Synthetic fatliquor for low fogging upholstery leather

Description

[0001] The present invention is directed to synthetic fatliquors for leather treatment, having both reduced fogging characteristics and excellent light and heat fastness. Said fatliquors are particularly suitable for use in the treatment of vehicle upholstery leather.

[0002] It has been found that mono- and di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7 when used as fatliquoring agents, impart to the leather low fogging properties.

[0003] This characteristic was completely unexpected because similar products, having a number of moles of oxide lower than 7, do not show the same low fogging behavior.

[0004] The term "fogging" as used herein means the condensation on the glass windows, and particularly on the windshield, of substances released by the interior outfit of the vehicle; fogging produces misting and hinders an unimpeded vision of the driver, especially in the darkness and when the driver is faced with lights of oncoming traffic.

[0005] Moreover, the substances condensed on the glass windows bind the dust and dirt particles brought through the fan into the vehicle interior, causing a further visibility impairment.

[0006] It is therefore highly desirable that vehicle upholstery leather exhibits low fogging characteristics.

[0007] The physical and aesthetic requirements for a particular piece of leather are highly dependent on the designated end use of the leather. For example, in one application, a piece of leather may be treated primarily to provide it with strength, its aesthetic qualities being of much less importance for its intended use.

[0008] In upholstery applications, both softness and strength are required. In vehicle upholstery, as for example in automobiles and aircraft, the treated leather should also not contribute to fogging.

[0009] Treating hides and skins to form leather involves a number of interdependent chemical and mechanical operations and each of these operations has an effect on the final properties of the treated leather product, see Leather Facts, New England Tanners (1972). One important chemical operation in the treatment of leather is fatliquoring.

[0010] Fatliquoring is used to impart the desired strength and temper properties to tanned leather.

[0011] Faliquors lubricate the leather fibers so that after the leather is dried its fibers are capable of sliding over one another.

[0012] In addition to regulating the pliability of the leather, faliquoring contributes greatly to the tensile and tear strength of the leather.

[0013] Fatliquoring also affects the tightness of the break or crease pattern formed when the grain surface is bent inward, the objective being to produce a leather which leaves no or few fine wrinkles when bent.

[0014] The basic ingredients used in conventional fatliquoring operations are water insoluble oils and fatty substances such as raw oils and sulfated and sulfited oils.

[0015] Typically the weight percent of fatliquor oil on weight of leather ranges from 3 to 15 percent.

[0016] The manner in which the oil is distributed throughout the leather affects the character of the leather and subsequent finishing operations. In order to obtain an uniform oil coating over a large surface of leather fibers it is typically necessary to dilute the oil with an organic solvent or preferably to disperse the oil in an aqueous system using emulsifiers. For example, see Leather Technician's Handbook, J.H. Sharphouse, Leather Producers' Association (1971) chapters 21 and 24.

[0017] Synthetic fatliquors are also known, such as esters of fatty acids having high molecular weight with alcohols or polyalcohols and the mono- and di-sulfosuccinates of fatty alcohols described in DE 1669347.

[0018] Mono- or di-esters of sulfosuccinic acid with ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide ranging between 1 and 6 are reported in the patent literature, together with their use as fatliquoring agents, but in combination with other ingredients (see US 4744794, US 4655187, US 4729767).

[0019] In Das Leder, 1988, Issue 9, Fat Liquors and "Fogging"- the Influence of Various Raw Materials and their Processing Methods, by M. Kaussen, pages 161-165 (translation) it is stated that fogging results from all volatile substances in the interior equipment including the substances from fabrics, plastics and leather. Analyses of fogging derived from leather show that a number of chemicals used in conventional leather treatment operations contribute to fogging such as, for example, residual natural fats in wet blues, phenolic fungicides, dyestuffs, phthalates and mineral oil additives used as anti-dust agents, solvents, emulsifiers and plasticizers used in finishes. However, the most important of all the factors contributing to the fogging coming from the leather has been found to be due to the fats which directly result from the fatliquoring leather treatment step. This publication stresses the importance of a degreasing step to reduce leather fogging and generally suggests that fatliquors used in car upholstery leather manufacture should, if possible, contain no solvents or preferably be substances which are not very volatile. This publication concludes, based on specific fogging measurements, that fatliquors based on paraffin sulfonates, chloroparaffin sulfonates, fat sulfites and fish oil sulfites show good fogging results.

[0020] "Fogging Characteristics of FatLiquors and CarSeat Leathers: Part 1 Preliminary Studies, Samir Das Gupta (May 11, 1989), discusses the state of the art in leather fogging testing, particularly reflectance tests and gravimetric tests. In evaluating these tests a number of conventional fatliquors were used. Attempts to correlate the extent of volatile substances in the fatliquor and the fogging behavior were not successful.

