GB2375547A

GB2375547A - Waterproofing

Info

Publication number: GB2375547A
Application number: GB0111958A
Authority: GB
Inventors: Gareth Rhys Collins; Christopher Raymond Jones
Original assignee: Rhodia Consumer Specialties Ltd
Current assignee: Solvay Solutions UK Ltd
Priority date: 2001-05-16
Filing date: 2001-05-16
Publication date: 2002-11-20
Also published as: GB0111958D0

Abstract

A method of waterproofing a substrate such as wool or leather, the method comprising the application, to the substrate, of a crosslinking agent and a waterproofing agent. The crosslinking agent may be tris(hydroxyorgano)phosphine (THP) or a tetrakis(hydroxyorgano)phosphonium salt (THP<SP>+</SP>) salt or a condensate of a THP<SP>+</SP> salt or THP with a nitrogen containing compound. The waterproofing agent is preferably an aminosilicone with primary and/or secondary amino groups.

Description

WATERPROOFING This invention relates to waterproofing and in particular to a method of waterproofing a substrate comprising wool, leather or both wool and leather.

The invention will be described herein with particular reference to the waterproofing of leather, but it is not to be construed as being limited thereto.

It is known to enhance the waterproof quality of finished leather goods by coating with a polish, a wax or the like. However, the protection afforded by these treatments is not permanent.

Previous attempts have been made to waterproof leather goods permanently using waterproofing agents. Such attempts have frequently been unsuccessful, inter alia for the following reasons.

Waterproofing agents comprise hydrophilic and hydrophobic components.

At high pH the hydrophobic components are emulsified in water by the hydrophilic components, so that an oil-in-water emulsion is obtained.

As the pH is lowered to less than 6.0, the emulsion inverts such that the water is dissolved in the oil; in effect, a water-in-oil emulsion is formed.

If the pH is decreased further to below 4 the emulsion is totally deactivated. The hydrophobic groups are then capable of waterproofing leather. Phosphates used as hydrophilic components are able to form water insoluble components with Cr3+. The acidification to below pH 4

gives an insoluble oil phase and in the water phase the hydrophilic components are"capped"off, making them insoluble.

This acidification enhances the waterproofing capacity of a substrate in a float.

A"mineral" (e. g. Cr3+) must be present in the waterproofing stage to give the capping effect, which is essential if the required level of waterproofing is to be obtained.

The presence of"minerals"at this stage is undesirable, as the"mineral" has to be disposed of and is often harmful to the environment.

It is an aim of the present invention to ameliorate the above problems.

Thus, the present invention provides a method of waterproofing a substrate, the method comprising the application, to the substrate, of a crosslinking agent and a waterproofing agent.

The substrate may, for example, comprise wool. Alternatively, the substrate may comprise a tanned or pre-tanned leather. Again, the substrate may comprise both wool and leather.

The crosslinking agent and the waterproofing agent may be applied separately or substantially simultaneously to the substrate.

Alternatively, the crosslinking agent and the waterproofing agent may be pre-reacted prior to being applied to the substrate.

In one preferred embodiment of the present invention, the crosslinking agent may be tris (hydroxyorgano) phosphine (THP) or a tetrakis (hydroxyorgano) phosphonium salt (THP+ salt) or a condensate of THP or a THP+ salt with a nitrogen-containing compound.

In a further preferred embodiment of the present invention, the crosslinking agent may be an aldehyde (e. g. formaldehyde, glutaraldehyde or a chemically-modified glutaraldehyde), an oxazolidine or a non-mineral tannage.

The waterproofing agent is preferably a silicone. The silicone is preferably an aminosilicone, for example an aminosilicone of the type available under the registered trade mark Rhodorsilo. The aminosilicone preferably comprises primary and/or secondary amino groups.

The chemical nature of Rhodorsil aminosilicone compounds is shown below. Five Rhodorsil compounds are shown, as well as another compound, Hydrosoft, all of which may be used as waterproofing agents in the present invention. Rhodorsil products are of the general formula :

Wherein:

Product A B m n H 21637 Rhodorsil# -O-CH3 -(CH2)3-NH(CH2)2-NH2 135 1.5 H 21642 Rhodorsil# -O-CH3 -(CH2)3-NH(CH2)2-NH2 270 1.5 H 21643 Rhodorsil# -O-C2H5 -(CH2)3-NH2 135 1.5 H 21645 Rhodorsil# -CH3 HALS 700 10 H 21650 Rhodorsit-CHHALS150020 Hydrosoft Rhodorsil"'-CH3 HALS 100 2 The chemical nature of HALS can be represented by the following formula :

The THP condensate is preferably a condensate of a THP+ salt and urea or a THP+ salt with an alkylamine, e. g. a Ci-zo alkylamine.

