CN1446281A - Coated flexible fabric - Google Patents

Abstract

The invention relates to an embossed, PUR system-coated textile fabric, to a method for producing the same and to the use of a fabric of this type as a decorative starting material. The inventive fabrics, which have a residual shrinkage, are coated with PUR and then post-treated using heat.

Description

Coated Flexible Fabric

The invention relates to a texture surface polyurethane coated textile fabric, its production method and its application as a decorative raw material.

The production of coated textile fabrics, for example the production of synthetic leather, is a known technology for a long time. The coating composition is applied to the substrate in one or more layers, either directly or by transfer methods. Coated textile fabrics are especially useful in the production of outerwear, shoe uppers and linings, luggage making materials and various upholstery materials as well as automotive interiors.

Coated textiles or other fabrics are often grained or embossed using the following methods known to those skilled in the art, all of which have disadvantages:

- Embossing a defined pattern onto the coated substrate by the action of heat and pressure applied to an embossing roll, embossing plate or transfer paper. Such embossing produces texture, but the local compression causes undesirable hardening. These more costly methods uniquely use a thermoplastic polyurethane solution that still contains some solvent that evaporates under the action of heat.

- Uncontrolled grain patterns can be produced by treating material coated with a two-pack of polyurethane solution, provided that the material is placed in an orbiting dryer with alternating directions of movement at e.g. 20 to 100 °C for a certain period of time (see for example DE-A 1 760 260). The disadvantage of this method is not only the use of organic solvents, but also the need to precisely observe the processing time, which means that the formation of the texture must be completed before the actual crosslinking of the system.

- The rotary method (Umkehrverfahren) utilizes a textured release material, especially release paper or a silicone template, to produce the embossed surface. However, embossing produced with release paper is relatively flat and must be predetermined during the actual coating step. The use of siloxane templates is very costly and is no longer acceptable except for special effects.

The object of the present invention is to provide a method for producing deep textures on textile fabrics which overcomes the above-mentioned disadvantages, thereby obtaining high-quality products with simple operations.

Surprisingly, it has now been found that coated fabrics with textured surface formation can be obtained by first coating textile fabrics with residual shrinkage with polyurethane dispersions or solutions, directly or in a rotary process, and then by subjecting them to heat treatment.

Accordingly, the present invention provides a method for producing a textured textile fabric, characterized in that the fabric having residual shrinkage is coated with a polyurethane dispersion or solution and then subjected to a thermal post-treatment.

The invention also provides a textured topcoated textile fabric obtainable by the method of the invention.

Textile fabrics within the scope of the present invention mean, for example, woven and knitted fabrics and bonded and unbonded fiber webs and microfibrous webs. These materials may be composed of synthetic, natural and/or mixtures thereof. In addition to textiles composed of any fibers, all other textile fabrics can in principle also be used in the process according to the invention, provided they have residual shrinkage.

The residual shrinkage of textile materials consisting of fiber blends with polyester fiber fractions can be increased by cracking, since cracking reduces the polyester fiber content and thus the stiffer fabric content.

To create very deep grain profiles, it has proven to be advantageous to fill and reinforce the textile fabric by curing the polyurethane prior to polyurethane coating, and this is therefore a preferred embodiment of the invention.

Particularly useful systems for the pretreatment of fabrics by coagulation are reactive or postcrosslinked polyurethane dispersions, as described, for example, in WO 00/34352. A polyurethane dispersion consisting of blocked isocyanate groups and at least one polyamine is precipitated by heat treatment to form a stable, partially crosslinked polyurethane or gel.

Coagulation is particularly useful for film formation, for coating a wide variety of materials or for partially or completely impregnating fibrous webs, knits or other fabrics for reinforcement purposes.

The reactive, postcrosslinkable polyurethane dispersions can be applied, for example, by casting, spraying, dipping, spraying, padding, using a doctor blade, roller or padding machine, the dispersions being available in liquid or foamed state .

In general, after application by one of the above-mentioned methods, by immersing in hot water at 50°C to 120°C, preferably 75°C to 98°C or using hot steam or in an oven, using radiation or High-frequency drier for coagulation, followed by drying at 60°C to 180°C, preferably 100°C to 140°C, and baking at 140°C to 165°C.

The fabric should be tentered during crosslinking and drying to avoid premature shrinkage of the fabric.

The coagulum formed is sufficiently strong that the precipitation operation after application can even be carried out in a saponification or cracking bath (3% sodium hydroxide), and in the case of, for example, microfibrous webs with polyester fractions, the fractions It can be saponified and dissolved simultaneously. This produces a particularly soft fabric with a pleasant hand.

The coated or filled fabric can also be subsequently buffed and thus made particularly soft. Softness can be further improved by mechanical treatment in a drum.

It is also possible to perform other aqueous medium coagulation processes to achieve reinforcement prior to the method of the invention, for example, electrolyte or thermal coagulation of the dispersion.