[0021] In some aspects, the conclusions of Das Gupta evaluation, particularly with respect to sulfonated fish oil and sulfonated chloroparaffins, were exactly the opposite of the one reported in the above cited Das Leder study.

[0022] One reason for this was reported to be due to the significant differences between the reflectance fogging tests and gravimetric fogging tests; the gravimetric test being considered a more rigorous test.

[0023] The fogging characteristics of leather are normally measured according to the German standard method DIN 75201 which includes both a gravimetric and a reflectance tests.

[0024] Some auto-makers have published their own fogging test procedures and have established their own fogging requirements. Some of these are reflectance tests, as for example Ford Motor Company, and some also incorporate gravimetric tests, such as Daimler-Benz.

[0025] In the present text, with the expression " low fogging leather" we mean a leather exhibiting low fogging characteristics when the fogging is measured according to DIN 75201; with the expression "low fogging fatliquor" we mean a fatliquor enabling to obtain a "low fogging leather".

[0026] According to the patent literature different technological solutions are proposed to satisfy the low fogging demand.

[0027] Low fogging fatliquoring agents are described in EP 753585 and in US 6084467.

[0028] In EP 753585 the use of a pretreated emulsified oil is suggested. Such a pretreatment consists in removing low molecular weight substances, and other components, by distillation.

[0029] US 6084467 describes a composition for the treatment of leather obtained by

A) polymerization of water soluble acrylic monomers;

B) reaction of the thus obtained polymer with a fatty amine;

C) further (optional) reaction of the residual amine with acrylic acid or with the carboxylic groups of the polymer;

D) neutralization.

[0030] According to the above cited literature, it has not been established yet a clear correlation between the chemical properties of the fatliquor and the fogging behavior of the leather and a low fogging leather is only obtainable both using fatliquors containing more than one active substances and by means of specific technological steps.

DETAILED DESCRIPTION.

[0031] It is an object of the present invention a low fogging fatliquor, capable of imparting to the leather softness and light and heat fastness, whose active part consists of one or more mono- or di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7, preferably greater than 10.

[0032] The fatliquor of the invention may be in the form of an aqueous solution or emulsion.

[0033] According to a particular aspect of the present invention, the active part of the fatliquor is in the form of an aqueous emulsion and it is present in an amount ranging from 30 to 90% by weight, preferably from 50 to 85% by weight.

[0034] The aqueous emulsions useful for the realization of the present invention optionally further contain water soluble organic solvents.

[0035] It is another object of the present invention a method for treating the leather for vehicle upholstery, characterized by applying to the leather in a fatliquoring step, an aqueous composition of one or more mono- or di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7, preferably greater than 10, the amount of the mono- or di-sulfosuccinates applied being between 5 and 25% by weight, preferably between 8 and 15 % by weight, referring to the weight of the leather at the wet-blue step, and the aqueous composition containing from 1 to 30% by weight of said mono- or di-sulfosuccinates.

[0036] According to a preferred aspect of the present invention the aqueous composition contains from 3 to 10% by weight of one or more mono- or di-sulfosuccinates of ethoxylated and/or propoxylated alcohols.

[0037] The fatliquors of the invention are easily obtainable in the form of an aqueous emulsion, by reacting maleic anhydride or maleic acid or fumaric acid with an ethoxylathed and/or propoxylated fatty alcohol, an then sulfiting the ester in water or in a hydro alcoholic mixture.

[0038] The thus obtained aqueous emulsions can be directly used as fatliquors, according to the procedures well known by people skilled in the art.

[0039] According to another advantageous aspect of the invention the aqueous emulsions are stable even without containing an emulsifying product.

[0040] Advantageously, the aqueous emulsions of the present invention contain, as fatliquoring agent, only mono or di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7.

[0041] However, said mono- or di-sulfosuccinates are compatible with other fatliquoring agents and can be used in mixture with them.

[0042] When suitably formulated, the aqueous emulsions of the present invention can be used as fatliquors also for shoes and upholstery leathers.

[0043] In the following examples the fatliquors according to the invention are evaluated comparing both the fogging characteristics and the heat and light fastness of the leather treated with them or with other commercially available fatliquors.

[0044] The fogging characteristics of the leather were measured according to the standard DIN 75201 both by the reflectance test and by the gravimetric test.

[0045] The results obtained with the gravimetric test are reported in g/50 cm²; the lower the value, the lower the fogging.

[0046] The results obtained with the reflectance test are reported in percentage; the higher the value, the lower the fogging.

[0047] The light fastness was measured according to the standard UNI 7639; the higher the value, the lower the yellowing and thus the better light fastness.

