Patent Description:
Flame retardant treatment making use of such a condensate of THP+ salt and (thio)urea are well known and has been described e.g. in the European patent application <CIT>. In this treatment, the fabric to be treated is generally impregnated with the condensate of the THP+ salt and (thio)urea (optionally together with an amine as described in <CIT>, such as an aliphatic amine having <NUM> carbon atoms or more, such as n-docecylamine; n-octadecylamine, n-hexadecylamine, and/or n-eicosylamine) and, typically, the fabric is then dried and then cured with ammonia (NH3) whereby a phosphonium-based polymer is produced within the fibers of the fabric, which is mechanically fixed to the fabric. After the curing, the obtained polymer is generally oxidized in order to convert at least a part of the trivalent phosphorus (carried by the phosphonium group) into a pentavalent phosphorous (a phosphine oxide group). Examples of fabrics treated according to this process and textile articles and garments made thereof are those sold under the tradename PROBAN®. Example of condensates of THP+ salt and (thio)urea useful for a flame retardant of the type described above are those available under the tradename PERFORM®, for Example PERFORM®CC or PERFORM®STI.

Due to THP+ salt, the condensate as described above tend to contain formaldehyde HCHO. In the condensate of this type that have been described and used hitherto, the free formaldehyde content is systematically of more than <NUM> %. Herein, the term "free formaldehyde content" refers to the formaldehyde content by weight on the basis of total weight of composition including the condensate (which is generally an aqueous solution).

The presence of formaldehyde in the precursor is problematic given the toxicity of HCHO. This can be an issue especially during the storage and transportation, and when handling and using the precursor.

One aim of the instant invention is to provide a flame-retarding precursor having a reduced content of formaldehyde, that renders it more suitable for storage, transportation and handling. Especially, the invention aims at providing a precursor in line with the regulation regarding formaldehyde content.

To this end, the instant invention provides a precursor with a low formaldehyde content, that can be obtained by making use of a specific THP+ salt, namely THP sulfate.

In the scope of the instant invention, the inventors have now surprisingly found that it is possible to produce a condensate of THP+ salt and (thio)urea having a formaldehyde content of less than <NUM>,<NUM> % by making use of THP+ sulfate (herein referred as "THPS") instead of the THP+ chloride (noted "THPC" herein).

This result obtained with THPS is especially unexpected in view of the HCHO contents usually observed when using THPC. Usually, manufacturing a condensate of THP+ salt and (thio)urea needs an elevation of the pH of the THP+ salt (the condensate is formed at a pH of about <NUM> when the salt has a natural pH which is lower). The pH elevation is obtained by a caustic treatment, namely an addition of a strong base such as KOH or NaOH, that tend to react with the THP+ cation and form formaldehyde. And it is well known that it is difficult to manage the formaldehyde formation during the caustic treatment. The inventors have now found that the use of THPS makes it possible to have a control sufficient for limiting the formation of formaldehyde at a content that is kept under <NUM>,<NUM> % or even well lower.

In addition, the inventors have now found that the condensates having this reduced formaldehyde content (especially those obtained according to the process of the attached examples) display a significant reduced odour during application to the textile compared with condensates described in the prior art.

According to a first aspect, the instant invention relate to the compositions obtainable by making use of the THPS. More precisely, one subject-matter of the instant invention is a composition comprising a product (herein referred as "condensate") obtained by reaction of the following compounds:.

According to another aspect, another subject-matter of the instant invention is a process for preparing a composition as defined above, comprising a reaction of the aforementioned compounds (a) ; (b) ; and optionally (c), namely THPS ; (thio)urea ; and optionally an aliphatic hydroxyl-reactive compound such as an amine, in conditions leading to a free formaldehyde content of less than <NUM>,<NUM> % by weight, based on the total weight of the composition. The process comprises: allowing compounds (a) and (b) to react at a temperature of less than <NUM>; or, when compound (c) is reacted, allowing the product obtained by the reaction of compounds (a) and (c) to react with compound (b) at a temperature of less than <NUM>.

