Treatment Of Textile Fabrics

Abstract

Textile fabrics comprising not less than 70% by weight of cellulose are treated with solutions of one or more silicon compounds in liquid ammonia. Cellulose molecules are crosslinked by the treatment, producing good wrinkle resistance and good water retention capacity.

Description

This invention relates to a process for treating a textile fabric which comprises applying a certain silicon compound or a mixture of silicon compounds to the fabric and subsequently drying the fabric.

It is known to treat textile fabrics comprising cellulosic fibers with liquid ammonia. This is typically done in the case of textile fabrics which are to be cured in the moist state.

It is likewise known to treat cellulosic fabrics with cellulose crosslinkers in order that the wrinkling characteristics of the ready-produced articles may be beneficially influenced. For this, the fabrics are typically processed on a pad-mangle in the course of a finishing process. The padding liquor is normally an aqueous solution or dispersion. This solution or dispersion will comprise one or more cellulose crosslinkers and also, if appropriate, further desired ingredients such as softeners for example.

Known cellulose crosslinkers include N-methylol compounds. These do indeed lead to good crosslinking results, but may be considered problematical because they include formaldehyde as a by-product or release by-produced formaldehyde at elevated temperature or in the course of storage. Prior artisans have searched for alternative crosslinkers which neither contain formaldehyde nor release it in the course of processing. They found that silanes can also be used to crosslink cellulosic fibers.

Processes utilizing silane cellulose crosslinkers are known. For instance U.S. Pat. No. 3,055,774, EP-A 563 961 and EP-A 401 668 describe the treatment of cellulose or cellulose derivatives with functional silanes. The silane is used in the form of an aqueous composition in all of these processes.

It has been determined that the crosslinking of cellulosic articles with aqueous systems comprising silanes does not always lead to optimal crosslinking results with regard to, for example, crease recovery, water retention capacity and so on. Moreover, certain reactive silanes cannot even be used to crosslink via aqueous systems since they will react with water or their cellulose reactivity is less than optimal in aqueous systems. These kinds of reactive silanes include, for example, silanes in which alkoxy groups are attached to the silicon atom. Specifically these silanes will be desirable for use as crosslinkers because of their cellulose reactivity.

The present invention has for its object to provide a process for effective crosslinking of textile fabrics having an appreciable cellulosic fiber content. The process shall further be able to employ as crosslinkers even those silicon compounds which are instable or less than optimally reactive in aqueous systems.

We have found that this object is achieved by a process for treating a textile fabric having a cellulosic fiber content in the range from 70% to 100% by weight with a solution in liquid ammonia of a silicon compound or of a mixture of silicon compounds, which process comprises applying this solution to the textile fabric and then drying the fabric,

wherein at least one of the silicon compounds used conforms to one of the formulae (I) to (IV)

where

all R radicals are independently hydrogen or an alkyl radical having 1 to 4 carbon atoms,

all R¹ radicals are independently an alkyl radical having 1 to 18 carbon atoms or phenyl,

the R² radical is a radical of the formula (V) or of the formula (VI)

where Ep is the univalent radical derived from ethylene oxide or is an epoxycyclohexyl radical, preferably 3,4-epoxy-1-cyclohexyl,

n is from 2 to 4,

a is from 1 to 3,

b is 3−a,

c is from 1 to 4, preferably 2,

d is 1 to 5,

e is from 1 to 4, preferably 1 or 3,

t is from 1 to 3,

y is from 1 to 3, preferably 1, and

t+y is from 2 to 4.

The process of the present invention is for treating textile fabrics having a cellulosic fiber content in the range from 70% to 100% by weight. The textile fabrics contemplated include wovens, knits and nonwovens. Wovens are preferred.

The cellulosic fiber content of the textile fabrics ranges from 70% to 100% by weight. When the cellulosic fiber content is less than 100%, the remainder may consist of synthetic fibers such as polyester or polyamide for example. Cellulosic fibers may consist of natural cellulose such as cotton for example or else of regenerated cellulose.

Textile fabrics treated by the process according to the present invention can be further processed into garments for example.