[0048] The heat fastness was measured by treating a piece of leather at 80°C, for 72 hrs at 100% humidity; the evaluation was made by comparison with the "grey scale", according to standard ISO 105-A03; the higher the values the better the heat fastness.

[0049] Three series of tests were made, (respectively reported in Examples 1 - 4,

[0050] Examples 5 - 8, Examples 9 - 12) using three chrome tanned bovine leathers, one for each series.

[0051] The procedure described in the examples is suitable, however, for other types of hides and skins, such as mineral (chrome, aluminum zirconium, titanium, magnesium) tanned animal substrates such as pigskins, sheepskins, and the like.

Example 1

[0052] The Fatliquor 1 is prepared as described below.

[0053] A reactor, provided with both heating and cooling system, suitable stirring system and thermometer, is fed with 2840.5 g of 30 moles propoxylated, 3 moles ethoxylated cetyl stearyl alcohol. At a temperature of about 100 °C, 135.6 g of maleic anhydride are added. The temperature is maintained at 100°C until the reaction mixture reaches an acidity number of 26(+/-2); then 450.2 g of hexylene glycol and 899.7 g of water are added, and the temperature is lowered to about 70 °C. 174 g of anhydrous sodium sulfite are then added in about 20 minutes, and the temperature is raised to about 90 °C. The reaction mixture is stirred at this temperature for about 3 hours and then is cooled; a hydro glycolic solution (about 4500 g) is obtained, its dry fraction, mainly constituted of the sulfosuccinic monoester of 30 moles propoxylated, 3 moles ethoxylated cetyl stearyl alcohol, being 70% by weight.

[0054] The wet blue cowhide is treated as described hereafter.

[0055] All percentage are in weight and based on the blue stock (100% means a weight equal to the weight of the stock in the drum).

[0056] The wet blue is given a thirty minute water wash, at 35 °C with 200% of water and 0.5% of Alkilarol NF (an anionic surfactant commercialized by Lamberti S.p.A.).

[0057] The drum is drained.

150% water, 1% of sodium formate, 0.2% of sodium bicarbonate are added and the mixture is then drummed (mixed) for 30 minutes at 35 °C. The pH of the bath is 4.5.

4% of Reotan PM (acrylic resin commercialized by Lamberti S.p.A.) and 0.5% of Lamtan TN Liq. (synthetic tannin commercialized by Lamberti S.p.A.) are then added and the mixture is drummed (mixed) for 30 minutes.

4% of Lamtan CRT (synthetic tannin commercialized by Lamberti S.p.A.) is then added to the drum and the mixture is drummed (mixed) for 60 minutes.

[0058] The drum is left in automatic rotation during the night.

[0059] The drum is then drained, the stock is washed and then a new bath is prepared with

200% water at 35 °C;

2% of sodium formate

2% of sodium bicarbonate.

[0060] The mixture is then drummed (mixed) for 90 minutes.

[0061] The drum is then drained.

[0062] For the fatliquoring step, 200% of water and 12% of Fatliquor 1 are added and the mixture is drummed for 60 minutes.

[0063] 1% of formic acid is then added and the mixture is drummed (mixed) for 20 minutes.

[0064] The drum is then drained.

150% of water at 35 °C and 0.5% of Alkilarol NF are then added and

the mixture is drummed (mixed) for 20 minutes.

[0065] The drum is then drained.

[0066] On the dried leather the fogging and the light and heat fastness are measured as above described.

[0067] The results are reported in Table 1.

Example 2 (comparative)

[0068] A piece of the bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by a fatliquor made of 65%wt of sulfited fish oil and 35%wt of water (Fatliquor 2).

[0069] The fogging and the light and heat fastness are measured as above described.

[0070] The results are reported in Tablel.

Example 3 (comparative)

[0071] A piece of the bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by CORIPOL SMA/3 (Fatliquor 3), a low fogging fatliquor commercialized by TFL.

[0072] The fogging and the light and heat fastness are measured as above described.

[0073] The results are reported in Table1.

Example 4 (blank)

[0074] A piece of the bovine leather is treated as described in Example 1 but omitting the fatliquoring step.

[0075] The fogging and the light and heat fastness are measured as above described.

[0076] The results are reported in Tablel.

Table 1

Example	Fatliquor	Gravimetric fogging test (g/50cm2)	Reflectance fogging test (%)	Light fastness	Heat fastness
1	1	1,5	92,0	5	4/5
2	2	2,1	78,2	2	2
3	3	1,9	90,0	3	3
4	none	2,5	90,5	4	4/5

Example 5

[0077] Fatliquor 4 is prepared as described below.