The tetrakis (hydroxyorgano) phosphonium sulfate (THPS) used in the scope of the instant invention is preferably a tetrakis (hydroxyalkyl) phoshonium sulfate. More preferably, it is a tetrakis (hydroxymethyl) phoshonium sulfate.

Different features and specific embodiments of the invention are described in more details herein-after.

According to a first variant, the composition of the invention contains, as the precursor, a product obtained by reaction of:.

without any additional aliphatic hydroxyl-reactive compound such as an amine.

Preferably, in that case, the molar ratio (a)/(b) in the condensate present in a composition of the invention (ratio of the quantity of THP+ cation to the quantity of urea) is in the range of <NUM>:<NUM> to <NUM>:<NUM> , for example in the range of <NUM>:<NUM> to <NUM>:<NUM>.

Alternatively, according to a second variant, the composition of the invention contains, as the precursor, a product obtained by reaction of:.

According to this second variant, the aliphatic hydroxyl-reactive compound is preferably a compound comprising an aliphatic chain, typically an alkyl group, having at least <NUM> carbon atoms, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> carbon atoms.

Besides, the aliphatic hydroxyl-reactive compound (c) is preferably selected from the group consisting of :.

According to a preferred embodiment, the aliphatic hydroxyl-reactive compound (c) is an amine, preferably a primary amine, comprising an alkyl group, having at least <NUM> carbon atoms, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> carbon atoms. An especially preferred aliphatic hydroxyl-reactive compound (c) is a primary alkylamine wherein the alkyl chain comprises <NUM>, <NUM> or <NUM> carbon atoms. The n-dodecylamine, n-tridecylamine and n-tetradecylamine are for example suitable amines.

Whatever the exact nature of the compound (c), it is preferred that, in the condensate present in a composition according to the second variant, the molar ratio (a)/(b+c) (ratio of the quantity of compound (a) in mole, to the sum of the quantities of compounds (b) and (c) in mole) is in the range of <NUM>:<NUM> to <NUM>:<NUM> , preferably in the range of <NUM>:<NUM> to <NUM>:<NUM> , for example in the range of <NUM>:<NUM> to <NUM>:<NUM>.

A composition according to the invention generally comprises the product resulting of the reaction of compounds (a) and (b) or the product resulting of the reaction of compounds (a), (b) and (c) dissolved in water. Alternatively, the composition of the invention may comprise additional products, provided that they do not interfere with the reaction of the precursor during the ammonia curing, for example a water soluble solvent.

The preparation of a composition of the invention makes use of a reaction of compound (a), namely THPS, with at least compound (b), this reaction being typically carried out by heating the mixture. The inventors have found that, in order to decrease the HCOH content in the compositions of the invention, it is preferable that the reaction of compounds (a) and (b) takes place at a temperature lower than the temperatures commonly used in the prior art (especially lower than the reflux conditions taught in <CIT>). Accordingly, according to the present disclosure, the reaction of compounds (a) and (b) takes place at a temperature of less than <NUM>, more preferably at a temperature of less than <NUM> (for example between <NUM> and <NUM>, e. g between <NUM> and <NUM>).

Preferably, before reacting compound (a), the process includes a step of adjusting the pH of compound (a), advantageously in order to obtain compound (a) in water at a pH of between <NUM> and <NUM>, the value <NUM> being preferably excluded (in other words, a pH of less than <NUM> - for example of less than <NUM> or even of less than <NUM> - is preferred). Advantageously, the step of adjusting the pH of compound (a) allows to obtain compound (a) in water at a pH of between <NUM> and <NUM>, more preferably in the range of <NUM>. This step of adjusting the pH generally includes the addition of a base, e.g. a strong base such as NaOH or KOH, to the compound (a) in water, in order to have the compound (a) at a pH, since typically, the pH of a THPS after its preparation is of about <NUM>. The inventors have now unexpectedly found that this step leads to a well lower formation of formaldehyde than in the case of THPC, which allow to obtain a final condensate with a reduced content of formaldehyde, provided that the THPS initially contains a sufficiently low content of formaldehyde. Preferably, the compound (a) used in the process of the invention contains less than <NUM> %, preferably less than <NUM>% of free formaldehyde before the step of adjusting pH. After the reaction of compound (a) with compound (b) and optionally (c), the content of free formaldehyde is generally not higher than, and most often lower than the content of free formaldehyde in the initial compound (a). The process may also comprise a step of adjusting the pH, that however does not lead, if any, to a substantial formation of formaldehyde.

