EP0032219A1 - Process for manufacturing artificial leather - Google Patents

Abstract

The artificial leather is produced in the form of a web whose properties regarding softness, flexibility, moisture absorbtivity, water and air permeability, etc. correspond at least to those of natural leather. The web is formed using fibres of which at least some have been rendered hydrophobic by impregnation with a water repellent.

Description

The present invention relates to a process for producing synthetic leather in the form of a nonwoven whose properties in terms of softness, flexibility, moisture absorption capacity, water and air permeability, etc. are at least equivalent to those of a natural leather.

It is already known to produce synthetic leather or other leather substitute material in the form of a fleece. In such known processes, nonwovens are made from layered synthetic fibers or threads or from endless synthetic fibers or threads (also called chemical fibers), e.g. "Needled", impregnated with latex or polyurethane products, vulcanized or coagulated, if necessary split and then coated and finished with known coating compositions, depending on the intended use. The materials produced in this way are disadvantageous in that they have low flexibility (flexibility) and inadequate drapability.

As is known, the softness and the grip of a nonwoven, such as, for example, a nonwoven that forms the basis of synthetic leather, is dependent on the number of adhesion points between the fiber surface and the binder used in each case, or on the proportionate size of the binder-free fiber surface. The smaller the number of adhesion points and the larger the binder-free fiber surface, the greater the mobility of the fibers within the fleece bandage they form when subjected to bending stress.

Furthermore, the softness and the feel of such a fleece are known to depend on the fiber titer, i.e. the fleece is the softer the greater the degree of fineness of the fibers forming the fleece.

From DE-AS 20 23 214 it is known that very fine fibers (so-called microfine fibers or microfibers) can be produced with a fiber titer of about 0.1 denier; these fibers enable the production of nonwovens or synthetic leather with excellent softness. A synthetic leather produced according to the method described in this document has such microfine fibers and also a relatively small number of adhesion points, since in the case of microfibers in the form of bundles only the capillary fibers or threads located in the peripheral or peripheral zone of the bundles are through the bandage used = or. Impregnant bound, while the capillary fibers inside the bundles slide against each other under the influence of a bending stress, i.e. can move each other.

However, this known method for producing a synthetic leather with high softness is complicated and involves considerable technical effort. This applies not only to the manufacture of the microfibers themselves, but also to the subsequent process steps of finishing or processing the felt fleece obtained in order to manufacture the desired end product, i.e. of the synthetic leather.

It has now surprisingly been found that the nonwoven properties required for producing a synthetic leather with high flexibility and favorable water absorption = and water permeability properties (or water distribution properties) within the synthetic leather, namely in particular high mobility of the fibers within the nonwoven, a comparatively small number of adhesion points Large binder-free fiber surface, can be achieved in a simple manner by using natural or synthetic fibers or a mixture thereof for the production of the nonwoven, which are at least partially hydrophilic, the fibers preferably in the form of staple fibers (layered fibers), but also if appropriate in the form of continuous fibers = or threads.

The invention consequently relates to a method for producing an artificial leather by forming a fleece from staple fibers or the like. the fibers being opened on a carding machine or a pneumatic nonwoven formation system, laid to form a nonwoven, pressed, preferably needled, optionally shrunk, impregnated with a binder, optionally split, optionally ground, roughened, brushed and optionally are coated, characterized in that fibers are used for the formation of fleece, which at least partially consist of fibers impregnated with a hydrophobizing agent.

The proportion of hydrophobized fibers in the fleece can be 5 to 100%, preferably 5 to 90% and in a particularly advantageous embodiment 30 to 70%.

Any known products with a water-repellent effect can be used as water repellents, such as oils, fats, fatty acid salts and preferably silicones or silicone-containing products. The amount of hydrophobizing agent applied depends on the type of agent and on the type of fiber to be hydrophobicized, e.g. Wool, cotton, polyamide, polyacrylonitrile, polyester, polypropylene, cellulose, etc. as well as the effect desired for the respective article.

The application amount of hydrophobizing agent is generally 0.05 to 5% by weight, preferably 0.1 to 2% by weight (based on the hydrophobized fiber material).

By using mixtures of fibers with different swelling behavior preferred according to the invention, a targeted, graded hydrophobization of the fibers can be achieved.

The method according to the invention can e.g. are carried out in such a way that a non-needled or preferably needled non-woven fabric made of the fibers exemplified above or their mixtures with a uniform, uniform fiber distribution over the entire non-woven cross section before the impregnation known per se (for example with a latex or a polyurethane) with one of the hydrophobicizing agents mentioned, is preferably made hydrophobic by means of an immersion or spray treatment. However, previously hydrophobicized fibers or mixtures of hydrophobicized and non-hydrophobicized fibers can also be used to form the nonwoven.

