EP3892772A1 - Flame retardant finishing of textile fabrics with polycondensation products - Google Patents

Abstract

A polycondensation product which comprises repeat units I and (IIa and / or IIb) and has an average molar mass in the range from 400-5000 g / mol, in which each R ¹ independently of one another, is used for the flame retardant finishing of textile fabrics for hydrogen, -CH ₂ OH, -CH ₂ OCH ₃ or -CH ₂ OCH ₂ CH ₃ stands; each R ² independently of one another for -CH ₂ OH, - CH ₂ OCH ₃ or -CH ₂ OCH ₂ CH ₃; and each Y independently of one another represents a single bond or -O-CH ₂ -; wherein the molar ratio of I to the sum of IIa and IIb is in the range from 1.4 to 0.9 to 0.9 to 1.4, on the textile fabric; and cross-links the polycondensation product on the textile fabric.

Description

The present invention relates to a method for the flame retardancy of textile fabrics, in which a nitrogen- and phosphorus-containing polycondensation product is applied to a textile fabric and is crosslinked thereon. The present invention also relates to a textile fabric with flame-retardant properties which can be obtained by this process.

The subsequent finishing and treatment of textiles, nonwovens and paper with flame retardants is a process that is frequently used in industry. Flame retardants are applied to the cellulose structure by impregnation and remain on the fibers after drying. If they are not fixed or made insoluble by a subsequent reaction, they can be removed again by immersion or washing. This can be explained as products that are applied from aqueous solution usually have a high affinity or solubility in water.

If, on the other hand, you want to achieve resistance to watering and washing, the flame retardant must be fixed. In principle, this is possible through insoluble deposits, reactive connections or the build-up of networks due to heat treatment.

Effective flame retardants for textiles are organic compounds containing phosphorus and nitrogen that reactively bind to cellulose fibers.

In the Pyrovatex process, textiles are treated with N-methylol-dialkylphosphonopropionamides. This causes a reaction with the cellulose fiber at temperatures of 150-170 ° C and a very acidic pH of 2 to 4.

At the same time, however, the warm, acidic conditions cause partial hydrolysis of the cellulose, which leads to a loss of strength and is a major disadvantage of the process. Another disadvantage is that the reaction is an equilibrium reaction, which means that around 50% of the flame retardant molecules do not bind to the cellulose and are therefore not washable. In addition, exact compliance with the reaction conditions is necessary, which places high demands on the systems and the precision of the equipment.

In the U.S. 2,809,941 describes that tetrakis (hydroxymethyl) phosphonium chloride (THCP) or tris (hydroxymethyl) phosphine oxide (THPO) can be converted to polymers with nitrogen compounds such as urea, urea derivatives or melamine. Textiles are impregnated with a solution of the monomers and dried. The monomers polymerize at an elevated temperature. Monomeric tetrakis (hydroxymethyl) phosphonium chloride and tris (hydroxymethyl) phosphine oxide are hazardous substances and should only be handled in chemical plants. The reaction of THPC with the nitrogen compounds does not take place directly, but only via the intermediate stage of trihydroxymethylphosphine (THP), with formaldehyde being split off. The reaction of THPO is much slower than that of THP with amines, melamine or urea urea. A complete implementation of THPO on the fiber material is therefore not to be expected.

Registration CN 107629248A describes the condensation of tris (hydroxymethyl) phosphine oxide with phosphorus oxychloride, producing linear and cyclic oligomers which are further reacted with melamine.

In the so-called Proban® process, textile fabric is first impregnated with THPC and dried. The tissue is then gassed with ammonia. THPC reacts with the ammonia gas to form an insoluble, three-dimensional polycondensate. Following the ammonia treatment, the goods are subjected to a rinsing, oxidation and washing process in order to remove the gevom to convert the trivalent state into the odorless pentavalent state. The disadvantage of the process is that special systems for gassing with ammonia gas are required. The implementation represents a safety, cost and environmental problem for the processing companies. All by-products must then be washed out. However, the textiles treated according to the Proban® process have a high degree of rigidity. Therefore one tries to counteract the stiffening by the subsequent addition of plasticizers as well as by sanforizing (roughening the surface). However, the Sanfor treatment means an additional work step and special systems. The disadvantage of the subsequent addition of plasticizers is that plasticizers are generally flammable if they evaporate when exposed to a flame and are ignited in the gas phase. Therefore, textiles with flame retardant treatment are very limited in the amount of plasticizer.

the WO 1988 / 002283A1 describes a process in which a prepolymer of urea and tetrakis (hydroxymethyl) phosphonium chloride is applied to a textile, the textile is gassed with ammonia and the ammoniated prepolymer is oxidized to form phosphine oxide.

