GB1585399A

GB1585399A - Polyester filaments with a high water retention capacity

Info

Publication number: GB1585399A
Application number: GB5396277A
Authority: GB
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1976-12-29
Filing date: 1977-12-28
Publication date: 1981-03-04
Also published as: FR2376231B1; JPS607067B2; JPS5386831A; FR2376231A1; IT1090368B; DE2659263A1

Description

(54) POLYESTER FILAMENTS WITH A HIGH WATER RETENTION CAPACITY (71) We BAYER AKTIENGESELLSCHAFT, a body corporate organised under the laws of the Federal Republic of Germany, of 509 Leverkusen, Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to porous polyester fibres and filaments with an increased water retention capacity, and to a process for their production.

For a whole range of applications, for example for underwear or bed linen, it is of considerable importance to have available textiles of synthetic fibres which show cotton-like properties in their behaviour with respect to moisture.

It has now been found that an improvement in the water retention capacity of polyester filaments can be obtained by adding high molecular weight water-soluble polyamides to terephthalate polyesters before the spinning process and washing them out again during the aftertreatment of the filaments to form pores.

The present invention provides microporous polyterephthalate fibres and filaments having a moisture absorption capacity of at least 1 % at 65 % relative humidity and a water retention capacity of at least 15 Wo, obtainable by adding to filament-forming terephthalate polyesters, of which at least 90 mole % consist of structural elements with the following general formula:

in which R represents a straight-chain alkylene radical containing from 2 to 8 carbon atoms, a cycloalkylene radical or the radical:

and up to 10 mole % consist of structural elements corresponding to the formula::

C t=C-(O-CH2-CH2)n-00 and/or t 9 SO t in which SOjM R is as defined above, n is an integer of greater than 10, and M represents an alkali metal radical at least one water-soluble aliphatic polyamide having a relative solution viscosity are of from 0.5 to 4.0 (as measured on a solution of 1 g of the polyamide in 100 ml of cresol at a temperature of 25"C) in a quantity of from 1 to 20 % by weight, based on the polyester, in the melt, spinning the resulting mixture as a physical mixture to form filaments, and completely or partly washing out the added polyamide with water during the aftertreatment.

The terephthalate polyesters used may be both homopolycondensates, such as for example polyethylene terephthalate, polybutylene terephthalate or poly-1,4-cyclohexylene dimethylene terephthalate, and also copolyesters modified with 5-sulphoisophthalic acid in the acid component and/or with polyethylene glycol in the diol component. According to the invention, it is preferred to use polyesters having relative solution viscosities are of from 1.1 to 4.0 (as measured on a solution of 1 g of substance in 100 ml of o-chlorophenol at 25"C before treatment with the polyamide).

Preferred water-soluble aliphatic polyamides are, for example, polycaprolactams or polyamides of hexamethylene diamine and adipic acid which contain either from 800 to 1800, more especially from 800 to 1500, or from 1000 to 1800 millivals of sulphonate groups per kilogram in the form of structural elements corresponding to the formula:

or up to 6000 and preferably from 2000 to 6000 millivals of tertiary amino groups per kilogram of polyamide in the form of structural elements corresponding to the formula:

The relative solution viscosities frel of these additions should be in the range from 0.5 to 4.0 (as measured on solutions of 1 g of the polyamide in 100 ml of cresol at 25"C).

In one preferred embodiment, the porous polyester filaments according to the invention are produced by adding to a fully condensed polyester melt just before the spinning process a defined quantity of at least one water-soluble "basic" or "acid polyamide concentrate" produced by methods known per se at a temperature of from 220 to 280"C through a metering screw installed just prior to the spinneret, followed by intensive mixing for 3 to 4 minutes, and spinning the resulting mixture into filaments. This procedure effectively precludes transamidation-transesterification reactions so that the polyester and polyamide are present in physical admixture and no deterioration can be detected in the properties of the filaments by comparison with normal polyesters.

The "basic polyamides" are produced in known manner by polycondensing aliphatic polyamines, such as for example bis-y-aminopropyl piperazine. with an aliphatic dicarboxylic acid, such as for example adipic acid, together with a lactam, such as for example E-caprolactam or hexamethylene diammonium adipate, in the melt in the absence of oxygen in an inert gas atmosphere. Depending upon the required molecular weight, one of the components, either the diamine or the dicarboxylic acid, is used in a quantity exceeding the stoichiometrically necessary quantity.