Alternatively, the THP+ salt is condensed with thiourea, guanidine, ammonia, dicyandiamide, melamine or with a mixture of two or more comonomers.

It will be appreciated that in the method of the present invention, further adjuvants known in the art may optionally be added at an appropriate stage. These adjuvants include, buffers, catalysts, syntans, surfactants, fat liquors, biocides, water dispersants, antifoams, solvents, scale inhibitors, corrosion inhibitors, chelating agents, fragrances, oxygen scavengers and/or flocculants.

The substrate (when comprising leather) may be tanned or pretanned by the application of the crosslinking agent as a first tanning step, optionally together with a syntan.

Alternatively the substrate (when comprising leather) may be tanned or pretanned by the application of aldehydes, e. g. glutaraldehyd or glyoxal, with oxazolidines or with a non mineral tannage.

Preferably, the crosslinking agent is applied (when the substrate comprises leather) to delimed and acidified skins, prior to aqueous degreasing. For example, the initial pH is below 5 e. g. below 4. It is preferred that the pH be raised to or maintained above 5 and preferably maintained above 6 for the main duration of the tanning process.

The treated leather substrate is then agitated in a tanning liquor, for a time between 1 to 24 hours, to raise the shrink temperature above 75 C.

A preferred embodiment of the invention will be described, merely by way of example, as follows: In the following example, ABRITEZ AD75M is an aqueous solution of tetrakis (hydroxymethyl) phosphonium sulphate (THPS) containing 75% a. i. THPS, and ALBRITE CC is an aqueous solution of a 2: 1 THPC/Urea condensate. RHODORSILO H21645 is alpha, omegadimethyl polydimethyl, methyl [3- (2,2, 6, 6,-tetramethylpiperidin-4 yloxy) propyl siloxane.

Pretanning of a leather substrate Bovine skin approximately 2 to 2.2mm thick was pickled through the cross section of the skin at pH 4 in a 100% float with 0.6% of 85% a. i. formic acid with a float Baume of 6 (due to 6% salt addition). 2% ABRITES AD75M was then added to the float and the skins were rotated in the float for 180 minutes to allow the ABRITE ADAM to penetrate through the skin at a low pH.

The float was then basified to pH 6.0 over a further 210 minutes by addition of 0. 5% sodium bicarbonate every 30 minutes.

The resulting substrate demonstrated tanning throughout its cross section (as shown by a selenium indicator response and confirmed by checking the shrinkage temperature of the substrate).

The leather substrate was then sammed and split to a thickness of between 1 to 1.2 millimetres (mm) before waterproofing was commenced.

Waterproofing the leather substrate. a 1. 0% of Rhodorsile H21645 (based on the wet white weight) was added to a 150% float, with the leather substrate in it, at a pH of between 5.5 to 6.0. This was then rotated at room temperature for 120 minutes.

6. 4% formic acid was then added to the float to lower the pH to below 3 and left for a further 120 minutes. p The procedure of a was repeated but with the subsequent addition of ABRITEZ CC 10 minutes after the addition of Rhodorsile H21645 and this was subsequently rotated for 110 minutes instead of 120 minutes.

y The procedure of ss was repeated but rotation was carried out for 230 minutes and no formic acid repickle was applied.

8 The procedure of a was repeated but 30 minutes after the formic acid repickle was started 1. 0% ABRITEZ CC was added to the float and rotated for a further 90 minutes.

Following these treatments each float was drained and two 300% water washes were applied to the skins for 20 minutes each.

The float was then drained and the leather substrates removed from their respective tanning vessels. Each leather substrate was left to dry for 48 hours in the open air.

Following this the samples were subjected to the 3M water repellence test method (water/alcohol drop test).

In this procedure drops of a test liquid comprising specified proportions of water and isopropyl alcohol by volume are placed on a surface of the substrate and observed for wetting. If the substrate does not absorb the liquid, it has adequate water repellence to pass the test. The correlation of the test liquid and the water repellence of the sample is shown in Table A below.

Table A

% composition of the test liquid Water repellence Rating Water W 90/10 water/isopropy1 alcohol 1 80/20 2 70/30 3 60/40 4 50/50 5 40/60 6 30/70 7 20/80 8 10/90 9 100 isopropyl alcohol 10 One sample from each waterproofing procedure was used. The sample was approximately 20cm x 20 cm.

