used herein, the term "natural fibre" refers to proteinaceous fibre material of animal origin.

The particles of natural fibre may be modified with a stabilizing agent to improve the heat stability of the natural fibre. One or more stabilizing agents

may be included. In one embodiment, the particles of natural fibre may bear a heat stability coating. The heat stability coating protects the natural fibre particles from heat degradation at the melting temperature of the synthetic polymer component. Without wishing to be limited by theory, it is believed that one advantage of the invention is that modification of the natural fibre particles preserves the properties of the natural fibre by preventing or reducing denaturation of the fibre's protein structure when the natural fibre is exposed to heat.

Preferably, the modified ultra-fine natural fibre powder may be resistant to temperature degradation up to a temperature of approximately 230 ⁰ C, more preferably up to approximately 195°C.

When used, the heat stability coating may be of any suitable type. For example a polymeric coating such as a polymeric sterically hindered phenol (PSHP) coating may be used as the stabilizing agent. An example of a PSHP is

Lowinox® CPL. The polymeric coating may include one or more suitable polymers. The person skilled in the art would understand however that the nature of the stabilizing agent may vary, depending on the synthetic polymer component and the melt forming process conditions required. In addition, a conditioning agent, such as a polyethylene glycol (PEG), may be used to improve the rheological behaviour of the polymer melt for extrusion.

In another aspect, the present invention provides a semi-synthetic material formed by a melt forming process, the material including

• a synthetic polymer component; and

• a modified ultra-fine natural fibre powder including particles of a natural fibre modified to improve the heat stability of the natural fibre powder particle during the melt forming process.

The synthetic polymer component used in the invention may be of any suitable type. Preferably, the synthetic polymer component includes at least one thermoplastic polymer. For example, a polyolefin such as polyethylene (PE) or polypropylene (PP) may be used. An acrylic polymer such as polyacrylonithle

(PAN) may be used. A polyamide, for example Nylon 6 or Nylon 66, or a polyester such as polyethyleneterephthalate (PET) may be used. The synthetic polymer component may be present in amounts of from approximately 90 to 99.5% by weight, preferably approximately 95 to 99% by weight, based on the total weight of the semi-synthetic material. A mixture of polymers may be included in the synthetic polymer component.

The semi-synthetic material of the invention also includes a modified ultra-fine natural fibre powder as described herein.

The particles of the ultra-fine natural fibre powder may be produced from any suitable animal source. An animal fibre, or mixtures thereof, may be used. An animal fibre such as wool or hair obtained from animals such as sheep, goats, llamas, alpacas, rabbits etc, is preferred. A sheep wool, mohair or alpaca, or mixtures thereof, may be used.

The modified ultra-fine natural fibre powder may include particles of natural fibre of any suitable size and shape. In a preferred embodiment, the ultra-fine natural fibre powder may include particles having mean diameters in the range of from approximately 5 nm to 10 μm, preferably approximately 1 to 7 μm, more preferably approximately 2.5 to 5 μm, and even more preferably approximately 2 to 5 μm. The powder particles preferably have a length of no greater than approximately 250 μm, more preferably not greater than 200 μm, most preferably not greater than approximately 100 μm.

The modified ultra-fine natural fibre powder component may be present in amounts of from approximately 20 to 0.25% by weight, preferably approximately 10 to 0.5% by weight, more preferably approximately 5 to 0.5% by weight, based on the total weight of the semi-synthetic material.

The particles of the ultra-fine natural fibre powder may be formed utilising any suitable technique. The ultra-fine natural fibre powder may be formed utilising chemical, enzymatic or mechanical processes or combinations thereof. The technique disclosed in Xu, Weilin et al., Powder Technology (2004) 140 (1 -2),

pp136-140, provides a suitable technique for the preparation of the ultra-fine natural fibre material and is incorporated herein by reference.

As discussed above, an advantage of the semi-synthetic material according to this aspect of the present invention is its ability to take up dyes. Accordingly, in a preferred aspect, the semi-synthetic material according to the present invention may further include a dye component. The semi-synthetic material may be dyed with any conventional dyes by any method suitable for dyeing natural fibres which would be known to a person skilled in the art. For example, conventional wool dyes may be used. Dyeing may, for example, be conducted at temperatures in the range of approximately 100 ⁰ C to 130 ⁰ C.

For example, dyes such as Lanasol, Lanset or Solar dyes, e.g. Lanasol Blue CE, Lanset Navy R and Solar Blue 3GLN may be used.

In another aspect of the invention, the modified ultra-fine natural fibre powder may be dyed before incorporation in the semi-synthetic material with any of the appropriate dyes which would be known to a person skilled in the art. For example, dyes such as Lanasol, Lanset or Solar dyes, e.g. Lanasol Blue CE, Lanset Navy R and Solar Blue 3GLN may be used. Dyeing may conducted under any appropriate conditions and may, for example, be conducted at room temperature. The particles of the natural fibre powder may be dyed before or after undergoing modification to improve heat stability.

