IE42688B1 - Sheathed staple fibers - Google Patents

Abstract

1488776 Composite polyester fibres HOECHST AG 12 May 1976 [14 May 1975] 19546/76 Heading B5B The fibres comprise an inner core of a hydrophilic linear polyester and the outer core of a non-hydrophilic linear polyester. Preferably the hydrophilic linear polyester is a block copolymer of from 90-20% by wt. relative to the polyester of polyethylene terephthalate and from 10 to 80% of a polyalkylene glycol. The hydrophilic linear polyester may also contain by incorporation or co-condensation 5-20% by wt. relative to the salt free ester of an alkali metal salt or an alkaline earth metal salt of a sulphonic acid or an acidic phosphoric or phosphonic acid ester.

Description

This invention relates to sheathed staple fibers insisting of a non-hydrophilic linear polyester and a lydrophilic polyester.

Synthetic filaments and fibers of for example, lolyesters ahd polyamides, for example derived from :erephthalic acid and glycols, and from adipic acid and lexamethylene diamine or caprolactam, respectively, are very ridely used in the manufacture of woven and knitted fabrics of •arious kinds because of their advantageous textile properties However, certain improvements in these properties are desirable, for example Increased moisture absorption and yeability, and improved electrostatic behaviour, while laintainlng the favourable textile properties.

Thus, for example, the moisture absorption of olyethylehe terephthalate at 20°C and a relative humidity - 2 42688 of 65% amounts to about 0.4% by weight, and that of polyamides derived from caprolactam or hexamethylene diamine and adipic acid is about 4% by weight, but that of cotton is 8% by weight and that of wool 12% by weight.

Various attempts have been made to increase the water absorption of synthetic fibers, for example by impregnation or sizing with foreign substances. The substantial disadvantage of these processes is that the after-treatment agents may be washed or worn off.

In addition, impregnation of polyethers brings about no substantial increase in water absorption without simultaneous deterioration of the good thermal and mechanical properties (British Patent Specification No. 956,833).

The great disadvantage of the modification,for example, of polyesters by adding a sulfonated polyalkyleneglycol, as proposed in German Auslegeschrift No. 2,019,458, is that reactive terminal groups such as —CI^Cl, -CH=CH2 and -CH-CHO \/ c which are present in the modification agent cause decomposition or heavy discolouration of the polyester in the melt.

Attempts have been made to obtain the desired improvement by means of copolymers of polyester and polyethyleneglycol, with or without organic metal salt derivative, to be incorporated by condensation or dispersion (U.S. Patent 688 Specification No. 3,682,846).

Although the properties of a polymer may be altered as desired and in a profitable manner by cocondensation, the insufficient activity of the cocomponents is very disadvantageous. Therefore, relatively large amounts of these cocomponents have to be used, which cause deterioration of other desirable properties, for example, reduction of the required high melting point and clogging of the filaments, so that the corresponding shaped articles are of lower overall quality.

These difficulties which occur during processing of known block copolyesters of polyethyleneglycol with or without cocondensed or dispersed organic metal salt derivatives can be prevented by spinning sheathed filaments containing a modified component in the sheath and a polymer having good mechanical properties such as polyethylene terephthaiate, in the core.

Sheathed filaments made, for example, from a block copolyester of polyethylene terephthaiate and polyethylenejlycol in the sheath and unmodified polyethylene terephthaiate in the core are distinguished by an increased fater absorption compared to unmodified polyethylene terephthaiate.

Sheathed filaments containing the modified component in the sheath are readily wetted by water and lisplay favourable electrostatic behaviour. The considerable reduction of the melting point and the altered crystallization behavior, however, cause clogging of the iheathed filaments on spinning the modified component per se .n the sheath. When the modified component is spun as the 43688 core, no clogging of the continuous filaments. occurs, although the excellent wetting power and the favourable electrostatic behaviour are then lost.

These problems which occur in all cases where, for example, hydrophilic, polyglycol-containing surfaces are present, have resulted in modification of the construction of the shaped articles rather than modification of the raw material (Albrecht, Textil-Praxis Int. 29 (1974) 1713; 5. Int. Makrom. Symp. Interlaken 6/7, June '74).

The present invention seeks to eliminate the above disadvantages and to provide textile articles which are simple to manufacture and which exhibit properties, especially improved moisture absorption.

In accordance with the present invention, there are provided sheathed staple fibers containing a non-hydrophilic linear polyester and a hydrophilic linear polyester, the core being formed exclusively by the hydrophilic linear polyester.