The process of the present invention has a number of advantages:

a) high crosslinking effectivity, frequently higher than crosslinking with the same silicon compounds in an aqueous medium.

b) can utilize even silanes which are highly cellulose reactive but which cannot be employed in the form of aqueous systems since they lack stability or reactivity in aqueous systems.

c) where the textile fabric is in any case to be treated with liquid ammonia it is frequently possible to save a processing stage, namely a separate operation to apply a cellulose crosslinker, since the crosslinker has already been applied (in the form of a solution in liquid ammonia).

On the other hand, it will be understood that a separate finishing operation may be carried out nonetheless, for example when further products in the form of aqueous solutions or dispersions are to be applied after the fabric has passed through the process of the present invention. Such products may include softeners, fluoropolymers or flame retardants, well known to those skilled in the textile-finishing arts.

d) a customary moist cure can be omitted after the process of the present invention has been carried out. It is thus preferable not to carry out a moist cure after the process of the present invention. On the contrary, very good crosslinking results are already provided by the present invention's process after drying with or without curing. This can be ascertained by means of the hereinbelow described determination of the wrinkle properties via determination of the wet crease angle.

e) the process of the present invention can be carried out without using products which contain formaldehyde or release it at elevated temperature.

In the process of the present invention, the identified textile fabrics are treated with a solution in liquid ammonia of a silicon compound of the hereinbelow described type. A mixture of silicon compounds can be used in place of a single silicon compound. At least one of the silicon compounds used shall conform to one of the hereinbelow illustrated formulae (I) to (IV). Preferably, all silicon compounds used fall under one of these formulae; that is, preferably no silicon compound is present which does not conform to any of the formulae (I) to (IV), but amino-functional polysiloxanes or other softeners can also be present in the solution in liquid ammonia. However, all employed silicon compounds and other softeners have to be readily soluble in liquid ammonia.

The applying of the ammoniacal solution to the textile fabric can be effected by methods known in the textile industry. Application by means of a bath, for example on a pad-mangle where the fabric is dipped into a solution of the desired silicon compound in liquid ammonia, is particularly suitable. The residence time of the textile fabric in the ammoniacal solution will normally be about 20 seconds to 20 minutes, but it can also be longer. This is followed by squeezing off in a known manner.

The solution of the defined silicon compound or of the mixture of silicon compounds at the time of application to the fabric is preferably at a temperature in the range from −60° C. to −40° C. This temperature range shall apply irrespectively of which application method is used. The amount of silicon compound in the ammonia solution is normally about 0.01 to 3 parts by weight, and preferably 0.1 to 0.7 part by weight, per 100 parts by weight of ammonia. These numerical statements relate to the total amount of all silicon compounds used which fall under one of the formulae (I) to (IV).

It is particularly advantageous and therefore preferable when the solution of the silicon compound or compounds in liquid ammonia further comprises a catalyst. Suitable catalysts provide an increased degree of crosslinking and hence better effects with regard to the crease resistance of ready-produced textiles and/or its durability. Sterically hindered amines such as for example diazabicyclo[2.2.2]octane (DABCO) or 4-dimethylaminopyridine (4-DMAP) are particularly suitable for use as catalysts. The amount of catalyst added is preferably in the range from 1.0% to 3% by weight, based on the total amount of silicon compounds of the formulae (I) to (IV) present in the ammoniacal solution.

The textile fabric has to be dried after the ammoniacal solution has been applied to it. Known drying apparatuses can be used. Drying is normally done at a temperature in the range from 60° C. to 180° C. and preferably from 80° C. to 150° C., and is carried on until ammonia, water and any alcohol formed have been removed. This normally requires a drying time of about 5 to 30 minutes. Water or alcohol are formed in the crosslinking reaction with OH groups on the cellulose when silicon compounds are used in which OH or OR groups are attached to silicon atoms.

It is frequently of advantage to Sanforize the textile fabric before it is dried. Sanforizing is a process of controlled compressive shrinkage applied to textile material, described for example in K. Peter, H. K. Rouette, Grundlagen der Textilveredelung, 13th edition, dfv Deutscher Fachverlag 1989, Frankfurt/Main, in particular pages 718 to 721.

After the textile fabric has been dried it may, if desired, be remoistened with water.

In one preferred embodiment of the process according to the present invention the textile fabric is cured after it has been dried, in particular when the drying temperature is below 130° C. Curing in this sense is a treatment at elevated temperature, for example in the range from 130° C. to 180° C. and preferably in the range from 140° C. to 170° C., for a period from 2 to 10 minutes. Curing can be used to increase the number of bonds which form between the cellulose and the reactive silicon compounds.