[0078] A reactor, provided with both heating and cooling system, suitable stirring system and thermometer, is fed with 2923.5 g of 15 moles propoxylated cetyl stearyl alcohol. At a temperature of about 100 °C 251.5 g of maleic anhydride are added. The temperature is maintained at 100°C until the reaction mixture reaches an acidity number of 45(+/-2), then 875 g of water are added and the temperature is lowered to about 70 °C.

[0079] 324.9 g of anhydrous sodium sulfite are then added in about 20 minutes, and the temperature is raised to about 90 °C.

[0080] The reaction mixture is stirred at this temperature for about 3 hours and then is cooled; a hydro glycolic solution (about 4375 g) is obtained, its dry fraction, mainly constituted of the sulfosuccinic monoester of 15 moles propoxylated cetyl stearyl alcohol, being 70% by weight.

[0081] A piece of the bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by Fatliquor 4.

[0082] The fogging and the light and heat fastness are measured as above described.

[0083] The results are reported in Table 2.

Example 6 (comparative)

[0084] A piece of the bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by 65%wt of sulfited fish oil and 35%wt of water (Fatliquor 5).

[0085] The fogging and the light and heat fastness are measured as above described. The results are reported in Table 2.

Example 7 (comparative)

[0086] A piece of the bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by CORIPOL SMA/3 (Fatliquor 6), a low fogging fatliquor commercialized by TFL. The fogging and the light and heat fastness are measured as above described.

[0087] The results are reported in Table 2.

Example 8 (blank)

[0088] The last piece of bovine leather is treated as described in Example 1 but omitting the fatliquoring step.

[0089] The fogging and the light and heat fastness are measured as above described.

[0090] The results are reported in Table 2.

Table 2.

Example	Fatliquor	Gravimetric fogging test (g/50cm2)	Reflectance fogging test (%)	Light fastness	Heat fastness
5	4	0,6	94,5	5	4/5
6	5	1,5	90,0	3	2
7	6	1,0	93,0	4	3
8	None	1,2	93,0	4	4/5

Example 9

[0091] A piece of bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case Fatliquor 1 is replaced by Fatliquor 4.

[0092] The fogging is measured as above described.

[0093] The results are reported in Table 3.

Example 10

[0094] A piece of bovine leather is treated as described in Example 1 (using in the fatliquoring step Fatliquor 1).

[0095] The fogging is measured as above described.

[0096] The results are reported in Table 3.

Example 11 (comparative)

[0097] A piece of bovine leather is treated as described in Example 1 except for the fatliquoring step: in this case, the Fatliquor 1 is replaced by 80%wt of the sulfosuccinic monoester of 6 moles propoxylated cetyl stearyl alcohol and 20% of water (Fatliquor 7).

[0098] The fogging is measured as above described.

[0099] The results are reported in Table 3.

Example 12 (blank).

[0100] A piece of bovine leather is treated as described in Example 1 but omitting the fatliquoring step.

[0101] The fogging is measured as above described.

[0102] The results are reported in Table 3.

Table 3

Example	Fatliquor	Gravimetric fogging test (g/50cm2)	Reflectance fogging test (%)
9	4	0,45	99,7
10	1	0,55	93,2
11	7	0,75	89,8
12	None	0,40	98,8

Claims

1. Low fogging fatliquor characterized by the fact that its active part consists of one or more mono- or di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7.

2. Low fogging fatliquor according to claim 1., wherein the number of moles of oxide is greater then 10.

3. Low fogging fatliquor according to claim 2., characterized by the fact that its active part is in the form of an aqueous emulsion and it is present in an amount ranging from 30 to 90% by weight

4. Low fogging fatliquor according to claim 3., characterized by the fact that its active part is in the form of an aqueous emulsion and it is present in an amount ranging from 50 to 85% by weight.

5. A method for treating the leather for vehicle upholstery, characterized by applying to the leather in a fatliquoring step an aqueous composition of one or more mono- or di-sulfosuccinates of ethoxylated and/or propoxylated fatty alcohols with a number of moles of oxide greater than 7, the amount of the mono- or di-sulfosuccinates applied being between 5 and 25% by weight, referring to the weight of the leather at the wet-blue step, and the aqueous composition containing from 1 to 30% by weight of said mono- or di-sulfosuccinates.

6. A method for treating the leather for vehicle upholstery according to claim 5., wherein the number of moles of oxide of the mono- or di-sulfosuccinates of ethoxylated or propoxylated fatty alcohols is greater than 10.

7. A method for treating the leather for vehicle upholstery according to claim 6., wherein the amount of the mono- or di-sulfosuccinates applied is between 8 and 15 % by weight.

8. A method for treating the leather for vehicle upholstery according to claim 6., wherein the aqueous composition contains from 3 to 10% by weight of said mono- or di-sulfosuccinates of ethoxylated or propoxylated fatty alcohols.