EP0024511B1 - Coated fabric, process for its manufacture, and its use - Google Patents

Description

The invention relates to a coated fabric with a fabric made of endless multifilament threads, which is coated with two layers of macromolecular substances, a method for its production and its use. Such a coated fabric is known from BE-PS 543 880.

Coated fabrics generally consist of a fabric, knitted fabric, scrim or the like thread structure, or the like with rubber, plastic, resin. is coated, and are usually liquid and air or gas impermeable. The advantages which can be achieved with such coated fabrics can be attributed in particular to the combination of the known favorable properties of the conventional coating materials with the comparatively higher strength of the thread structures embedded therein.

Because of their advantageous properties, coated fabrics are widely used in a wide variety of areas of technology and everyday life, for example for the manufacture of air-filled halls, stadium roofs, packaging material, truck tarpaulins, inflatable boats, roof truss insulation and the like. However, difficulties arose again and again, especially when the adhesion between the fabric and the coating material was insufficient. Better adhesion is generally achieved with fabrics made from spun yarns, which is why such fabrics were often preferred, so that the known advantages of endless multifilament yarns could not yet be fully applied in all areas. In order to meet the sometimes high demands on the strength of the coated fabrics made from spun yarns, in many cases only fabrics with a high fabric density could be used. Particular difficulties arose in particular if, due to special requirements for the coated fabric, the coating material consisted of synthetic resin or a plastic / synthetic resin mixture and high demands were also placed on the strength of the coated fabric. There has been no shortage of attempts to use filament yarns for such purposes, however, all efforts in this regard have so far only led to unsatisfactory results.

The present invention is therefore based on the object of providing a coated fabric in which the adhesion between the fabric consisting of endless multifilament threads and the coating composition consisting partly of synthetic resin is improved such that due to the improved adhesion and the comparatively higher Strength of multifilament continuous filaments, even fabrics with a lower fabric density than previously customary.

This object is achieved by a coated fabric with a fabric made of endless multifilament threads, which is coated with two layers of macromolecular substances, in which, according to the invention, the surface of the endless multifilament threads is activated and roughened to improve the adhesion by chemical action, in which the tissue has a fabric density in the range from 26% to 60%, and in which the first and second layers consist of a plastic / synthetic resin mixture, the proportion by weight of the two mixture components being different in the two layers.

The nature of the first layer ensures excellent adhesion to the carrier fabric, and despite the presence of the second layer, the coated fabric according to the invention has a high degree of flexibility. The nature of the second layer makes it possible to process the coated fabric according to the invention as such or to make it usable for other purposes by further coating.

The present invention therefore makes it possible, using the known advantageous properties of endless multifilament yarns, to keep the proportion of fabric comparatively low without having to accept any loss in the performance properties of the coated fabric according to the invention.

A further improvement in the adhesion between the fabric and the first layer is achieved if the fabric or the threads used for this purpose previously according to one of DE-AS-1 199 224, DE-AS-1 212 245, DE- OS-1 444 139, DE-AS-1 444 140, DE-OS-1 444 141 or DE-AS-1 444 142 have been treated.

According to the invention, both sides of the fabric can also be coated with the same advantages.

For the production of the coated fabric according to the invention, fabrics with a relatively high fabric density of, for example, 60% are suitable, as well as fabrics with a relatively low fabric density of, for example, 26%. However, particularly good results are achieved with fabrics whose fabric density is in the range from 32% to 42%. The method described in the magazine "Textilpraxis", edition 1947, pages 330 to 335 and 366 to 370 is used to determine the fabric density.

Although useful results can be achieved even if the proportion by weight of the plastic in the first layer or in the second layer is only 0.2 times or 10 times the proportion by weight of the synthetic resin in these layers, the proportion by weight is Plastic in the first layer and / or in the second layer but advantageously 1 to 4 times the proportion by weight of the synthetic resin, excellent results being achieved when the proportion by weight of the plastic is 1.5 to 2 times the proportion by weight of the synthetic resin.

