The present invention relates to the use of a linear synthetic polymer having a molecular weight of from 510 ³ to 110 ⁷ to improve the strength and elongation, to reduce the fibrillation and to regulate the water absorption properties of a cellulose shaped body, derived from a dissolution of cellulose in a tertiary amine oxide. The linear synthetic polymer is preferably a polyethylene, a polyethylene glycol, a polyacrylate, a polymetacrylate or a copolymer between an acrylate or a metacrylate and another monomer.

It is well-known to produce cellulose fibres and other formed products by preparing cellulose solutions in tertiary amine oxides, like N-methyl morpholine-N-oxide (NMMO) , optionally containing minor amount of water, extrud¬ ing the cellulose solutions through spinnerets and coagulat¬ ing the fibres formed in an aqueous bath followed by at least one washing bath. See for example the US patents No

3 447 939, 3 447 956 and 4 211 574. In AT 401 063 B, it has also been suggested to use non-aqueous fluids in the bath. The cellulose used in these processes has usually a poly¬ merisation degree of not lower than 200 and preferably not lower than 400. The cellulose fibres manufactured from the cellulose-NMMO system according to the above mentioned system normally exhibit a tensile strength of about 15 cN/tex and an elongation at break of about 4-8%. The cellu¬ lose fibres intended for clothing purposes must have con- siderably higher levels of elongation at break, namely over

10% combined with an improved tensile strength. Another disadvantage of cellulose fibers produced by the NMMO system is the too high tendency to fibrilate and to form small balls on the fabric surface, which is also known as pilling. Furthermore, in the Patent Publication DD-A1-218 121, it has been observed that air gap between the spinneret and the coagulation bath may be reduced if a polyethylene glycol

having a molecular weight of 1000 is present in a NMMO cellulose solution. The US Patent 5 047 197 suggests to add a polyethylene glycol having a molecular weight of from about l.l milion to about 4.5 ilion to a cellulose dis- solved in a tertiary amine oxide to improve the flow rate through a spinning nozzle. WO 96/14451 discloses the use of a polyaikylene imine derivate to stabilize a shaped body derived from cellulose regenerated by the amino-oxide pro¬ cess and WO 86/05526 discloses the possibility to add a number of polymers to a dissolution of lignocellulose materials in a tertiary amino oxide. Thus, none of these references presents a solution of the disadvantages earlier mentioned.

The US Patent No 4 246 221 discloses a NMMO process for the manufacture of cellulose fibres with improved strength. However, the application of the fibres in fabric industry is rather limited due to their wet fibrillation tendency.

Therefore, one object of the present invention is to essentially improve the general properties, like dry strength, wet strength, elongation and to reduce the fibril¬ lation of a cellulose shaped product produced by a tertiary amine oxide process in order to make the fibres more useful, e.g. for textile fabrics. Another object of the invention is to be able to re¬ gulate and to control the water absorption properties of the product, such as retention, absorbed water amounts, and absorption speed.

According to the present invention, it has been found that the above mentioned objects are achieved by using a linear synthetic polymer having a molecular weight of from 5 10 ³ to l'lO ⁷ , preferably from 1 10* to 1 10 ^s , in a shaped body, obtained by dissolving the cellulose and the synthetic polymer in a tertiary amine oxide, like NMMO, optionally containing up to 20% water based on the amount of the terti¬ ary amine at a temperature from 70°C to 130°c, preferably from 80°C to 120°C, forming a shaped body of the dissolution

and coagulating the shaped body in at least one bath under the removal of the tertiary amine oxide. The formation of the shaped body is performed in a conventional manner, for example by extruding the dissolution through a spinneret. In addition to the polymers, modifiers utilized in the produc¬ tion of viscose fibres and cellulose fibres from the terti¬ ary amine oxide process, such as cationic, anionic, nonionic and amphoteric surfactants; complexing agents; and solubi- lizers, like polyethylene glycols with molecular weight be- low 1-000; may be present in the dissolution of the polymers or in the coagulation bath. The amounts of modifiers in the dissolution are usually from 0.2 to 5% by weight of the dis¬ solution and from 50 to 1 000 ppm of the bath. The fluid in the coagulation bath is usually a water solution, but other fluids, like polyethylene glycols, may be used.

The incorporation of the synthetic linear polymer with the cellulose results in a composite product with un¬ expected positive effects. Thus, the ability of the new products to fibrilate is essentially decreased, while the tensile strength and the elongation at break are essentially increased. Suitable synthetic polymers to be used in the present invention are polyaikylene, such as polyethylene and copolymers of ethylene and propylene; polyaikylene glycols, such as polyethylene glycols, polypropylene glycols and polyaikylene glycols, where the alkylene groups are a mix¬ ture of at least two different alkylene groups containing 2, 3 or 4 carbon atoms, preferably 2 and 3 carbon atoms; poly- acrylates and polymetacrylates and the copolymers of acry- lates or metacrylates with other monomers, such as a copoly- mer between acrylic acids and acrylamides.

In order to obtain the desired properties it is essential that the polymer weight and the structure of the polymer make it possible to dissolve the polymer under the condition earlier mentioned. By dissolving it is here under- stood that the liquid formed may have the form of a true solution, a icroemulsion or a homogeneous emulsion. The polyalkylenes and other copolymers, which are not directly

soluble in the tertiary amine oxide cellulose solutions of the present invention, have to be in liquid form at a temperature below 130°C.