The water-soluble polyamides containing high concentrations of sulphonate ("acid polyamide concentrates") are also obtained in known manner, for example by polycondensing the bis-alkali metal salt of N,N'-bis-(2-sulphonatobenzyl)-hexamethylene diamine, adipic acid and caprolactam or hexamethylene diammonium adipate in the melt in an inert gas atmosphere. In this case, too, either the acid component or a diamine component is used in excess as a chain terminator, depending upon the molecular weight selected.

These "concentrates" are added in quantities of from 1 to 20 % by weight and preferably in quantities of from 1 to 10 % by weight, based on the polyester. The size of the addition is limited by the spinnability of the melt mixture and is also determined by the required porosity or the water retention capacity.

After the spinning process, the water-soluble addition present in the fibres may be completely or partly removed from the filaments, according to requirements, during drawing of the filaments in water and in a following washing process to leave pores behind in the filaments. However, it is also possible initially to wash the filaments with water and then to draw them. The further aftertreatment may be carried out by known methods, such as crimping, drying, preparing and cutting.

The filaments produced by the process described above are microporous, the average pore diameter being in the range of from about 0.5 to 5 > , depending upon the addition selected, its molecular weight and the drawing and washing conditions. The water retention capacity of the filaments and fibres according to the invention is critically dependent upon the type and quantity of water-soluble polyamide added and also upon the aftertreatment conditions.

In addition to their high water retention capacity, the fibres according to the invention also show good fibre properties, such as high tensile strength and elongation at break.

Water retention capacity is an important physical parameter so far as clothing is concerned. The effect of a high water retention capacity is that textiles worn close to the skin are able to keep the skin relatively dry despite increased perspiration. Accordingly, clothing worn close to the skin produced from textiles with a high water retention capacity has a snug feel and is considerably more comfortable to wear.

The polyesters according to the invention may, of course, contain standard known catalysts, discoloration inhibitors, heat stabilisers, optical lighteners, antistatic agents, flameproofing agents, dyes, pigments and inactive fine particles.

Determinatidn of water retention capacity (WR): Water retention capacity is determined in accordance with DIN Specification 53 814 (cf.

Melliand Textilberichte 4 1973, page 350).

The fibre samples are immersed for 2 hours in water containing 0.1 % by weight of wetting agent. Thereafter the fibres are centrifuged for 10 minutes with an acceleration of 10,000 m/sec.2 and the amount of water retained in and between the fibres is gravimetrically determined. In order to determine their dry weight, the fibres are dried at 105"C until they have a constant moisture content. The water retention capacity (WR) in % by weight is:

where mf = weight of the moist fibres m,r = weight of the dry fibres Determination of moisture absorption capacity (MA): The moisture absorption of the fibres, based on their dry weight, is gravimetrically determined. To this end, the samples are exposed for 24 hours to a climate of 21"C/65 % relative air humidity. In order to determine the dry weight the samples are dried at 105"C until constant in weight. The moisture absorption (MA) in % by weight is:

where mf = weight of moist fibres at 21"C/65 % relative humidity mtr = dry weight of the fibres.

The relative solution viscosities llrel quoted in the following Examples were measured at 25"C on solutions of 1 g of the substance in 100 ml of o-chlorophenol.

The invention is further illustrated by the following Examples. The parts by weight quoted are to parts by volume as kilograms are to litres.

Example a: Production of a water-soluble polyamide with sulphonate groups based on AH-salt.

20.52 parts by weight of the internal salt of N,N'-bis-(2-sulphonatobenzyl)hexamethylene diamine:

together with 7.83 parts by weight of hexamethylene diamine, 17.25 parts by weight of adipic acid, 3.60 parts by weight of sodium hydroxide, 8.35 parts by weight of AH-salt, 0.75 part by weight of 75 % phosphorous acid and 45 parts by weight of water, are introduced under nitrogen into a polycondensation apparatus. The condensation apparatus is then closed and the mixture of components is heated with stirring to 2000C. When an internal pressure of 10 atms guage has been reached, the polycondensation apparatus is slowly vented and, at the same time, the temperature is increased to 2850C while nitrogen is passed over.After 2 hours' stirring and passing over of nitrogen under these conditions, the internal pressure is reduced to 15 Torr over a period of 1 hour and condensation is continued for another 2 hours. The melt is then spun off by way of a drying belt and the polymer strands obtained are granulated. The homogeneous colourless concentrate can be characterised as follows: Tire = 1.10 (lg in 100 ml of m-cresol at 250C) water content = 0.02 % softening range = 195 - 210 C sulphur content: 1725 millivals of sulphonate groups per kg of polyamide.