At least one of the silicon compounds used for the process of the present invention shall conform to one of the formulae (I) to (IV)

In these formulae

• • all the R radicals are independently hydrogen or an alkyl radical having 1 to 18 carbon atoms. Preferably, all the R radicals present are each an alkyl radical having 1 to 4 carbon atoms. This alkyl radical may be linear or branched. More preferably, all the R radicals are independently a methyl or ethyl group.
  • all the R′ radicals are independently an alkyl radical having 1 to 18 carbon atoms or unsubstituted phenyl. Preferably, all the R′ radicals are each either methyl or ethyl.
  • the R² radical is a radical of the formula (V) or of the formula (VI)

• • Ep is the univalent radical derived from ethylene oxide, i.e., the radical formed on removing a hydrogen atom from the formula for ethylene oxide (oxirane), or an epoxycyclohexyl radical, preferably 3,4-epoxy-1-cyclohexyl

n is from 2 to 4,

a is from 1 to 3,

b=3−a,

c is from 1 to 4, preferably 2,

d is from 1 to 5,

e is from 1 to 4, preferably 1 or 3,

t is from 1 to 3,

y is from 1 to 3, preferably 1, and

t+y is from 2 to 4.

It has been determined that optimal crease resistance results in many cases when c=2.

All these silicon compounds contain 2 or more reactive groups capable of reacting with the OH groups of cellulose, if necessary at elevated temperature. The result of this reaction is a crosswise linking together of cellulose chains which improves crease resistance.

Silicon compounds or silanes of the formulae (I) to (IV) and their preparation are known from the prior art, for example from the references cited at the beginning and from EP-A 1 199 339, or are preparable by processes known to one skilled in the art, for example by reaction of halosilanes with alcohols. Furthermore, silicon compounds of the formulae (I) to (IV) are commercially available, for example from Wacker, Germany.

The process of the present invention provides textile fabrics which have excellent properties with regard to creasing/wrinkling and water retention capacity, these properties being very durable to storage and laundering operations.

An instrument to determine the crease recovery angle wet (also known as wet crease angle) is described in Melliand Textilberichte, Vol. 39, No. 5, pages 552-554. This instrument can be used to determine the creasing/wrinkling characteristics of textile fabrics. The values of crease recovery angle wet which are reported hereinbelow in Examples 1a) to 1d) are based on determinations in accordance with this Melliand reference.

The samples were prepared as follows for this determination:

Woven fabric samples 2 cm×1 cm in size were placed in an aqueous solution containing 1 g/l of wetting agent (sodium salt of an alkylnaphthalenesulfonate). After 5 minutes, the samples were removed, laid on a plastics rail, folded and loaded with 500 g weight for 3 minutes. The weight was then removed for 3 minutes before the crease recovery angle was measured.

The invention will now be illustrated by examples.

EXAMPLES 1a) to 1d)

25 ml of ammonia are condensed in an apparatus at −40° C. or −60° C., 0.1 ml of alkoxysilane is added, and the contents of the apparatus are mixed until homogeneous. The identity of the alkoxysilane was varied in various experiments and is stated in tables 1 to 4. A hindered amine catalyst was added in some experiments. A woven fabric is then added, removed again after a defined period and warmed to room temperature. After the ammonia has evaporated off, the fabric is dried in a drying cabinet with or without curing. The woven fabric used was 100% cotton in all Examples 1a) to 1d).

The experimental conditions of Examples 1a) to 1d) are tabulated below. A different silicon compound (alkoxysilane) was used in each of these 4 examples. Where a catalyst was used as well, its amount was 2.5% by weight, based on the silicon compound, in each case.