In a preferred embodiment of the coated fabric according to the invention, the synthetic resin contained in the first and / or in the second layer is a phenolic resin and / or the plastic contained in the first and / or the second layer is elastic and / or thermoplastic.

A sufficiently high dimensional stability even under tensile stress is achieved if the fabric used has a not too high reference elongation. Good results are already achieved with the coated fabric according to the invention when the reference elongation of the fabric, measured at 55 daN / 5 cm, is below 4% and measured at 90 daN / 5 cm below 8%, although a fabric is preferred in which the corresponding values are below 2% or 4% and excellent results can be achieved if these values are below 1% or below 2%. The reference strain is taken directly from the usual stress-strain diagram of the tensile test according to DIN 53 857 or 53 354.

Although fabrics made from conventional continuous multifilament threads are suitable for producing the coated fabric according to the invention, those made from polyester threads activated and roughened on their surface with the aid of an alkaline reaction partner, and in particular those made from polyethylene terephthalate, are advantageously used. Very good results are also achieved with fabrics made from threads made from aromatic polyamides (abbreviated to "aramid threads").

The advantageous properties of the coated fabric according to the invention are possibly further improved by the fact that at least the second layer contains conventional inorganic fillers with a weight fraction of up to 80% of the respective layer. Such fillers, for example, CaCO _z.

Fabrics in the sense of the present invention are all known fabrics made of fibers and / or threads, for example conventional fabrics, fleeces, laid fabrics, knitted fabrics and the like, the fabric most suitable for the respective purpose being determined quickly and easily by producing appropriate test pieces can be. The fabrics suitable for producing the coated fabric according to the invention generally need not have been subjected to any special pretreatment that goes beyond the usual. However, it is readily possible to use fabrics whose fibers have previously been activated and roughened by chemical action on their surface.

Synthetic resins in the sense of the present invention are highly cross-linked thermoset materials produced by polymerization, polycondensation or polyaddition, also called thermosets, which also include hardeners, plasticizers, catalysts and the like. may have been added. Examples of such synthetic resins are: polyamide, phenol, unsaturated or saturated polyester, epoxy or acrylic resins.

For the purposes of the present invention, plastics are weakly crosslinked dispersible thermoplastic substances which are produced by polymerization, polycondensation or polyaddition and which, after drying, i.e. after removal of the dispersion liquid, for example water, preferably have a rough surface structure. For example, plastics based on the following are suitable: acrylic, acrylic acid esters, acrylonitrile copolymers, polyvinyl acetate, epoxy and the like.

The synthetic resins and plastics suitable for the coated fabric according to the invention can also be chemically related, i.e. belong to the same chemical system.

The flexibility or rigidity of the coated fabric according to the invention can be adapted to the respective requirements by a suitable choice of the mixing ratio of plastic and synthetic resin in the coating mixtures.

The first layer acts as an elastic film former with good film formation on the carrier fabric, so that the second layer is prevented from penetrating too deeply into the carrier fabric, as a result of which a high flexibility of the coated fabric according to the invention is achieved.

The determination of the plastic or synthetic resin content in the two layers of a sample is possible, for example, by making several sample strips with different proportions of the two mixing partners and then carrying out comparative measurements on the sample and the sample strip.

In order to produce the coated fabric according to the invention, the customary and known methods can generally be used, in which the layers are coated in succession by doctoring, by application rollers, in immersion baths and the like. are applied in succession to the carrier fabric, wherein after the application of a layer, this layer is optionally dried in whole or in part and / or is allowed to set or harden. The carrier fabric can be subjected to a chemical treatment beforehand, by means of which the threads or fibers used for the carrier fabric are activated and roughened on their surface. However, it has proven to be particularly advantageous to combine the process of activation and roughening with the application of the first layer.