The reaction products of THP, urea, formaldehyde and formaldehyde-ammonia adducts lead to the build-up of molecules with higher molar masses. However, this is not a controlled, reproducible structure, since, depending on the type of fiber, the migration stability of the individual components in the fiber and the concentration of the starting materials, reaction products with different amounts of nitrogen and phosphorus atoms and different nitrogen / phosphorus atomic ratios can arise. The different reaction products differ in their molecular weight, flame retardancy and also washing permanence, which can be seen in the average fixation rate of approx. 50%.

The one unpublished on the priority date of this application EP 19194436.2 describes a process for equipping absorbent substrates in which a reaction product of an aminoplast precondensate with tris (hydroxymethyl) phosphine oxide, which reaction product has free or etherified N-hydroxymethyl groups, is applied to the substrate; and crosslinking the reaction product on the substrate. With regard to an optimal flame retardant effect, the reaction product has a nitrogen / phosphorus atomic ratio of 4: 1 to 12: 1. Compared to other flame retardants, the flame retardant finish has the advantage, for example, that the coated textiles do not have to be rewashed.

The phosphorus- and nitrogen-containing flame retardants known from the prior art often have the disadvantage that they worsen the performance properties of flat textile structures. For example, these can lose their suppleness and stiffen, which among other things leads to a greatly reduced wearing comfort of the garments made from these fabrics or to poor processability of the fabrics, which, for. B. in the production of furniture or car covers is disadvantageous.

In addition, the flat structures finished with the known flame retardants frequently do not have satisfactory wash resistance. Frequently, the flat structures equipped with flame retardants give off formaldehyde afterwards, so that a rewash is necessary to reduce the formaldehyde in order to meet the requirements for the maximum formaldehyde content according to the Oekotex standards.

It was therefore an object of the present invention to provide an economical method for flame retardant finishing which gives textile fabrics a high level of flame protection while at the same time being comfortable to wear or having a pleasant grip. In addition, the treated textile fabrics should be environmentally friendly and meet the current Ökotex standards with regard to formaldehyde content.

1. (i) ein Polykondensationsprodukt, welches Wiederholungseinheiten I und (IIa und/oder IIb) umfasst und eine mittlere Molmasse im Bereich von 400-5000 g/mol aufweist,
   
   worin
   • jedes R¹ unabhängig voneinander für Wasserstoff, -CH₂OH, -CH₂OCH₃ oder - CH₂OCH₂CH₃ steht;
   • jedes R² unabhängig voneinander für -CH₂OH, -CH₂OCH₃ oder -CH₂OCH₂CH₃ steht; und
   • jedes Y unabhängig voneinander für eine Einfachbindung oder -O-CH₂- steht; wobei das Molverhältnis von I zur Summe von IIa und IIb im Bereich von 1,4 : 0,9 bis 0,9 : 1,4 liegt, auf das textile Flächengebilde aufbringt; und
2. (ii) das Polykondensationsprodukt auf dem textilen Flächengebilde vernetzt.

According to the invention, this object is achieved by a method for the flame retardancy of textile fabrics, in which one

1. (i) a polycondensation product which comprises repeat units I and (IIa and / or IIb) and has an average molar mass in the range of 400-5000 g / mol,
   
   wherein
   • each R ¹ independently represents hydrogen, -CH ₂ OH, -CH ₂ OCH ₃ or _{-CH 2} OCH ₂ CH ₃ ;
   • each R ² independently represents -CH ₂ OH, -CH ₂ OCH ₃ or -CH ₂ OCH ₂ CH ₃ ; and
   • each Y independently represents a single bond or -O-CH ₂ -; where the molar ratio of I to the sum of IIa and IIb is in the range from 1.4: 0.9 to 0.9: 1.4, applies to the textile fabric; and
2. (ii) the polycondensation product is crosslinked on the textile fabric.

At least some of the radicals R ^{1 are} preferably different from hydrogen.