Due to the large surface area of the ultra-fine natural fibre powder, uptake of the dye is very efficient. Anionic dyes are particularly advantageous as they are readily absorbed by ultra-fine natural fibre powder at low to neutral pHs. The efficient and low temperature uptake of dye by the ultra-fine natural fibre powder is economically advantageous.

In a further aspect of the present invention there is provided a method for the preparation of a semi-synthetic material, which method includes • providing:

(i) a synthetic polymer component; and

(ii) a modified ultra-fine natural fibre powder including particles of a natural fibre modified with a stabilizing agent to improve the heat stability of the natural fibre powder particles; • blending the components; and • subjecting the blended components to a material formation step using a melt forming process.

The modified ultra-fine natural fibre powder may be blended with the synthetic polymer component using any conventional blending process. An example of a suitable blending process involves mixing the modified natural fibre powder and the synthetic polymer component together.

The material formation step used to form the semi-synthetic material may be carried out using any melt forming process. A preferred melt forming process is an extrusion process. In one embodiment, the material formation step is a fibre or filament formation step. The fibre or filament formation step may be of any suitable type. A spinning step, e.g. a melt spinning step, may be used. In another embodiment, the semi-synthetic material may instead be formed as a sheet or film.

In a melt spinning process, the modified ultra-fine powder may be added to the molten synthetic polymer and thoroughly combined before the molten liquid is forced through a spinneret to form continuous filaments.

The modified ultra-fine natural fibre powders may be incorporated into the synthetic filaments with various distribution patterns depending on the type of extrusion head employed. For example, uniform distribution of the modified ultra-fine powders throughout a fibre or filament may be achieved by a normal extrusion head. Alternatively, the modified ultra-fine powders may be distributed solely in the surface of the fibre or filament by using sheath-core bi- component spinning or solely on one side of the fibre or filament using side-by- side bi-component spinning.

The material formation step is typically conducted at an elevated temperature that is sufficient to melt the synthetic polymer component. In a preferred embodiment, the material formation step may be conducted at temperatures of approximately 50 ⁰ C to 230 ⁰ C, depending on the synthetic polymer(s) selected. Conventionally, where elevated temperatures, for example, up to approximately 230°C are used, the natural fibre particles may exhibit some degradation over time due to denaturation of the fibre's protein structure.

However, modification of the ultra-fine natural fibre powder in accordance with the invention helps to stabilize the particles of the natural fibre powder upon exposure to heat.

Accordingly, in a further embodiment of the present invention there is provided a method for the preparation of a semi-synthetic fibre or filament, which method includes • providing:

(i) a modified ultra-fine natural fibre powder including particles of natural fibre modified to improve the heat stability of the natural fibre powder particles; and (ii) a synthetic polymer component; • blending the components; and

• subjecting the blend to a melt spinning step at elevated temperatures.

The synthetic polymer component may include any suitable polymer. Preferably, the synthetic polymer component includes at least one thermoplastic polymer. In preferred embodiments, the synthetic polymer component may include a polyolefin (e.g. PP), an acrylic polymer (e.g. PAN), a polyamide such as nylon (e.g. PA6) or a polyester (e.g. PET), or mixtures thereof.

The melt spinning step used for the formation of the semi-synthetic fibre or filament may be conducted in a conventional melt extrusion machine at any suitable temperature. Preferably, the melt spinning step is conducted at a temperature up to 230 ⁰ C but preferably below 200°C. The spinnability and

other processing properties of the blend may be similar to using the pure PP, low melting point PA6, or low melting point PET.

In a still further aspect of the present invention there is provided a process for preparing a modified ultra-fine natural fibre powder for use in a melt forming process for the preparation of a semi-synthetic material including said ultra-fine natural fibre powder and a synthetic polymer component, which process includes the steps of

• providing: (i) a source of ultra-fine natural fibre powder; and

(ii) a stabilizing agent to improve the heat stability of the natural fibre powder particles during said melt forming process, and

• mixing the components for a time sufficient to couple the stabilizing agent to the natural fibre powder.

The ultra-fine natural fibre powder may be formed from animal fibres as described herein. Preferred animal fibres may include wool, mohair, alpaca or mixtures thereof.

The stabilizing agent may be any suitable agent capable of improving the heat stability of the natural fibre powder. In one embodiment, the stabilizing agent may be a heat stability coating. The heat stability coating may be of any suitable type. For example a polymeric coating, such as a coating including a polymeric stehcally hindered phenol (PSHP), may be used as the stabilizing agent. An example of a PSHP is Lowinox® CPL. The polymeric coating may include one or more suitable polymers to modify the natural fibre powder for improved heat stability. In addition, one or more stabilizing agents may be used.