Example b: Production of a water-soluble polyamide containing sulphonate groups based on caprolactam.

A mixture of 34.20 parts by weight of the internal salt of N,N'-bis-(2-sulphonatobenzyl)hexamethylene diamine, 14.25 parts by weight of disodium adipate, 1,25 parts by weight of adipic acid, 5300 parts by weight of E-caprolactam and 100 parts by weight of water are introduced into the polycondensation apparatus described in Example (a) while nitrogen is passed over. After the apparatus has been closed, the mixture of components is heated with stirring to 200"C so that an internal pressure of approximately 12 atms gauge is reached.

The polycondensation apparatus is then slowly vented, nitrogen is passed over and the temperature is increased to 270"C. After a reaction time of 1.5 hours under these conditions, the internal pressure is reduced to 12 Torr over a period of 1 hour, and condensation is continued for 2.5 hours. The viscous melt is then spun off by way of a drying belt and granulated. The granulate is colourless and homogeneous and has the following properties: Tire = 1.31(1 g in 100 ml of m-cresol at 25"C) water content = 0.01 % softening range = 125 - 140"C sulphur content: 1498 millivals of sulphonate groups per kg of polyamide.

Example c: Production of a water-soluble polyamide containing tertiary amino groups based on AH-salt.

34.60 parts by weight of N,N'-bis-(3-aminopropyl)-piperazine adipate, 3.50 parts by weight of AH-salt, 0.58 part by weight of hexamethylene diamine and 0.03 Part by weight of phosphorous acid are introduced into the apparatus described in Example (a) and heated to 1900C while nitrogen is passed over. Stirring is then commenced and the temperature is increased to 250"C. Condensation is over after about 3 hours. The basic polyamide is spun off and granulated. It shows the following properties: Tire = 1.58 (1 g in 100 ml of m-cresol at 250C) water content = 0.01 % softening range = 160-175"C nitrogen content: 5750 millivals of tertiary amino groups per kg of polyamide.

Example d: Production of a water-soluble polyamide containing tertiary amino groups based on caprolactam.

44.0 parts by weight of bis-(3-aminopropyl)-piperazine, 29.2 parts by weight of adipic acid and 31.8 parts by weight of caprolactam are heated with stirring under nitrogen to 250"C in the polycondensation apparatus described in Example (a). Condensation is carried out for 4 hours under these conditions. The melt is then run off from the vessel and size-reduced. The substantially colourless basic concentrate has the following properties: Tire = 0.95 water content = 0.03 % softening range = 125 - 1300C nitrogen content: 4150 millivals of tertiary amino groups per kg of polyamide.

Examples 1 - 8 Production of porous polyterephthalate fibres based on polyethylene terephthalate.

The water-soluble polyamide concentrates described in Examples (a) - (d) are added to and mixed as follows with a polyethylene terephthalate melt. The resulting mixture is spun as a physical mixture and processed into porous fibres: The particular polyamide concentrate is melted in a three-zone extruder (1* = 360 mm, d** = 30 mm). (* 1 = length) (** d = diameter). The nominal temperatures are adjusted to 230, 240 and 250"C so that the temperatures in the product amount to around 210, 240 and 250"C. The extruder delivers the concentrate to a gear pump which meters it into a main melt of polyethylene terephthalate having a relative viscosity Tire of 1.70. Depending upon the quantity to be introduced, its drive it fixedly coupled with that of a pump delivering the main melt. The metering of a constant proportion of concentrate is ensured in this way.

After metering, the two melts are mixed for about 3 minutes in a dynamic Wiemann mixer at a nominal temperature of 280 + 10 C. The homogeneous mixture is then delivered to a spinneret and spun into a tow. The tow is then initially drawn for about 2 seconds in a ratio of from 1:3.6 to 1:4.5 in water heated to 850C. It is then after-drawn in a heating duct for about 6 seconds at a steam temperature of from 120 to 1600C. This is followed by washing for 3 to 5 minutes in boiling water under slight tension. The tow is then crimped by the stuffer-box process, fixed, brightened and cut. The porous polyester fibres thus obtained having high light-scattering values show the following data, depending upon the type and quantity of the addition (see Table 1).