Electrolyte coagulation is performed by immersing the coated substrate in a concentrated salt solution or in a bath such as acidified water, whereupon the binder will set under the action of the high electrolyte concentration.

In thermal setting, non-post-crosslinkable binders formulated to be heat sensitive are set using elevated temperatures.

The precleaned and optionally reinforced textile fabric is then coated with a polyurethane system in a known manner directly or by the rotary process.

Coatings suitable for the process according to the invention are, for example, the one-pack and two-pack polyurethane systems known from the textile and leather industry, which consist of isocyanate prepolymers and crosslinkers and are commercially available in solution.

Coatings suitable for the method of the invention also include the polyurethane one-pack aqueous dispersions disclosed in DE-A 4 236 569 which additionally comprise hydrophilizing structures.

Particularly useful are solvent-free two-pack polyurethane systems consisting of blocked isocyanate prepolymers and polyamines, as disclosed, for example, in EP-A 0 784 097. Such systems have good wet adhesion and excellent water resistance. Mixtures of various polyurethane systems are also suitable.

Coatings based on the polyurethane dispersions disclosed in DE-A 42 36 569 can improve the wearing comfort of coated fabrics, because the coatings produced with such polyurethane dispersions are water vapor permeable.

In the direct method, polyurethane coatings are applied directly to the substrate using a doctor blade, roller or bar.

In general, multiple, but preferably two, coatings are applied one after the other such that the total thickness of the coating consisting of basecoat and topcoat is 10-100 μm, preferably 20-60 μm. The base coat can also be a paste that dries to form a microporous layer, such as disclosed in DE-A 2 020 153. The topcoat applied subsequently protects the entire unit against mechanical wear and tear.

The overall coating of basecoat and topcoat can also be applied by the rotary method.

The rotary method is advantageous when using very soft substrates such as knitted fabrics, fibrous webs or other discontinuous fabrics.

In the rotary process, the initial step is to apply the topcoat by doctor blade to a textured or non-textured transfer paper and dry. Then, optionally and preferably, a foamed intermediate layer is applied. After the second primer or adhesive coat has been applied, the substrate is lightly pressed into this still wet layer. After drying, a strongly bonded monolith of coating and substrate is obtained, which is separated from the release carrier, the structure of which then corresponds substantially to that of the direct-applied coating described above. A coated, and optionally, surface-grained article, depending on the transfer paper, is obtained after the crosslinking step.

In this state, the coated fabric can be stored dry and processed at a later time, at which point the article can then be given the desired texture and colour.

Simple pre-embossing of fabrics coated according to the invention can result in a certain texture pattern, since the depressions created in the pre-embossing form a corresponding, but deeper, texture under the action of heat in the post-treatment. Without such pre-embossing, post-processing will produce a product with a more random texture.

Directly coated fabrics can optionally be slightly pre-embossed by means of embossing or creping calender rolls.

In the case of the rotary method, a textured pattern of pre-embossing can be produced using a textured transfer paper. Unstructured release paper or simple mat calender rolls will produce a random texture in post processing.

Post-treatment of coated textile fabrics includes subsequent dyeing operations, or tension-free boiling water treatment. In the case of treatment with hot water, it is also possible to add suitable pigments directly to the coating composition.

Depending on the composition of the substrate, coatings and substrates can be dyed with acid, disperse or metal complex dyes. Low-tension, high bath ratio (Langem Flottenverhältnis) dyeing processes, as provided by eg winch dyeing tanks, are particularly useful. Metal complex dyes, either directly or via lakes, produce excellent wet fastness in polyurethane coatings.

After the drying operation, the fabrics are optionally neutralized and rinsed thoroughly. Adding a finish to the final cleaning bath is one way to utilize the finish to improve the hand before the material is tension-free dried. When using cellulose based materials it is advisable to send them through a drum to eliminate any possible wet-stiffness.

The fabric of the present invention can be used as a decorative raw material, for example, as an outerwear material, as a shoe upper material and lining, as a bag manufacturing material and various cushion materials, and as an automobile interior material.

Embodiment 1, the pretreatment embodiment 1 of cleaning textile fabric (the present invention)

Utilize the enhanced bath liquid of the aqueous medium coagulation of reactive dispersion: Impranil® ^VP LS 2333 (Bayer Company, 90～180 parts by weight Leverkusen) 1～2.7 parts by weight ^Imprafix® VP LS 2330/isopropanol (1:1 )(bye

                    Deionized water

The solids content of the dispersion bath is 4-8%.

The textile fabrics were treated with a bath of the dispersion on a padder (100% absorption) and subsequently coagulated in an evaporator at 98°C.

Complete crosslinking and drying were carried out on a tenter frame at 165°C.

In the case of the use of fibrous webs, for example composed of polyester and polyamide fiber blends, cracking can optionally be carried out during or after setting in order to obtain a soft hand. For this purpose, the fiber web is treated, for example, in a 3% sodium hydroxide solution at boiling for about 1 h, as a result of which the polyester is partially dissolved.