Preferred fibers in accordance with the present invention are those in which the hydrophilic linear polyester is a block copolymer of from 90 to 20% by weight, relative to the hydrophilic linear polyester, of polyethylene terephthalate, and from 10 to 80% by weight, relative to the hydrophilic linear polyester, of a polyalkyleneglycol.

Especially preferred fibers are those in which the hydrophilic linear polyester contains from 5 to 20% by weight, relative to the salt-free hydrophilic polyester, of an alkali metal salt or an alkaline earth metal salt of a sulfonic acid or an acidic phosphoric or phosphonic acid ester, the salt being cocondensed or incorporated into the polyester.

Other especially preferred fibers are those in which 8 ;he hydrophilic core contains from 5 to 30% by weight, relative to the core, of a disperse polyalkyleneglycol with blocked terminal groups. More especially preferred are those Ln which the hydrophilic linear polyester is a block ropolymer of from 90 to 20% by weight, relative to the lydrophilic linear polyester, of polyethylene terephthalate, md from 10 to 80% by weight, relative to the hydrophilic Linear polyester, of a polyalkyleneglycol, preferably jolyethyleneglycol or a (block) copolymer of ethylene oxide md propylene oxide containing from 10 to 80% by weight of ithylene oxide units, the block copolymer containing from 5 ;o 20% by weight, relative to its salt-free weight, of a :ocondensed or incorporated alkali metal salt or alkaline iarth metal salt of a sulfonic aoid or an acidio phosphoric >r phosphonic acid ester.

The sheathed staple fibers of the present invention ire especially suitable for the manufacture of bidimensional textile articles. They are distinguished by increased moisture ibsorption, excelleht wettability and favourable electrostatic lehavior.

This is especially surprising, Since, for example, for ι titer of 2.7 dtex, a mean density of the fibers of 1.38 g/ ic and a cut length of the staple fibers of 38 mm, the ratio >f the surface area having the expected hydrophilic properties it the cut only, to the remaining surface is 1:10000 if the lass ratio sheath/core is 1:1.

By sheathed filaments and fibers, there are therein :q be understood those filaments and fibers where a core lomponent is completly wrapped by a sheath component having a >arallel longitudinal axis. The core component may be composed 43688 of one or more strands which may be symmetrically or asymmetrically arranged within the sheath.

In accordance with the present invention, the sheath is composed of a conventional linear polyester, for example polyethylene, polybutylene or poly - 1,4 - cyclohexane - dimethyl terephthalate, or of a conventional copolyester. By linear polyesters, there are herein to be understood those polyesters containing up to 3% by weight of a branching multi-functional alcohol or acid component. These polyesters and copolyesters which have not been specially modified with respect to water absorption are non-hydrophilic. Hydrophilic polyesters, on the other hand, are those polyesters having a moisture absorption of many times the usual value of about 0.4% by weight.

Preferred polyesters having hydrophilic properties are those of terephthalic acid containing polyalkyleneglycols having blocked terminal groups, such as polyethyleneglycol or a copolymer of ethylene oxide and propylene oxide, with sulfonic acid salts, or salts of acidic phosphoric acid esters, or salts of acidic phosphonic acid esters, dispersed therein in a concentration of from 5 to 30% by weight.

Also preferred are block cocondensates of from 90 to 20% by weight of polyethylene terephthalate, relative to the hydrophilic component, and 10 to 80% by weight of polyalkyleneglycol or a polyalkyleneglycol copolymer having reactive condensable terminal groups, preferably polyethyleneglycol, advantageously having a molecular weight of from 200 to 20000, preferably from 1500 to 4000.

A copolycondensate of 75% by weight of polyethyleneglycol having a molecular weight of 3000 and 25% by weight of 388 >olyethylene terephthalate, has a softening point of about .76°C and no filament-forming properties, but it may be spun is the core material combined with polyethylene terephthalate is the sheath material in sheathed filament spinning techniques, yielding filaments or fibers having very good lechanical properties.

Better results still with respect to increased moisture bsorption and good wettability and electrostatic behaviour are btained using block copolymers containing from 90 to 20% by eight of polyethylene terephthalate and from 10 to 80% by eight of polyalkyleneglycol, preferably polyethyleneglycol, aving a molecular weight of from 1500 to 4000, when from 5 to 0% by weight, relative to the saltfree block copolymer, of an lkali metal salt or alkaline earth metal salt of a sulfonic Cid, an acidic phosphoric or phosphonic acid ester are added o the block cocondensate. When containing bifunctional eactive groups, the metal salt derivatives are cocondensed, he reactive groups must be capable of being added to the ondensate in large amounts without acting as regulator, imiting chain growth. Metal salt derivatives incapable of eing cocondensed are dispersed in the block copolymer as a atrix according to known methods. The antistatic properties at ow relative humidity obtainable by combining polyethyleneglyol and metal salt derivative, are especially good.