TABLE 1 Type Fibre data and Residual quantity Individual Tensile Elongation Boiling- #rel of Water re- Moisture content of of denier strength at break induced the tention absorption polyamide in the addition [dtex] [cN/dtex] [%] shrinkage filaments capacity [%] fibres [%] [%] [%] 10 % from Example a 17.3 2.83 37.2 0.3 1.64 25.0 3.8 2.7 5 % from Example a 17.2 3.21 61.0 0.4 1.69 17.3 2.8 0.2 10 % from Example a 3.3 2.95 38.6 0.4 1.60 27.1 3.6 1.8 3 % from Example a 3.3 3.05 40.1 0.4 1.58 16.4 2.5 0.9 10 % from Example b 16.9 2.80 40.4 0.6 1.60 19.5 5.2 3.1 10 % from Example c 17.0 3.31 45.8 0.8 1.57 21.4 3.4 4.1 12 % from Example d 16.8 2.75 46.3 0.9 1.68 26.4 2.0 1.0 Comparison Example 17.2 5.1 55.0 1.1 1.62 5.5 0.3 without any addition Examples 9 - 12 Production of porous polyterephthalate fibres based on poly-1,4-cyclohexylene dimethylene terephthalate.

As described in Examples 1 to 8, the water-soluble polyamide concentrates of Examples (a) to (d) are added in the same way in different quantities to a polymer melt of poly-1,4-cyclohexylene dimethylene terephthalate having a relative viscosity tires of 1.81 just before the spinning process. The physical mixture is then delivered to a spinneret where it is spun into a corresponding tow. In contrast to Example 1, the tow is drawn only once for about 6 seconds in a ratio of from 1:2.75 to 1:3.3 in a heating duct at steam temperatures of from 120 to 1600C. This is followed by washing for 3 to 10 minutes in boiling water under slight tension, after which the tow is crimped, fixed, brightened and cut. Examples of the data of the porous fibres obtained by this process are set out in Table 2.

TABLE 2 Fibre data Type and Individual Tensile Elongation Boiling- #rel of Water Moisture Residual content quantity denier strength at break induced the retention absorption of polyamide in the of addition [dtex] [cN/dtex] [%] shrink- filaments capacity [%] fibres age [%] [%] [%] 10 % from Example a 3.3 1.5 35.2 0.7 1.62 23.6 3.2 4.2 10 % from Example b 17.4 1.5 37.0 0.9 1.70 21.8 4.0 2.6 5 % from Example d 17.1 1.8 37.8 0.9 1.66 18.4 1.8 0.8 Comparison Example without any addition 16.9 2.5 45.1 0.8 1.69 4.8 0.2 - Examples 13 - 18 Production of porous polyterephthalate fibres based on copolyesters.

Two polyethylene terephthalate copolyesters were used as the base polyesters.

By co-condensation of ethylene glycol with terephthalic acid dimethyl ester and 2.96 % by weight of the sodium salt of 5-sulphoisophthalic acid dimethyl ester, type A has a sulphonate concentration of 100 millivals/kg of polyester. The relative viscosity Tire of this copolyester amounts to 1.54.

Type B was polycondensed in known manner by the co-condensation of ethylene glycol, terephthalic acid dimethyl ester and 10 % by weight of polyethylene glycol having an average molecular weight Mn of 2000. The relative viscosity Tire amounts to 1.48.

In exactly the same way as described in Examples 1 to 8, the water-soluble polyamide concentrates of Examples (a) to (d) are added in different quantities to the two copolyesters A and B just before the spinning process, followed by spinning. The tows obtained are after-treated and processed into fibres under the same conditions as in Examples 1 to 8.The technological data of the porous hydrophilic fibres obtained are set out in Tables 3 and 4. TABLE 3 Fibre data of copolyester A Type and Individual Tensile Elongation Boiling #rel of Water Moisture Residual quantity denier strength at break induced the retention absorption content of of addition [dtex] [cN/dtex] [%] shrink- filaments capacity [%] polyamide in age [%] the fibres [%] [%] 10 % from Example a 17.1 2.98 39.2 0.8 1.45 28.4 4.3 3.5 8 % from Example d 3.5 3.61 45.8 0.7 1.41 25.9 4.0 1.2 Comparison Example without any addition 17.4 5.00 56.1 0.9 1.50 4.9 0.8 - TABLE 4 Fibre data of copolyester B Type and Individual Tensile Elongation Boiling- #rel of Water Moisture Residual quantity denier strength at break induced the retention absorption content of of addition [dtex] [cN/dtex] [%] shrink- filaments capacity [%] polyamide in age [%] the fibres [%] [%] 10 % from Example a 16.8 2.55 38.8 1.1 1.40 27.9 4.8 2.8 10 % from Example c 3.8 2.99 44.5 0.9 1.45 29.0 5.1 4.4 Comparison Example without any addition 17.0 4.31 52.2 1.4 1.48 4.1 0.9 -