For preparing a composition according to the first variant (reaction of compound (a) and (b) without any compound (c)), the compound (b) is typically added to the compound (a) preliminarily placed at a pH of between <NUM> and <NUM>, and more preferably in the aforementioned pH conditions where the value of <NUM> is excluded, and then the mixture is heated (below <NUM>, and more preferably below <NUM>) and compounds (a) and (b) are allowed to react. The pH is optionally adjusted after the reaction.

Hence, typically, the process preparing a composition according to the first variant comprises the following successive steps:.

For preparing a composition according to the second variant (reaction of compound (a) (b) and (c)), compound (a) is preferably reacted first with compound (c) (preferably without any (b)) and then only the product obtained by the reaction of compounds (a) and (c) is reacted with compound (b). The inventors have found that this order of the steps induces a reduction of the formation of formaldehyde.

Before the reaction with compounds (c) and (b) (in that order or alternatively (b) and then (c) even if not preferred), compound (a) is preferably preliminarily placed at a pH of between <NUM> and <NUM>, more preferably between <NUM> and <NUM>.

Besides, for preparing a composition according to the second variant (global reaction of compounds (a); (b); and (c)), the reaction of compound (b) with compound (a), or with the product obtained by the reaction of compounds (a) and (c), is carried out at a temperature of less than <NUM>, more preferably at a temperature of less than <NUM> (for example between <NUM> and <NUM>, e. g between <NUM> and <NUM>).

Typically, the process for preparing a composition according to the second variant comprises the following successive steps:.

The invention will now be further illustrated by the following illustrative examples.

A THPS-urea condensate according to the first variant of the invention (phosphonium : urea ratio of <NUM> : <NUM> ) has been prepared as follows:
<NUM> tetrakis(hydroxymethyl)phosphonium sulfate solution (<NUM> %w/w THPS, <NUM> moles) was treated with <NUM> of <NUM> %w/w sodium hydroxide solution to give a mixture with a pH of <NUM>. The mixture was heated in an oil-jacketed reactor to <NUM> and <NUM> urea (<NUM> moles) added in three portions over <NUM> minutes.

The reaction mixture was then heated to <NUM>-<NUM>, held at that temperature for <NUM> hours to complete the reaction, and then cooled. The pH of the cooled product was <NUM> and further additions of <NUM> <NUM> %w/w sodium hydroxide solution and <NUM> water were made as final adjustments.

The final product was analysed as follows.

Measurement of free formaldehyde in the THPS starting material and the final reaction product gave the following results.

The THPS-urea condensate as obtained in this example displays significantly reduced odour during application to textile.

In order to illustrate the effect of the temperature of the reaction between compounds (a) and (b) in the instant invention, the above example has been reproduced, with the same conditions, except that the reaction mixture was then heated to <NUM> instead of <NUM>-<NUM>, and held at <NUM>-<NUM> for <NUM>. <NUM> hours to complete the reaction. In these conditions, a final content of HCHO greater than <NUM> % was obtained in the THPS-urea condensate (more precisely : <NUM>%w/w HCHO even when starting from a THPS having an initial content of <NUM> %w/w HCHO).

For seek of comparison, a THPC-urea (with the same phosphonium:urea ratio of <NUM>:<NUM> as in Example <NUM> B) has been prepared as follows:
<NUM> tetrakis(hydroxymethyl)phosphonium chloride (<NUM> %w/w THPC, <NUM> moles) was treated with <NUM> <NUM> %w/w sodium hydroxide solution to give a mixture with a pH of <NUM>.