The block polymers can be prepared in known manner by sit polycondensation; conventional additives such as dulling jents (TiOj), thermo-oxidation stabilizers, optical brighteners, Lameproofing or anti-spilling agents can be added.

The sheath, as supporting component, may also be sdified in this manner and it may be dyeable without a carrier. - 8 42688 The polymers are spun to sheathed filaments in the usual equipment and the filaments are processed to staple fibers according to known methods.

Because of their favourable mechanical and antistatic behavior, and especially their excellent wettability and improved moisture absorption, such staple fibers are suitable per se or may be blended with other fibers, for example cotton, to give articles worn next to the skin their special microclimate, for example under-wear and shirts.

The following Examples illustrate the invention.

Example 1 (Comparative Example) This example shows the difference of wettability which results from incorporating the hydrophilic polymer into the core or the sheath of a sheath/core bicomponent filament. For this purpose, the following polymers are spun: 1) an unmodified polyethylene terephthalate (PET) having a specific viscosity of 0.79, measured on a 1% by weight solution in a mixture of phenol/tetrachloroethane, mixing ratio 3:2, at 25°C, and 2) a polyethylene terephthalate modified with 5% by weight of sodium - 5 - sulfoisophthalic acid dimethyl ester (SIM) and 20% by weight of polyethyleneglycol (PEG) having a molecular weight of 3000? the modified PET has a specific viscosity of 0.76, measured as indicated above.

Both polymers are spun in a known bicomponent spinning apparatus in such a manner that in one case the unmodified polymer is in the core and the modified polymer in the sheath of a sheath/core filament (filament No. 1, Table, - 9 688 Jo. 1) and in the other case the modified polymer is in the core and the unmodified polymer in the sheath (filament No.

!, Table, No. 2).

The spinning rate per component is 32 g/minute, the Iraw-off rate 1500 m/min; the nozzle has 32 holes. After spinning, both filaments are drawn 2.59 times their length on i Zinser 16 S type draw-twister over a godet having a temperature of 90°C and a hot plate having a temperature of _60°C. The bobbins containing filament No. 1 display clogged sections which adversely affect the processing properties. ?rom filaments Nos. 1 and 2, respectively, a knitted fabric is lanufactured the sizing agent of which is eliminated by means cf methanol.

The water absorption at 65% of relative humidity and !0°C is 1.5% for both filaments, the water retention capacity, letermined according to German Industrial Standard DIN 53 814, Ls about 9%.

When a knitted fabric as described above and liberated :rom the sizing agent is fitted in a stenter in such a manner chat it is neither stretched nor loosened, and when a drop cf about 50 mm of distilled water is applied to the fabric cy means of a pipette and the time is measured which passes :rom the moment of application of the drop to that of its ibsorption, a measure for the wettability is thus Set in a nost simple manner. By absorption, there is to be understood ι state where the water has spread out over the textile naterial as over a blotting-paper and is not lying any more on :op of it in the form of a drop.

When the above wetting test is carried out using the initted fabric manufactured from filament No. 1, the water - 10 42638 drop is absorbed after less than 3 seconds; in the case of the knitted fabric manufactured from filament No. 2, the drop is not yet absorbed even after 30 minutes but it is lying on top of the fabric without showing any signs of alteration.

Both knitted fabrics behaved differently also in a test where, at 23°C and a relative humidity of 30%, the friction charge (Volts/cm) is measured by means of a field-intensity meter after rubbing the sample against a knitted fabric of Nylon-6 and subsequently the time is determined which has passed until half of the friction chargq is released. This halfvalue time is 22 seconds in the case of the knitted fabric from filament No. 1, and more than 30 minutes in that of the knitted fabric from filament No.2.

Example 2.

The following example shows the difference of wettability of usual polyethylene terephthalate staple fibers and the hydrophilic staple fibers of the invention. A bicomponent filament (filament No. 3) in sheath/oore arrangement is spun; the core consisting of the modified PET described in Example 1, and the sheath of the unmodified PET described also in Example 1. The spinning rate of each component is 13 g/ minute, the nozzle contains 32 holes, the draw-off rate is 1500 m/minute. The spun filament is drawn 2.27 times its original length; the filament being forwarded first through a steam tunnel and then over a hot plate having a temperature of 160“C. The drawn filament is mechanically crimped in a stufferbox and cut into fibers having a length of 38 mm. The fibers are spun in known manner to yield a yarn which is processed to a jersey.