Pre-polishing of the substrate surface will intensify this effect. Embodiment 2 (the present invention)

Enhanced bath utilizing coagulation of conventional dispersions: 200 parts by weight of Impranil® ^DLV dispersion (Bayer, Leverkusen)

4 parts by weight ^Koagulant® WS (20%) (Bayer, Leverkusen)

16 parts by weight of sodium chloride aqueous solution (10%)

4 parts by weight ^Euderm® Driver DE (Bayer, Leverkusen)

2 parts by weight of ^Bayderm® Fix CIN (Bayer Corporation, Leverkusen)

774 parts by weight water

The textile fabrics were treated with a dispersion bath (100% absorption) on a padder and subsequently dried on a tenter frame.

Cleavage of polyester/polyamide webs can be carried out in a similar manner to Example 1. Embodiment 3 (the present invention)

In the absence of coagulation to strengthen the textile fabric, it is recommended to dry the cleaned and scoured textile on a tenter frame. II. Coating Example 1 (the present invention): top coat : 650 parts by weight of Impranil ^® DLN dispersion (Bayer Corporation,

Leverkusen)

350 parts by weight of Impranil® ^DLF dispersion (Bayer Corporation,

Leverkusen)

500 parts by weight ^{of Impranil ® DLN} dispersion (Bayer Corporation,

Leverkusen)

500 parts by weight of ^Imprani1® VP LS 2333 (Bayer Corporation,

Leverkusen)

7.5 parts by weight of ^Imprafix® VP LS 2330 (Bayer Corporation,

Leverkusen)/isopropanol (1:1)

20 parts by weight ^Stockal® STA (Stockhausen Krefeld)

30 parts by weight ^Stockal® SR (Stockhausen Krefeld)

Mechanically foam to 500g/L and use ^Mirox® AM (Stockhausen

Krefeld) thickened in the presence of ammonia. Adhesive coating : 1000 parts by weight of ^Impranil® VP LS 2333 (Bayer Corporation,

Leverkusen)

15 parts by weight of ^Imprafix® VP LS 2330 (Bayer Corporation,

Leverkusen)/isopropanol (1:1)

Thickened with Mirox ^(R) AM (Stockhausen Krefeld) in the presence of ammonia.

Coating can be carried out not only by the direct method but also by the rotary method.

During rotary coating with embossed transfer paper, the pattern of the coating can be predetermined by the structure and deepened or accentuated by post-processing.

When choosing a smooth transfer paper, the pattern produced by post-processing is as random as that produced by direct coating. III. Post-treatment of coated textile fabrics

Suitable pigments can also be added directly to the coating paste when the coated textile is aftertreated only with hot water.

Polyurethanes are typically dyed with metal complex dyes (eg, complexed azo dyes, porphyrins, or phthalocyanines) and selected acid and disperse dyes (eg, azo, triarylmethane, or anthraquinone dyes). Depending on the dyeing method and substrate, these dyes can also be used in combination with other types of dyes in the case of tone-on-tone dyeing of the substrate.

The following specific parameters represent a possible way of implementing a simple dyeing in e.g. a winch dyeing tank:

Embodiment (the present invention) dyestuff used

^Telon® dyes (Dystar, Leverkusen) monosulfonic acid dyes

Isolan ^S® dyes (Dystar, Leverkusen) 1:2 metal complex dyes

Bath ratio : 1:40 deionized water

Dye concentration : 2-4% by weight Temperature profile during dyeing :

  40°C30 minutes100°C60 minutes100°C

In the case of dyeing with acid dyes, adjust the pH to 5 with acetic acid.

It is then neutralized with aqueous sodium hydroxide solution and rinsed with deionized water, and finally dried in the tenter state, for example on a ring dryer (Höngeschleifentrockner).

Claims (8)

1. A method of producing textured fabric, characterized in that, the textile fabric with residual shrinkage is first coated with polyurethane dispersion or solution, and then heated for aftertreatment. 2. The method according to claim 1, characterized in that the coating of the textile fabric is carried out by the direct method or the rotary method. 3. The method according to claim 1, characterized in that the textile fabric is reinforced with a reactive and postcrosslinkable polyurethane dispersion by coagulation in an aqueous medium prior to the polyurethane coating. 4. The method according to claim 1, characterized in that the textile fabric is pre-embossed after the polyurethane coating. 5. The method according to claim 1, characterized in that the post-treatment of the coated textile fabric is carried out in a dyeing operation or in a tension-free hot water treatment. 6. Textured topcoat fabric obtainable by the method of claim 1. 7. The fabric of claim 6 is used as a decorative raw material. 8. The fabric of claim 6 is used as an outerwear material, as a shoe upper material and a lining, as a bag material and various cushions, and as an application of an automobile interior material.