A portion of this was set aside and the remaining <NUM> (containing <NUM> THPC, <NUM> moles) was charged to an oil- jacketed reactor and heated to <NUM>-<NUM>.

<NUM> urea (<NUM>. <NUM> moles) was added in three equal portions and the reaction mixture heated to approximately <NUM> and held at that temperature for <NUM> hour. The product was then cooled and adjusted with a further <NUM> <NUM> %w/w sodium hydroxide solution and <NUM> water.

Measurement of free formaldehyde in the THPC starting material, the THPC after the initial pH adjustment and the final reaction product gave the following results.

The examples of <CIT>, that make use of THPC, have been reproduced and the free formaldehyde content has been measured. This content is systematically of more than <NUM>%.

On the contrary, a THPS-amine-urea condensate prepared in similar conditions systematically lead to a free formaldehyde of less than <NUM>,<NUM> %, especially when temperature is controlled: urea and a C18 amine as used in <CIT> were added to THPS instead of THPC (with a molar ratio THPS:urea:amine of <NUM>:<NUM>:<NUM> - addition at <NUM>), and then heated at <NUM>. The final free formaldehyde was of less than <NUM>,<NUM>%.

The content of free formaldehyde has been found even lower if the amine is added first: in the same conditions, by adding first the amine at <NUM> to the THPS, reacting at <NUM>, then cooling at <NUM> and adding the urea and heating at <NUM> for <NUM> minutes, the final free formaldehyde was of less than <NUM>,<NUM>%.

More precisely, a THPS-amine-urea condensate with a formaldehyde content of <NUM>%wt/wt was obtained as follows:
<NUM> tetrakis(hydroxymethyl)phosphonium sulfate solution (<NUM> %w/w THPS, <NUM> moles) was charged to an oil-jacketed reactor and heated to <NUM>. <NUM> tetradecylamine (<NUM> moles) was added and the mixture heated to <NUM>-<NUM> and held at that temperature for <NUM> minutes. The resulting reaction mixture was then cooled to <NUM> and <NUM> urea (<NUM>. <NUM> moles) was added in three portions over <NUM> minutes. The reaction mixture was re-heated to <NUM>-<NUM> and held at that temperature for <NUM>. <NUM> hours. After cooling an addition of <NUM> water was made as a final adjustment.

The THPS-amine-urea condensates as obtained in this example futhermore display significantly reduced odour during application to textile.

The above example has been reproduced by reacting the urea at a higher temperature (more than <NUM> instead of less than <NUM>), which leads to a HCOH content of <NUM>%:
<NUM> tetrakis(hydroxymethyl)phosphonium sulfate solution (<NUM>%w/w, <NUM> moles) was treated with <NUM> <NUM>%w/w sodium hydroxide solution to give a mixture with a pH of <NUM>. The mixture was heated to <NUM> in an oil- jacketed reactor and <NUM> urea (<NUM>. <NUM> moles) was added in three portions over about <NUM> minutes, followed by <NUM> tetradecylamine (<NUM> moles). The mixture was heated to <NUM> and maintained at <NUM>-<NUM> for <NUM> hours. After cooling, the final solution strength was adjusted by the addition of <NUM> water.

Claim 1:
A composition comprising a product obtained by reaction of the following compounds:
(a) a tetrakis (hydroxyorgano) phosphonium sulfate;
(b) urea or thiourea;
(c) optionally an aliphatic hydroxyl-reactive compound;
wherein the reaction comprises allowing compounds (a) and (b) to react at a temperature of less than <NUM>, or, when the reaction comprises compound (c), allowing the product obtained by the reaction of compounds (a) and (c) to react with compound (b) at a temperature of less than <NUM>; and
wherein the composition has a free formaldehyde content of less than <NUM>% by weight, based on the total weight of the composition.