Claims

WHAT WE CLAIM IS:

1. Microporous polyterephthalate fibres and filaments having a moisture absorption capacity of at least 1 % at 65 % relative humidity and a water retention capacity of at least 15 %, obtainable by adding to filament-forming terephthalate polyesters, of which at least 90 mole % consist of structural elements corresponding to the general formula:

in which R is as defined above, n is an integer of greater than 10, and M represents an alkali metal radical, at least one water-soluble aliphatic polyamide having a relative solution viscosity Tire of from 0.5 to 4.0 (as measured on a solution of 1 g of the polyamide in 100 ml of cresol at 25"C) in a quantity of from 1 to 20 % by weight, based on the polyester, in the melt, spinning the resulting mixture as a physical mixture to form filaments. and completely or partly washing out the added polyamide with water.

2. Filaments and fibres as claimed in Claim 1, wherein they have a relative solution viscosity Tire! of from 1.1 to 4.0 (as measured on a solution of 1 g of substance in 100 ml of o-chlorophenol at 25 C).

3. Filaments and fibres as claimed in Claim 1 or 2, wherein the water-soluble polyamide is a sulphonate-group-containing polycaproamide containing from 800 to 1500 millivals of sulphonate groups per kilogram of polyamide.

4. Filaments and fibres as claimed in Claim 3, wherein the polyamide comprises structural elements corresponding to the formulae:

5. Filaments and fibres as claimed in Claim 1 or 2, wherein the water-soluble polyamide is a sulphonate-group-containing polyamide of hexamethylene diamine and adipic acid containing from 100 to 1800 millivals of sulphonate groups per kilogram of polyamide.

6. Filaments and fibres as claimed in Claim 5, wherein the polyamide comprises structural elements corresponding to the formulae:

7. Filaments and fibres as claimed in Claim 1 or 2, wherein the water-soluble polyamide is a polycaproamide containing from 2000 to 6000 millivals of tertiary amino groups per kilogram of polyamide.

8. Filaments and fibres as claimed in Claim 7, wherein the polyamide comprises structural elements corresponding to the formulae:

9. Filaments and fibres as claimed in Claim 1 or 2, wherein a water-soluble polyamide of hexamethylene diamine and adipic acid containing from 2000 to 6000 millivals of tertiary amino groups per kilogram of polyamide is used.

10. Microporous polyester filaments and fibres as claimed in Claim 1, substantially as hereinbefore described with reference to any of the Examples.

11. A process for the production of porous polyterephthalate filaments and fibres having a moisture absorption capacity of at least 1 % at 65 % relative humidity and a water retention capacity of at least 15 %, comprising the steps of adding to a filament-forming terephthalate polyester, of which at least 90 mole % consist of structural elements corresponding to the general formula:

in which R is as defined above n is an integer of greater than 10, and M represents an alkali metal radical, at least one water-soluble aliphatic polyamide having a relative solution viscosity Tirci of from 0.5 to 4.0 (as measured on a solution of 1 g of the polyamide in 100 ml of cresol at 225"C) in a quantity of from 1 to 20 % by weight, based on the polyester, in the melt; spinning the resulting mixture as a physical mixture to form filaments; and completely or partly washing out the added polyamide with water.

12. A process as claimed in Claim 11, wherein the polyamide comprises structural elements corresponding to the formulae:

13. A process as claimed in Claim 11 or 12, wherein the polyester filaments have a relative solution viscosity Tire of from 1.1 to 4.0 (as measured on a solution of 1 g of substance in 100 ml of o-chlorophenol at 250C).

14. A process as claimed in Claim 11, substantially as hereinbefore described with reference to any of the Examples.

15. Polyester filaments and fibres produced by a process as claimed in any one of Claims 11 to 14.

16. A textile article comprising polyester filaments and fibres as claimed in any one of Claims 1 to 10 and 15.