The ultra-fine natural fibre powder may be mixed with the stabilizing agent using any technique and for any time sufficient to couple the stabilizing agent to the particles of the natural fibre and thereby form a modified ultra-fine natural fibre powder. In one embodiment, the stabilizing agent may first be

dissolved or dispersed in a solvent and the resultant solution mixed with the ultra-fine natural fibre powder. Other techniques, for example, ultrasonication, may also be employed to assist the coupling of the stabilizing agent to the natural fibre powder.

The present invention will now be more fully described with reference to the accompanying examples. It should be understood, however, that the description following is illustrative only and should not be taken in anyway as a restriction on the generality of the invention described above.

EXAMPLES

EXAMPLE 1

Melt-spun wool blend filaments

This series of experiments was based on the inclusion of dyed ground wool powder in uncoloured polypropylene filaments. This is therefore a type of dope dyeing of polypropylene using coloured keratin particles.

A Preparation of polymer chips

Chips containing polypropylene were blended with ground wool powder (WP) prior to fibre extrusion. Three amounts of powder were separately dyed blue, red and black using Lanaset dyes. Undyed powder was used as a control. The dyeing was carried out by wetting out wool powder (WP) in an aqueous solution containing 10% by weight of dye on the weight of powder, at a liquor ratio of 70:1. The pH was adjusted using 3% acetic acid and the solution was agitated for one hour. The powder was then filtered off, dried and ground in a rotary knife mill.

1 WP samples were first mixed with a Stabilizing Agent (SA) (Lowinox® CPL) in the ratio WP:SA of 1 :0.22 to improve the heat stability of the WP. The SA was first dissolved in ethanol (AR), then the WP was added and the resultant slurry was mixed well and given an ultra-sonic treatment for from 20 to 105 minutes. The slurry was allowed to dry

naturally, and the cake obtained was ground and passed through a 100 mesh sieve.

The powder obtained in step 1 was mixed with polyethylene glycol (MW=20,000) powder which had been ground at low speed and passed through a 100 mesh sieve. The ratio of (WP+SA):PEG was 1 :0.45.

Polymer chips containing wool powder were then prepared by melt extrusion of PP together with the powder mixture obtained as described in step 2. The blend levels of WP in PP chips were as shown in Table 1 :

TABLE 1

The amounts of wool powder in the PP chips

B Extrusion of filaments

Batches of PP chips containing wool powder were extruded using a small pilot plant machine. The extrusion screw feed was set at 13.5 r/min and the temperature settings from the feed screw to the die were: for the Red and Blue wool powder (concentration 0.5%) 170 ⁰ C, 192°C, 192°C, 192°C and 192°C and for the Black and White (concentration 1.0%) 170 ⁰ C, 190 ⁰ C, 190°C, 190 ⁰ C and 190°C. Eighteen filaments were extruded at a speed of 500 m/min.

C Stretching of the filaments

After extrusion, the filaments were stretched at a ratio of 2.2:1 using the filament drawing machine, with the temperatures set at 60°C - 70 ⁰ C - 90°C (from the feeder roller to the front roller).

Single filaments produced in the experiments described above were measured for linear density, tenacity and elongation at break. Linear density was measured using the traditional cutting and weighing method. Tenacity and breaking elongation were measured with a SIFAN instrument using a gauge length of 25.4 mm and a motor speed of 500 mm/min. More than 40 tests were carried out on each sample. The results are shown in Table 2.

TABLE 2

Physical properties of the melt-spun blend filaments.

The results show that all the filaments containing wool powder were of similar linear density, tenacity and elongation at break within experimental error. The pure polypropylene extruded under the same conditions, had a slightly lower linear density, a slightly lower tenacity and the elongation at break was approximately 25% higher. The lower elongation at break for the filaments containing wool powder may have been as much a reflection of the other additives present as an effect due to the wool powder.

EXAMPLE 2

Dyeing of semi-synthetic filament Two types of filament were prepared: polypropylene and polypropylene containing 2% of two different preparations of undyed modified wool powder

made in accordance with the invention, designated W and G. Filaments were made by melt extrusion, as described in Example 1. The spinning speed was 250 m/min and the filaments had average diameters of around 20 microns. Samples of pure polypropylene filament and the polypropylene semi-synthetic filaments were knitted on a sample knitting machine. Knitted samples were dyed with the wool dye Lanaset Navy R, as follows.

Filament 19

Lanaset Navy R 1 %

Acetic acid 3%

Hydropol TN 450 1 %

Liquor ratio 100:1

The dyebath was prepared at 50 ⁰ C, the temperature raised at 2°C/min to 100 ⁰ C and held at this temperature for 30 minutes.

The results are shown in Figure 2.

It can be seen that there was almost no dye uptake by the pure polypropylene, whereas the semi-synthetic filaments containing modified wool powder of the invention were dyed. This illustrates how the semi-synthetic filament is dyeable by a conventional wool dye, whereas pure polypropylene is not. Accordingly, the heat stabilised wool powder did not degrade during the melt extrusion process and was able to take up the wool dye.

Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.