When this jersey liberated from the sizing agent is ubjected to the wetting test indicated in Example 1, the rop of water is absorbed by the textile material in less han 3 seconds. The half-value time of electrostatic discharge s 22 seconds.

The jersey is used for the manufacture of undershirts isplaying cotton-like, comfortable wearing properties.

For a comparison there is manufactured an identical arsey from usual unmodified PET staple fibers (Table, No. 4) aving the same individual titer, length of cut and yarn □nstruction. The wetting test showed the drop not being □sorbed even after 30 minutes and still lying on top of the Loth in a nearly unchanged shape. The half-value time of the Lecttostatic discharge is longer than 30 minutes.

Example 3.

A bicomponent sheath/core filament is spun, the )lymer of the core of which is an unmodified PET having a iecific Viscosity of 0.79. The polymer of the sheath consists ι a PET containing 20% by weight of a cocohdensed polyethylene glycol having a molecular weight of 3000. The modified PET is a specific viscosity of 1.09. The spinning rate of each imponent is 32 g/minute, the draw-off rate 1500 m/minute, the >zzle has 32 holes. The filament (Table, No. 5), displaying .ogged sections on a bobbin, is drawn 2.59 times its original :ngth over a godet having a temperature of 90°C and a hot .ate having a temperature of 160°C and subsequently processed ι a knitted fabric. The knitted fabric is liberated from the .zing agent by means of methanol.

When the fabric is wetted in the manner as described l Example 1, the drop is absorbed in less than 3 seconds.

Because of the missing salt of sulfoisophtalic acid, the half-value time of the electrostatic discharge is longer than 30 minutes at 30% of relative humidity and 20°C.

Xn a further test, the polymers of the core and the sheath are interchanged, that is, the modified polymer is now in the core (Table, No. 6). This filament does not show any clogged sections, and a knitted fabric manufactured from the drawn filament, after having been liberated from the sizing agent by means of methanol, has no absorbing effect on wetting? after 30 minutes, the drop is still lying on top of the textile material in a nearly unchanged shape.

A bicomponenfc filament is then spun containing in the core the modified polymer as described above in this Example and the unmodified polymer also described in this Example in the sheath. Manufacturing dates: spinning rate per component 13 g/minute, draw-off ,rate 1500 m/minute, drawing rate 1:2.27 through steam tunnel and subsequently over a hot plate having a temperature of 160°C, The drawn filaments are mechanically crimped in a stufferbox according to known methods, cut into fibers having a length of 38 mm and spun to form a yarn. A jersey manufactured from tHis yarn (Table, No. 7) and liberated from the sizing agent absorbed the drop in less than 3 seconds on wetting; the half-value time of electrostatic discharge was longer than 30 minutes.

Example 4.

A sheath/core bicomponent fiber yarn (Table, No. 8) is manufactured as follows: The core consists of a PET modified by cocondensation of 10% by weight of a polyglycol inving a molecular weight of 3000 and 104 by weigh I. of the sodium salt of sulfoisophthalic acid; the specific viscosity Ls 0.73. The sheath is an unmodified PET having a specific ziscosity of 0.79. The spinning rate per component is 23 g/ ninute, the draw-off rate 1500 m/minute and the number of loles of the nozzle 32.

The filament is drawn 2.7 times through a steam ;unnel and over a hot plate having a temperature of 160°C, she drawn filament is crimped in a stufferbox, cut into a :iber length of 38 mm and processed to a staple fiber yarn. A jersey manufactured therefrom, after having been liberated 'rom the sizing agent by means of methanol, absorbs a drop >f Water ih less than 3 seconds in the Getting test.

Example 5.

A fiber yarn (Table, No. 10) is manufactured iccording to Example 4, but as polymer for the core, a PET laving a specific viscosity of 1.58 is used which is modified rith 75% by weight of polyethyleneglycol (molecular weight 1000). Because of the large amount of polyglycol, the melt of ihe core polymer has a very low viscosity and is spinnable inly together with the sheath polymer, an unmodified PET having ι specific viscosity of 0.79 The spinning rate of the core component is 15 g/minute, :hat of the sheath component 30 g/minute, the draw-off rate is .500 m/minute and the nozzle has 32 holes. The filament is Irawn 2.4 times thrdugh a steam tunnel, crimped in an airlooled stufferbox, cut to a length of 38 mm and processed to : staple yarn. A jersey manufactured therefrom and liberated 'rom the sizing agent absorbs the water drop after less than - 14 4268 seconds in the wetting test.

Example 6.