It has surprisingly been found that the application properties of the treated textile fabrics can be controlled via the ratio of repeat units of the formula (I) to the sum of the repeat units (IIa and IIb). It is essential to the invention that the molar ratio of I to IIa and IIb is in the range from 1.4: 0.9 to 0.9: 1.4, preferably 1.2: 0.9 to 0.9: 1.2, in particular 1.1: 0.95 to 0.95: 1.1. Due to this narrowly defined molar ratio, it is possible to achieve high fixing rates, i.e. good wash resistance, while at the same time maintaining the suppleness of the textile. In further experiments, the inventors were also able to show that a deviation from this ratio leads to poorer performance properties. A 1: 2 or 1: 3 stoichiometry results in hard and lacquer-like finishes that have no textile character. In particular, the soft hand of the textile fabrics deteriorates. If, on the other hand, the sum of the repeating units (IIa and IIb) is used in a deficit of 1: 0.5, for example, the soft handle is retained, but the washing resistance (fixation rate) drops significantly.

The polycondensation product applied in step (i) according to the invention has a limited number of reactive N-methylol groups or etherified N-methylol groups. This avoids a high level of cross-linking and at the same time reduces the entry of bound formaldehyde.

According to the invention, the polycondensation product has an average molar mass in the range from 400-5000 g / mol. Due to its non-ionic character and its size, the polycondensation product can penetrate deeper layers of the textile fabric and then react with itself. In contrast to this, polycondensation products with many hundreds of repeating units are only able to penetrate the textile fabric with difficulty or not at all because of their size and shape. As with filtration, they stick to the surface of the textile fabric.

Another advantage of the method according to the invention is that only one component is applied. This allows it to penetrate evenly into the textile fabric. There is an identical stoichiometric ratio of nitrogen to phosphorus across all zones of the textile fabric and the N: P ratio cannot change due to migration. The good distribution of the components also ensures that overall less polycondensation product containing nitrogen and phosphorus can be applied to achieve good flame retardancy. When applying a 2-component system, where only one component has reactive N-methylol groups, premixing is regularly necessary. In addition, the two components can distribute and / or migrate differently on the textile fabric, so that unbound components can later be easily washed out, which in turn reduces the flame retardant finish.

Another object of the invention is a textile fabric with flame-retardant properties, obtainable by the method described in detail above and below.

Textile fabrics are to be understood as meaning all textile fabrics, regardless of their manufacturing process. Such fabrics are z. B. fabrics, knitted fabrics, knitted fabrics, tuftings, felts and nonwovens.

The polycondensation product used in step (i) can be obtained by reacting suitable amounts of tris (hydroxymethyl) phosphine oxide (THPO), formaldehyde and an amine / amide selected from urea, melamine or mixtures thereof. The N-hydroxymethyl groups formed can be etherified with methanol or ethanol. Alternatively, THPO can be reacted with an aminoplast precondensate in an aqueous medium at alkaline pH.

In the polycondensation product, the phosphorus-containing repeat units and the nitrogen-containing repeat units are covalently linked, so that a separation cannot occur on penetration, which would automatically result in poorer fixation.

In one embodiment, the polycondensation product contains only repeat units of the formulas (I) and (IIa). In a further embodiment, the polycondensation product contains only repeat units of the formulas (I) and (IIb).

Before application, the polycondensation product is preferably in the form of aqueous solutions with a solids content of 40-80% by weight. Aqueous solutions with this solids content are low-viscosity and easy to apply.

To improve the wetting behavior, the solution of the polycondensation product can contain wetting agents. Suitable wetting agents are anionic or nonionic surfactants, such as alkoxylated fatty alcohols, alkoxylated fatty acids, alkyl sulfates, alkoxylated alkyl sulfates, alkyl sulfosuccinates, alkoxylated alkyl sulfosuccinates, polyether-modified polysiloxane copolymers or alkyl phosphonate esters.

The crosslinking of the polycondensation product can take place with itself, the textile fabric and / or by reaction with reactive groups of the textile fabric.