According to the invention, a fleece constructed in a sandwich construction is very particularly preferably used as the base fleece for the synthetic leather. This fleece can preferably be needled but not needled. In this sandwich structure, the individual layers can contain fibers of the same type, but they can also consist of different fibers. The use of fibers with different swelling behavior is particularly preferred. In this way, the desired fleece or synthetic leather properties can be achieved. eg by suitable choice of the type and amount of fibers or Adjust fiber mixtures in the individual layers and by a suitable choice of the arrangement of the fiber layers to one another and by a suitable choice of the type and amount of the hydrophobizing agent.

For example, a two-size, needled nonwoven is produced, in which one layer consists of polyamide and the other layer consists of a mixture of polyamide and viscose fibers with about 80% viscose, and this nonwoven contains a silicone emulsion containing 1 percent Si-H groups impregnated after the immersion process, then dried and briefly heated to 140 ° C. for crosslinking, then the water-repellent effect of the polyamide / viscose layer is greater than that of the polyamide layer. In the subsequent impregnation with a known latex, the affinity of the polyamide layer to the latex is greater than that of the viscous layer, but less than in the case of a polyamide fiber layer not impregnated with silicone products. The base fleece obtained in this way is overall softer than a base fleece without silicone impregnation and also has more favorable moisture permeability properties in the synthetic leather if the polyamide fiber side is coated and the viscous layer forms the leather inside.

The water treatment of the viscose remains largely unaffected by the silicone treatment.

If, for example, a 3-layer fleece is made hydrophobic in such a way that the most hydrophilic layer forms the middle fleece layer, then after the impregnation with latex a base fleece is obtained, the density of which decreases uniformly from the center to both sides. The base fleece and a synthetic leather made from it by coating is extremely soft and has e.g. pleasant wearing properties are used as upper leather. If you increase the mass of the individual layers, in particular that of the middle layer described, you can obtain two basic nonwovens by splitting this middle layer, as described in the 2-layer nonwoven structure.

A special embodiment of the method according to the invention consists in using a nonwoven made of two layers as the base nonwoven, in which only one layer contains fibers, at least some of which are hydrophobized and that the needling of the two layers takes place in such a way that at least during the last needle pass the needles only enter from the side that contains the hydrophobized fibers and that the penetration depth is such it is chosen that fiber tufts are pushed through on the hydrophobing agent-free layer facing away from the puncture side and provide a velor (velvet) after roughening and brushing.

According to the method according to the invention, non-woven synthetic leather with a particularly soft and pleasant grip can be obtained if the impregnation with latex binders takes place in the manner described in DE-OS 2502 654, DE-OS 25 02 655 or DE-OS 26 01 781.

example 1

A random fiber fleece consisting of 60% hydrophobic polyamide fiber (approx. 40 mm stack length, 1.6 dtex) and 40% polyester fiber (approx. 40 mm stack length 1.6 dtex) is impregnated with an excess of a latex mixture of the composition given below, so that pro 100 g fiber material 100 g solid material can be taken from the latex mixture. The impregnated fleece is then quickly heated to 50 ° C, causing the latex mixture to gel. Then it is vulcanized with steam at 150 ° C for 30 minutes and then the fleece is dried in hot air. A microporous synthetic leather base material is obtained by splitting the fleece.

• 210,0 Gew-Teile eines 47 %-igen Latex eines Copolymerisates
  • aus 60,0 Gew.-% Butadien
  • 36,0 Gew.-% Acrylnitril
  • und 4,0 Gew.-% Methacrylsäure (= 100 Gew.-Teile Trockensubstanz).
• 15 Gew.-Teile Poly-dimethylsiloxan, Emulsion 33 %-ig
• 1,0 Gew.-Teile eines Polyäthersiloxans
• 2,0 Gew.-Teile Benzylphenylphenol
• 75,0 Gew.-Teile Wasser
• 41,0 Gew.-Teile einer Vulkanisationspaste aus
  • 2 Gew.-Teilen Kolloidschwefel
  • 5 Gew.-Teilen Zinkoxyd
  • 1 Gew.-Teil Zinkdiäthyldithiocarbamat
  • 5 Gew.-Teilen Titandioxyd
  • 1 Gew.-Teil diisopropyldithiocarbaminsaures Natrium
  • und 27 Gew.-Teile einer 5 %igen Lösung eines Kondensationsproduktes aus Naphthalinsulfonsäure mit Formaldehyd.