A bicomponent fiber (Table, No. 9), the core of which consists of a PET, specific viscosity 0.95, modified with 5% by weight of sodium-paraffin sulfonate (NaPS) having 13 to 18 carbon atoms in the chain and on the average up to 2 sulfonate groups randomly distributed in the molecule, and with 20% polyethyleneglycol (molecular weight 3000), and the sheath of which consists in a PET (specific viscosity 0.79) is manufactured.

The spinning rate per component is 13 g/minute, the draw-off rate is 1500 m/minute, the nozzle has 32 holes.

The filament is drawn 2.27 times through a steam tunnel and subsequently over a hot plate having a temperature of 160°C, crimped in a stufferbox, cut to a length of 38 mm and processed to a fiber yarn. A jersey manufactured therefrom and liberated from the sizing agent absorbs the drop in less than 5 seconds in the wetting test; the half-value time of the electrostatic discharge is 1.4 minutes.

Example 7.

A sheath/core bicomponent fiber (Table, No. 11) is manufactured: the core is a PET to which 5% by Weight of sodium· paraffin-sulfonate having 13 to 18 carbon atoms in the chain and on the average up to 2 sulfonate groups randomly distributed in the molecule are added and which has a specific viscosity of 0.87. The sheath is an unmodified PET having a specific viscosity of 0.79. The fiber is manufactured under the spinning and drawing conditions as indicated in Example 6. A 5688 jersey manufactured from these fibers, after having been liberated from the sizing agent, has a half-value time of electrostatic discharge of more than 30 minutes, and in the wetting test,·the drop is absorbed after less than 3 seconds. Ο »5 O rd •Ρ β I φ β rd Μ Μ id τι β rd ω Μ 0) Q ft Md ϋ 0 •rd P Φ td g +> •3 Ul Φ P 0 01 fi fi Φ +> Itf 2 Ο X! CM O rd φ o CM co «π ω A > Φ -rd τί Ud Φ rd x; td P xi β 0 •rd P Qi — fi β ε o 0 -d CO co U) P V A Ul U5 Ul P P P fi ID fi fi Φ ki Φ Φ £ Φ g g id P (0 io rd rd •d •rd ft Md Md Si W ω xi t)P P »n id + Φ Cd Xi ft Ul ft tfp n CM + H Eh ft M ft ft w P a ----------- Φ β 0 D. s £ H 0 Ul ϋ •rd φ dP ft ρ in 0 d- □ o ft ft dP o CM + H &H W M ft ft CM Ο CM ΓΟ Λ - Ο ro ω ν Α υι ω Μ Μ φ φ Λ Λ •Η Ή m μη Εη W ft S Η U1 m + ϋ Μ ft ο CM + Εη μ ft OOO cn co co AAA ε O = ,co ro cn v a v 05 P +5 β β Φ Φ rd •Η ϋ « ft Λ» ο CM + &Η EM Eh WWW ft ft ft CM TP rd O ro A O co A co V tn Φ Λ •d Md Ed W ft tp V CO V Ul ki Φ Λ •rd Md Eh M ft s ω H ft ω £ dP o dP rd in + O 0 O O ft ft ft w ft ft ft ft dP dP dP dP o o O o CM CM rd CM + + + + Eh Eh EH EH w w ft M ft ft ft ft PET+75% PEG PET fibers υι Ρ β Φ β Ο 61 Ο υ ο β ο ΕΗ W ft

Claims (6)

1. Sheathed staple fibers containing a nonhydrophilic linear polyester and a hydrophilic linear polyester, the core being formed exclusively by the hydrophilic linear polyester.

2. Sheathed fibers as claimed in claim 1, wherein the hydrophilic linear polyester is a block copolmer of from 90 to 20% by weight, relative to the polyester, of polyethylene terephtalate, and from 10 to 80% by weight, relative to the polyester, of a polyalkyleneglycol.

3. Sheathed fibers as claimed in claim 1 or claim 2, wherein the hydrophilic linear polyester contains incorporated or cocondensed therein from 5 to 20% by weight, relative to the salt-free polyester, of an alkali metal salt or an alkaline earth metal salt of a sulfonic acid or an acidic phosphoric or phosphonic acid ester.

4. Sheathed fibers as claimed in any one of claims 1 to 3, wherein the core contains from 5 to 30% by weight, relative to the core, of a dispersed polyalkyleneglycol having blocked terminal groups.

5. Sheathed staple fibers as claimed in claim 1 substantially as described in any one of Examples 2 to 7 herein.

6. A textile material containing sheathed staple fibers as claimed in any one of claims 1 to 5.