This crosslinking takes place by heating to a temperature of 100 to 250 ° C. The speed of crosslinking depends not only on the temperature but also on the pH of the applied solution. To increase the storage stability, the polycondensation product is generally adjusted to a basic pH. The crosslinking of the polycondensation product, on the other hand, takes place preferably at neutral to acidic pH. Therefore, the polycondensation product becomes preferable treated with an acid, suitably before application to the substrate. Suitable acids are mineral acids such as phosphoric acid, phosphorous acid, sulfuric acid, sulfonic acids such as amidosulfonic acid, or organic acids such as acetic acid. Acid salts such as ammonium chloride can also be used to adjust the pH. The crosslinking temperature depends, among other things, on the temperature resistance of the textile fabric. In suitable embodiments, crosslinking is carried out at a temperature of 140 to 200 ° C. and a pH of 3.5 to 6.5, preferably 4 to 6, in order to complete the finishing of the textile fabric. When crosslinking under these conditions over a period of 10 to 40 minutes, preferably 20-30 minutes, ether bonds are converted into stable methylene groups (by reaction of two methyl groups), while the formaldehyde formed is used to add onto free NH groups in the crosslinked rearrangement product. As a result, the free formaldehyde content decreases overall. Depending on the duration of the treatment, the textile fabrics treated by the method according to the invention meet the Ökotex standard of product class 2, 3 or 4 of a maximum of 75, 150 and 300 μg / kg of free formaldehyde.

The amount of polycondensation product applied after drying is generally from 20 to 50% by weight, based on the sum of the weight of the polycondensation product and the flat textile structure.

It is known that cotton can be treated with silicon compounds to produce water-repellent and soft-feel effects. The silicon compounds are either bound covalently or merely adhesively attached. Non-covalent textile finishes show a low wash permanence. Equipment that is only deposited on the surface of the textile can be worn away by mechanical stress or the influence of surfactants in the washing process. The effects such as soft feel or water repellency are reset to the original level of the unfinished goods after a few washes.

In a further embodiment, at least one silicone is therefore applied to the textile fabric to improve wearing comfort and a soft feel. The at least one silicone can be linear or branched and alkoxylated and / or alkylated with terminal or lateral blocks. A suitable siloxane is, for example, pure polydimethysiloxane.

The at least one silicone preferably comprises a siloxane which has groups which are able to react with the N-methyl groups of the polycondensation product. Suitable groups which are able to react with the N-methol groups of the polycondensation product are primary amino groups, secondary amino groups, epoxy groups, etc. In particular, the at least one silicone comprises an aminosiloxane with primary and / or secondary amino groups. Usually the at least one silicone is applied as an aqueous emulsion such as a macroemulsion or microemulsion.

In another embodiment, the polycondensation product is crosslinked in the presence of the aminosiloxane. It is advantageous to apply the aminosiloxane to the textile fabric in a preceding step and then to apply the polycondensation product to the textile fabric in step (i). The reaction of the polycondensation product with the aminosiloxane leads to the formation of water-insoluble networks. Without being bound by theory, it is assumed that the non-polar plasticizer and the polar polycondensation product occupy other areas of the textile surface. However, there is overlap where the plasticizer and the polycondensation product form bonds, which increases the overall setting rate, the washing permanence and the grip. This gives textile fabrics with a soft handle, good fire protection and good wash resistance.

The polycondensation product and optionally the at least one silicone can be applied by any suitable method, e.g. by autoclaving, dipping, spraying or painting processes.

The method according to the invention is suitable for the flame retardant finishing of textile fabrics.

The textile fabrics treated according to the invention are, for example, nonwovens, woven fabrics, knitted fabrics or knitted fabrics, preferably woven fabrics. The textile fabrics can contain wool. In the context of the present invention, the term wool includes all coarse and fine animal hair. In particular, the textile fabrics comprise cellulose-containing fibers such as cotton, regenerated cellulose, hemp, flax, jute, sisal or mixtures thereof. The textile fabrics are preferably made entirely or predominantly of cotton and contain, for. B. 65 to 100% by weight cotton. The cotton can be native or regenerated cotton. If the textile fabrics contain other fibers in addition to cotton, it can be, for. B. synthetic fibers such as polyester or polyamide. The textile fabric containing cellulose can contain up to 50% by weight of polyester fibers. Also preferred are regenerated cellulose, such as viscose, modal, Tencel or Lyocell.

The method according to the invention is suitable for the flame retardant finishing of textile fabrics. A post-wash to remove unreacted polymers or oligomers and other by-products can advantageously also be dispensed with. In particular, the remaining proportion of formaldehyde is compared to processes from the prior art. The addition and reactive incorporation of plasticizers can greatly increase the soft handle, so that mechanical softening by roughening, such as Sanfor treatment, can be dispensed with. The equipment does not generate any corrosive properties in contact with metal parts, such as B. Brackets for fastening upholstery fabrics. The equipment gives a hydro-lift effect. Water is repelled on the surface, so that drying of the fabrics is simplified and the addition of water repellants is no longer necessary.