Der Koagulationspunkt dieser Latexmischung ist ca. 40°C.The latex mix used has the following composition:

• 210.0 parts by weight of a 47% latex of a copolymer
  • from 60.0% by weight of butadiene
  • 36.0% by weight acrylonitrile
  • and 4.0% by weight of methacrylic acid (= 100 parts by weight of dry substance).
• 15 parts by weight of poly-dimethylsiloxane, emulsion 33%
• 1.0 part by weight of a polyether siloxane
• 2.0 parts by weight of benzylphenylphenol
• 75.0 parts by weight of water
• 41.0 parts by weight of a vulcanization paste
  • 2 parts by weight of colloidal sulfur
  • 5 parts by weight of zinc oxide
  • 1 part by weight of zinc diethyldithiocarbamate
  • 5 parts by weight of titanium dioxide
  • 1 part by weight of diisopropyldithiocarbamic acid sodium
  • and 27 parts by weight of a 5% solution of a condensation product of naphthalenesulfonic acid with formaldehyde.

The coagulation point of this latex mixture is approx. 40 ° C.

example

A fiber mixture consisting of 70% siliconized polyamide fibers 1.6 dtex / 40 mm and 30% polyester high shrink fibers 1.3 dtex / 60 mm is crumpled, cross-laid and needled with a 38 mm needle using a known method.

The fleece weight is approx. 350 g / m ² ; the puncture density 750 / cm ² . The fleece is then shrunk at about 70 ° C. The shrunk nonwoven, the weight of which is approx. 450 g / m ² , is impregnated with a polyurethane solution (approx. 50% solids coating) by the coagulation process, coagulated, washed and dried.

• 9 kg Dispersion eines kationischen Polyurethans auf der Basis eines Polyesters aus Phthalsäure, Adipinsäure und Athylenglykol (Molverhältnis 1:1:2,2), Toluylendiisocyanat, N-Methyl-diäthanolamin und 1,4-Dichlorbuten in einem Wasser/Dimethylformamid-Gemisch 25 %ig in DMF ;
• 3 kg eines Polyurethans aus einem Gemisch von Hexandiolpolycarbonatester und Adipinsäurebutandiol- 1,4-ester, 4,4'-Diphenylmethan-diisocyanat und 1,4 Butandiol (25 %ig in DMF)
• 0,5 kg eines Polyurethans aus Adipinsäurebutandiol-äthylenglykol-Mischestern, 4-4-Diphenylmethan-diisocyanat und 1,4-Butandiol (25 %ig in DMF).
• 0,05 kg Magnesiumchlorid 20 %ig
• 0,01 kg eines handelsüblichen Weissgerbstoffes.

The polyurethane solution has the following known (DE-AS 12 70 276, DE-AS 16 94 171) composition:

• 9 kg dispersion of a cationic polyurethane based on a polyester of phthalic acid, adipic acid and ethylene glycol (molar ratio 1: 1: 2.2), tolylene diisocyanate, N-methyl-diethanolamine and 1,4-dichlorobutene in a water / dimethylformamide mixture 25% ig in DMF;
• 3 kg of a polyurethane from a mixture of hexanediol polycarbonate ester and adipic acid butanediol 1,4-ester, 4,4'-diphenylmethane diisocyanate and 1,4 butanediol (25% in DMF)
• 0.5 kg of a polyurethane composed of adipic acid-butanediol / ethylene glycol mixed esters, 4-4-diphenylmethane diisocyanate and 1,4-butanediol (25% in DMF).
• 0.05 kg magnesium chloride 20%
• 0.01 kg of a commercially available white tanning agent.

The dried material is sanded and split, and it becomes a soft, velvety synthetic leather with a weight of approx. Get 220 g / m ² .

Example 3

A fiber mixture of 70% siliconized polyester fibers 1.6 dtex / 40 mm and 30% polyester high-shrink fibers 1.3 dtex / 60 mm is nonwoven according to the method mentioned in Example 2 and aftertreated and refined with a polyurethane solution.

The velvet-like synthetic leather obtained with a weight of approx. 230 g / m ² is noticeably harder to handle and less drapable than the product according to Example 2.