The polyalkylenes are preferably polyethylenes and have molecular weights from 110* to 110 ^s . The polyaikylene glycols preferably have a molecular weight of from 110 to 510 ^s , and most preferably from 310 ⁴ to 210 ^s . The polyacry- lates or polymetacrylates or copolymers of acrylates or met- acrylates with other monomers preferably have a molecular weight of from 1'10 ⁴ to no ⁶ and most preferably from 410 ⁴ to 5'10 ^s . The molecular weight of the cellulose is usually from 510 ⁴ to 2-10 ^s , preferably from 710 ⁴ to 1.510 ^s .

The present invention also compasses a cellulose shaped body derived from a dissolution of cellulose in a tertiary amine oxide, characterized in, that it contains a) a cellulose and b) based on the weight of the cellulose, from 0.2-20% by weight of a linear synthetic polymer select¬ ed from the group consisting of a polyaikylene having a molecular weight of from 510 ³ to HO ¹ ; a polyaikylene gly- col having a molecular weight of from 3 0 to 210 ^s ; and a polyacrylate or a polymetacrylate or a copolymer between an acrylate or a metacrylate and another omomer having a mole¬ cular weight of from 510 ³ to 110 ⁷ . Suitably the synthetic polymer is a polyethylene with a molecular weight of from 510* to 210 ^s or a copolymer between an acrylic acid and an acrylamide, the copolymer having a molecular weight of from 4'10* to 510 ⁵ . The polyaikylene glycol is suitably a poly¬ ethylene glycol.

The present invention is further illustrated by the following working examples.

Example 1

An amount of 15 parts by weight of a spruce cellulose (DP 700) was dissolved in 71.5 parts by weight of NMMO and 13.5 parts by weight of water together with an acrylic- acrylamide copolymer (MW 120 000) in the amounts stated in Table 1. Fibres were formed by extruding the dissolution at 115°C through a spinneret with orifices of 160 μ in dia-

meter and a length/diameter ratio of 4:1. The distance be¬ tween the spinneret and the coagulation bath was 20 mm and the temperature in the bath was 20°C. The process was con¬ ducted with a take-up speed of 45 m/min and 15-fold total drawing ratio. The linear density of the fibres were 3 dtex. The coagulated fibres were washed thoroughly with water to remove remaining NMMO solvent and then dried. Their physical and mechanical properties, such as strength, water absorp¬ tion, water retention, elongation and fibrillation degree were determined. Fibrillation degree was determined by use of microscopic method described in Chemiefasern Textilind. 43(95) , 876(1993) .

The following results were obtained.

Table 1

Example % Copoly¬ F i b r e p r o p e r t i e s mer by weight Strength Elonga¬ Fibril¬ Water Reten¬ cellulose cN/tex tion lation absorp¬ tion

% degree tion % %

1 - 16.5 4.2 6.0 14.4 86.8

2 1% 18.2 9.5 5.2 14.3 94.6

3 3% 20.7 9.2 4.1 14.4 96.6

4 5% 28.9 10.5 4.3 14.5 95.8

The cellulose fibres containing a minor amount of the copolymer have in comparison with the prior art cellulose fibre a high strength, high elongation and reduced fibrilla¬ tion. Although the water absorption is about equal between the different fibres the retention is unexpectedly increased for the fibre according to the present invention.

Example 2

The process described in Example 1 was repeated but the copolymer was replaced by 3% or 5% by weight of a poly¬ ethylene glycol having a molecular weight of 53 000. A number of physical and mechanical properties of the fibres

obtained was determined. The following results were obtain¬ ed.

Table 2

Example % poly¬ Fibre properties ethylene glycol by

Strength Elonga¬ Wet Fibril¬ Reten¬ weight of cN/tex tion strength lation tion cellulose

% cN/tex degree %

1 3 23.2 11.4 17.4 4.3 98.3 2 5 24.0 11.1 19.4 3.8 120.6

3 16.5 4.2 14.2 6.0 86.8

From the results it is evident that properties like strength, elongation, fibrillation degree is essentially improved by the presence of the synthetic polymer. The im- provment in reducing the fibrillation degree is also im¬ portant. Moreover, the retention of water is increased, which depends on the incorporation of the hydrophilic poly¬ ethylene glycol polymer.

Exempel 3

The process described in Example 1 was repeated but the copolymer was replaced by a low molecular weight of polyethylene (MW 48 000) with a flow temperature of about 100 to 105°C. The physical and mechanical properties of the fibres obtained were determined.

The following results were obtained.

Table 3

Example % Poly¬ Fibre properties ethylene by weight

Strength Elonga¬ Fibrilla¬ Retention of cellu¬ tion tion lose cN/tex % degree %

1 16.5 4.2 6.0 86.8 2 1 27.5 11.8 4.6 76.4 3 3 21.2 10.6 3.8 72.1

4 5 25.6 8.4 3.2 68.9

From the results it is evident that presence of poly¬ ethylene has a remarkable positive effect on properties like strength, elongation and fibrillation. Moreover, the reten¬ tion of water is lowered by the incorporation of the hydro¬ phobic polyethylene polymer.