The procedure was carried out as follows : 1. The sample was placed on a flat horizontal surface.

2. Using a pipette, three small drops of liquid were gently placed on each of two or three different areas of the sample.

3. The drops were allowed to stand undisturbed for 10 seconds.

Evaluation and Rating If, after 10 seconds, two of the three spherical to hemispherical drops were still visible on the substrate surface, the substrate passed the test.

Substrates were rated as a pass or fail on the appropriate liquid. The numerical rating is the rating of the highest numbered test liquid (see

Table A) which remained visible as a spherical or hemispherical droplet. The correlation between sample number and sample rating is shown in Table B below.

Table B

Sample No Sample rating a 6 P 9 7 9 Ò Control The addition of a THP condensate after the leather substrate has been treated with an aminosilicone gives a high, permanent, water repellence rating (samples 2 and 3). A rating of 9 indicates the leather has a substantial resistance to both oil and water damage. The control used is a leather substrate tanned with ABRITEZ AD75, without any treatment with aminosilicones or aminosilicones in conjunction with THP or a THP+ salt or with a condensate of THP or a THP+ salt with a nitrogen containing compound.

Claims

CLAIMS 1. A method of waterproofing a substrate, the method comprising the application, to the substrate, of a crosslinking agent and a waterproofing agent.
2. A method as claimed in Claim 1, in which the substrate comprises wool.
3. A method as claimed in Claim 1, in which the substrate comprises a tanned or pretanned leather.
4. A method as claimed in any one of the preceding claims, in which the substrate comprises both wool and leather.
5. A method as claimed in any one of the preceding claims, in which the crosslinking agent and the waterproofing agent are applied separately to the substrate.
6. A method as claimed in any one of Claims 1 to 4, in which the crosslinking agent and the waterproofing agent are applied substantially simultaneously to the substrate.
7. A method as claimed in Claim 6, in which the crosslinking agent and the waterproofing agent are pre-reacted prior to being applied to the substrate.
8. A method as claimed in any one of Claims 1 to 7, in which the crosslinking agent is a tris (hydroxyorgano) phosphine (THP), a tetrakis

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(hydroxyorgano) phosphonium salt (THP+ salt) or a condensate of THP or a THP+ salt with a nitrogen-containing compound.
9. A method as claimed in Claim 8, in which the THP condensate is a condensate of a THP+ salt and urea.
10. A method as claimed in Claim 8, in which the THP condensate is a condensate of a THP+ salt with an alkylamine.
11. A method as claimed in Claim 10, in which the alkylamine is a C, to C20 alkylamine.
12. A method as claimed in Claim 8, in which the THP condensate is a condensate of a THP+ salt with thiourea, guanidine, ammonia, dicyandiamide or melamine or with a mixture of two or more comonomers.
13. A method as claimed in any one of Claims 1 to 7, in which the crosslinking agent is a aldehyde, an oxazolidine or a non mineral tannage.
14. A method as claimed in Claim 13, in which the crosslinking agent is formaldehyde, glutaraldehyd or a chemically modified glutaraldehyd.
15. A method as claimed in any preceding claim, in which the waterproofing agent is a silicone.
16. A method as claimed in Claim 15, in which the silicone is an aminosilicone.

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17. A method as claimed in Claim 16, in which the aminosilicone comprises primary and/or secondary amino groups.
18. A method as claimed in any one of the preceding claims, in which adjuvants are added before, during or after application of the waterproofing agent and/or the crosslinking agent to the leather substrate.
19. A method as claimed in Claim 18, in which the adjuvants are selected from any one or more of buffers, catalysts, syntans, surfactants, fat liquors, biocides, water dispersants, antifoams, solvents, scale inhibitors, chelating agents, fragrances, oxygen scavengers and flocculant.
20. A method as claimed in any one of Claims 3 to 19, in which the leather substrate is tanned or pretanned by the application thereto of the crosslinking agent as a first tanning step, optionally together with a syntan.
21. A method as claimed in any one of Claims 3 to 19, in which the leather substrate is tanned or pretanned by the application thereto of an aldehyde, an oxazolidine or a non-mineral tannage.
22. A method as claimed in Claim 21, in which the aldehyde is glutaraldehyd or glyoxal.
23. A method as claimed in any one of Claims 3 to 22, in which the crosslinking agent is applied to delimed and acidified skins prior to aqueous degreasing.

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24. A method of waterproofing a substrate, substantially as hereinbefore described with reference to Example 3.