Example 4

• a) Das so vorbehandelte Vlies wird mit einer etwas 23 %igen Latexdispersion (Perbunan N 3415®) imprägniert, Feststoffauftrag ca. 100 % bezogen auf das Vliesgewicht und im IR-Feld koaguliert, dampfvulkanisiert, gewaschen, getrocknet und in Trockenhitze bei 140°C vulkanisiert. Das erhaltene Rohprodukt wird gespalten, beidseitig geschliffen; das erhaltene Velours-Kunstleder kann mit Dispersionsfarben nach den bekannten Färbemethoden eingefärbt werden und eignet sich je nach Dicke für überbekleidung, Polstermaterial oder Schuhoberleder.
• b) Das vorbehandelte Vlies wird mit einer 23 %igen Latexdispersion, bestehend aus 50 % Perbunan N 3415_@ und 50 % Perbunan N Latex KA 8194@ nach dem unter 4a beschribenen Verfahren ausgerüstet; der Feststoffauftrag betrug 100 % bezogen auf das Aufgangsvliesgewicht. Das gespaltene und geschliffene Material kann mit Dispersionsfarben gefärbt werden, es ist im Griff weicher, textilartiger als das Produkt nach a). Das Einsatzgebiet ist Uberbekleidung. Beispiel 5

A fiber mixture of 70% siliconized polyamide fibers 1.6 dtex / 40 mm and 30% polyester high shrink fibers 1.3 dtex / 60 mm is bonded, needled and shrunk according to the method described in Example 2. Fleece weight: ~ 450g / m ²
Puncture density: approx. 800 punctures / cm ² .

• a) The pre-treated fleece is impregnated with a somewhat 23% latex dispersion (Perbunan N 3415®), solids application approx. 100% based on the fleece weight and coagulated in the IR field, steam-vulcanized, washed, dried and in dry heat at 140 ° C vulcanized. The crude product obtained is split, ground on both sides; The velor synthetic leather obtained can be dyed with emulsion paints according to the well-known dyeing methods and, depending on the thickness, is suitable for outerwear, upholstery material or upper leather.
• b) The pretreated fleece is equipped with a 23% latex dispersion, consisting of 50% Perbunan N 3415 _@ and 50% Perbunan N latex KA 8194 @ according to the procedure described under 4a; the solids application was 100% based on the initial nonwoven weight. The split and sanded material can be colored with emulsion paints, it is softer to the touch, more textile than the product according to a). The area of application is outerwear. Example 5

A fiber mixture of 70% silicone-treated and 20% non-silicone-treated polyamide fibers 1.6 dtex / 40 mm approx. (8% residual shrinkage) is nonwoven according to the method described in Example 2, impregnated with the latex types mentioned in Example 4 and further treated.

In both cases, the end products are softer than the end products according to 4a and 4b and have better strength, tear resistance and puncture resistance.

Claims (10)

1. A process for producing a synthetic leather by forming a fleece from staple fibers, the fibers being laid open on a card or a pneumatic fleece-forming system to form a fleece, pressed, preferably needled, optionally shrunk, impregnated with a binder, optionally split, optionally ground, roughened, brushed and optionally coated, characterized in that fibers are used to form the fleece, at least some of which is hydrophobized by impregnation with a hydrophobicizing agent. 2. The method according to claim 1, characterized in that the hydrophobized fibers contain the hydrophobizing agent in an application amount of 0.01 to 5%, preferably from 0.1 to 2%. 3. Process according to claims 1 and 2, characterized in that oils, fats, fatty acid salts, silicones, silicone-containing products or mixtures thereof are used as hydrophobizing agents. 4. The method according to claims 1-3, characterized in that a fiber mixture of hydrophobized and non-hydrophobized fibers is used for the nonwoven formation. 5. The method according to claims 1-4, characterized in that the fleece is at least partially hydrophobized before the impregnation with binders. 6. The method according to claims 1-4, characterized in that the fleece is constructed as a sandwich structure - and the individual layers forming this structure contain at least partially hydrophobized fibers. 7. The method according to claim 6, characterized in that only one layer contains at least partially hydrophobized fibers. 8. The method according to claims 1-7, characterized in that the nonwoven consists of two nonwoven layers, only the fibers of one layer being at least partially hydrophobic and that the needling of the two layers takes place in such a way that, at least during the last needle passage, the needles only from that side occur, which contains the hydrophobized fibers and that the puncture depth is selected such that fiber tufts are pierced on the non-hydrophobizing agent layer facing away from the puncture side and after roughening and brushes form a velvety surface. 9. The method according to claims 6-8, characterized in that the individual layers consist of fibers with different swelling properties. 10. The method according to claims 1-9, characterized in that the proportion of hydrophobic fibers in the fleece is 5-100%, preferably 5-90%.