EXAMPLE 1a)

TABLE 1
0.1 ml of γ-glycidoxypropyltriethoxysilane in 25 ml of ammonnia
Residence		Ammonia	Drying (T) and	Crease
time in		temperature	curing (K)	recovery angle
ammonia	Catalyst	[° C.]	conditions	wet [°]
30	s	—	−40	10 min 110° C. +	71
				5 min 150° C.
				(T + K)
5	min	DABCO	−40	10 min 110° C.	75
				(T)
5	min	DABCO	−40	10 min 110° C. +	82
				5 min 150° C.
				(T + K)

EXAMPLE 1b)

TABLE 2
0.1 ml of 1,2-bis(methoxydimethylsilyl)ethane in 25 ml of ammonia
				Crease
Residence		Ammonia	Drying (T)	recovery
time in		temperature	and curing (K)	angle
ammonia	Catalyst	[° C.]	conditions	wet [°]
30	s	—	−40	10 min 110° C. (T)	71
30	s	—	−40	10 min 110° C. +	80
				5 min 150° C.
				(T + K)
1	min	—	−40	10 min 110° C. (T)	73
1	min	—	−40	10 min 110° C. +	84
				5 min 150° C.
				(T + K)
5	min	DABCO	−60	10 min 110° C. (T)	75
5	min	DABCO	−60	10 min 110° C. +	82
				5 min 150° C.
				(T + K)
5	min	DABCO	−40	10 min 110° C. (T)	72
5	min	DABCO	−40	10 min 110° C. +	80
				5 min 150° C.
				(T + K)

EXAMPLE 1c)

TABLE 3
0.1 ml of γ-glycidoxypropylmethyldiethoxysilane in 25 ml of ammonia
Residence				Crease
time in		Ammonia	Drying (T)	recovery
ammonia		temperature	and curing (K)	angle
[min]	Catalyst	[° C.]	conditions	wet [°]
5	DABCO	−40	10 min 110° C. +	76
			5 min 150° C. (T + K)

EXAMPLE 1d)

TABLE 4
0.1 ml of triethoxy(2,4,4-trimethylpentyl)silane in 25 ml of ammonia
Residence	Ammonia		Crease
time in	temperature	Drying conditions	recovery angle
ammonia	[° C.]	(T)	wet [°]
10 s	−40	10 min 110° C. (T)	72
1 min	−40	10 min 110° C. (T)	78
Higher “crease recovery angles wet” values mean improved crease recovery performance.

Claims

1. A process for treating a textile fabric having a cellulosic fiber content in the range from 70% to 100% by weight with a solution in liquid ammonia of a silicon compound or a mixture of silicon compounds, which process comprises applying this solution to the textile fabric and then drying the fabric, wherein at least one of the silicon compounds used conforms to one of the formulae (I) to (IV) where

(RO)nSi(R1)4-n  (I)

(RO)tSi(R1)4-t-y(R2)y  (II)

(R1)b(RO)aSi—(CH2)c—Si(OR)a(R1)d  (III) and

(RO)a(R1)b—Si—O[Si(R1)2]d—O—Si(R1)b(OR)a  (IV)

all R radicals are independently hydrogen or an alkyl radical having 1 to 4 carbon atoms,

all R1 radicals are independently an alkyl radical having 1 to 18 carbon atoms or phenyl,

the R2 radical is a radical of the formula (V) or of the formula (VI) —(CH2)e-Ep  (V) —(CH2)e—O—CH2-Ep  (VI)

where Ep is a univalent radical derived from ethylene oxide or is an epoxycyclohexyl radical,

n is from 2 to 4,

a is from 1 to 3,

b is 3−a,

c is from 1 to 4,

d is from 1 to 5,

e is from 1 to 4,

t is from 1 to 3,

y is from 1 to 3,

t+y is from 2 to 4.

2. A process according to claim 1, characterized in that a curing operation is carried out subsequent to the drying step.

3. A process according to claim 1, characterized in that the solution in the liquid ammonia comprises from 0.1 to 0.7 part by weight of silicon compound or compounds of the formulae (I) to (IV) per 100 parts by weight of ammonia.

4. A process according to claim 1, characterized in that the applying of the solution to the textile fabric is effected by a padding operation and at a temperature for the solution in the range from −40 to −60° C.

5. A process according to claim 1 4, characterized in that the textile fabric is Sanforized before being dried.

6. A process according to claim 1, characterized in that the solution in liquid ammonia further comprises a catalyst in an amount from 1% to 3% by weight, based on the total amount of silicon compounds of the formulae (I) to (IV) present in the solution.

7. A process according to claim 6, characterized in that the catalyst is a sterically hindered amine or a mixture of sterically hindered amines.

8. A process according to claim 7, wherein the catalyst is diazabicyclo[2,2,2]octane or 4-dimethylaminophydine.