Another object is a flat textile structure obtainable by a method as described above.

The invention is illustrated in more detail by the following examples.

Example 1: Synthesis of a flame retardant consisting of repeat units of the formulas (I) and (IIb)

65.3 g THPO, 60 g melamine and 27.6 g paraformaldehyde were heated to 120 ° C. in a flask and heated at 110-120 ° C. for 10 minutes. The reaction mixture was cooled and dissolved in 100 g of methanol. The mixture was then refluxed at 65 ° C. for 2 hours. The mixture was then diluted with 150 g of water and a vacuum was applied in order to remove methanol. 244 g of a 52% strength by weight clear, colorless solution are obtained.

Example 2: Synthesis of a flame retardant consisting of repeating units of the formulas (I) and (IIa)

The procedure of Example 1 was repeated, but instead of 60 g of melamine, 28.5 g of urea were used. 221 g of a cloudy solution were obtained.

Example 3: Finishing cotton

Fabric made of 100% cotton was finished with the flame retardant from Example 1 using a dip-squeeze process at pH 5 and dried and crosslinked at various temperatures and periods of time.

Table 1 contains the formaldehyde content before washing and the fixing rates after washing. Table 1: temperature Time / minutes Edition Fix rate HCHO [µg / kg] 130 ° C 15th 24% 70% 100 ppm 130 ° C 30th 27% 79% 55 ppm 160 ° C 15th 29% 77% 45 ppm 160 ° C 30th 27% 81% 15 ppm 190 ° C 15th 29% 88% <10 ppm 190 ° C 30th 28% 91% <10 ppm

The flame retardant effect was determined optically and in accordance with the flame retardancy test DIN 4102B2. All finished samples passed the flame retardant test.

Comparative example 4:

Fabric made of 100% cotton was finished using a dip-squeeze process according to the procedure in Example 1, but a reaction product of a melamine-urea-formaldehyde precondensate with THPO in a molar ratio of 2: 1 was used instead of the flame retardant from Example 1. The fabric had a significantly harder feel compared to the fabric samples in Example 1.

Comparative example 5:

Fabric made of 100% cotton was finished using a dip-squeeze process according to the procedure in Example 1, but a reaction product of a melamine-urea-formaldehyde precondensate with THPO in a molar ratio of 0.5: 1 was used instead of the flame retardant from Example 1. The fixation rate dropped significantly.

Claims (12)

Process for the flame retardancy of textile fabrics, in which one (i) a polycondensation product which comprises repeat units I and (IIa and / or IIb) and has an average molar mass in the range of 400-5000 g / mol,

wherein each R ¹ independently represents hydrogen, -CH ₂ OH, -CH ₂ OCH ₃ or -CH ₂ OCH ₂ CH ₃ ; each R ² independently represents -CH ₂ OH, -CH ₂ OCH ₃ or -CH ₂ OCH ₂ CH ₃ ; and each Y independently represents a single bond or -O-CH ₂ -; where the molar ratio of I to the sum of IIa and IIb is in the range from 1.4: 0.9 to 0.9: 1.4, applies to the textile fabric; and (ii) the polycondensation product is crosslinked on the textile fabric. Process according to claim 1, wherein the crosslinking takes place at a temperature of 140 to 200 ° C and a pH of 3.5 to 6.5. Method according to one of the preceding claims, wherein the polycondensation product is applied as an aqueous solution with a solids content of 40 to 80% by weight. Method according to one of the preceding claims, wherein at least one silicone is also applied as a plasticizer. Method according to claim 4, wherein the at least one silicone is an aminosiloxane with primary and / or secondary amino groups. Method according to one of the preceding claims, wherein the at least one silicone is used as an aqueous emulsion Method according to one of the preceding claims, wherein the at least one silicone is first applied to the textile fabric and then the polycondensation product is applied to the textile fabric. Method according to one of the preceding claims, wherein the textile fabric is a cellulose-containing textile fabric. The method according to claim 8, wherein the cellulose-containing textile fabric contains fibers made from cotton, regenerated cellulose, hemp, flax, jute, sisal or mixtures thereof. A method according to claim 8 or 9, wherein the cellulose-containing textile fabric contains up to 50% by weight of polyester fibers. Process according to one of the preceding claims, wherein the polycondensation product is applied by autoclaving, dipping, spraying or painting processes. Flat textile structure with flame-retardant properties, obtainable according to one of Claims 1-11.