It is therefore proposed, in order to produce the coated fabric according to the invention, to apply the two layers one after the other onto the top and / or bottom of the fabric in a manner known per se and, according to the invention, to use a fabric made of endless multi as a carrier fabric to use filaments with a fabric density in the range of 26% to 60% and at least the mixture consisting of a plastic and a synthetic resin intended to form the first layer, in which the percentage by weight of the plastic is one to four times the percentage by weight of the synthetic resin, a chemical reactant activating and roughening the surface of the multifilament threads of the fabric to improve the adhesion, wherein the mixture intended to form the first layer is admixed with a larger proportion of the chemical reactant than the mixture intended to form the second layer, based in each case on the total amount each individual mixture, in the mixture consisting of a plastic and a synthetic resin intended to form the second layer, the weight fraction of the two mixture components being set to be different in size compared to the mixture intended to form the first layer.

The mixtures intended for the two layers preferably consist of a mixture of an aqueous colloidal plastic dispersion and a water-soluble synthetic resin and the appropriate chemical reactant. A mixture consisting of an acrylic-based plastic, in particular acrylonitrile and acrylic acid ester copolymers, and a water-soluble synthetic resin based on phenol-formaldehyde has proven particularly useful.

Fillers can also be added to the layer mixtures. Depending on the type and amount of the particularly preferred inorganic fillers, the application of the first layer on the top and bottom of the fabric may be appropriate.

To improve the wettability of the fabric, customary wetting agents can also be added to the mixtures intended to form the two layers.

When using a fabric consisting of polyester threads, in particular such threads made of polyethylene terephthalate, the roughening and activation of the thread surface is usefully achieved when the mixture intended for the first layer has a pH in the range from 8 to 14 and that the mixture intended for the second layer is adjusted to a pH in the range from 7 to 14. This can be achieved, for example, by adding an appropriate amount of sodium hydroxide solution (NaOH) or ammonia (NH3) to the plastic / synthetic resin mixture. The alkalinity of the mixture intended to form the second layer can in this case be set to an equally high or even higher pH than that of the mixture intended for the first layer, but it is preferably set to a lower pH. Particularly good results are achieved when the mixture intended for the first layer is adjusted to a pH in the range from 10 to 14 and the mixture intended for the second layer to a pH in the range from 8 to 12, with excellent results can be achieved when the pH for the two layer mixtures mentioned is in the range from 12 to 13 or from 9 to 11. It is possible here to add different chemical reactants to the individual mixtures intended to form the two layers, for example one mixture of sodium hydroxide solution and the other ammonia.

The coated fabric according to the invention can be used in a variety of different ways due to the excellent adhesion between the base fabric and the coating material, as well as its great flexibility, high strength and low reference elongation. Because of the advantageous properties mentioned, it is also particularly suitable for the production of all types of abrasives, which can advantageously be used for both dry and wet grinding processes, the coated fabric according to the invention also being outstandingly suitable for producing endless grinding belts. When using the coated fabric according to the invention for the production of abrasives, it has a particularly advantageous effect that an excellent adhesion of the grain binder layer to the second layer is achieved.

The invention will now be explained in more detail with reference to the drawing and the following examples:

The figure shows a simplified representation of an embodiment of the coated fabric according to the invention in section.

In this embodiment, the fabric 1 made of endless multifilament threads is provided with a first layer 2 both on the top and on the bottom. The coating material forming the first layer 2 is partly also penetrated into the gaps existing between the individual multifilament threads of the fabric 1 and partly also between the individual filaments of the threads. The second layer 3 is applied to the top of the fabric 1 above the first layer 2. The finished coated fabric thus has an essentially smooth surface, while the underside still reveals the structure of the embedded fabric 1.

example 1

A fabric made of endless multifilament threads made of polyethylene terephthalate was used to produce a coated fabric according to the invention, the threads having the following properties:

This fabric was provided on both sides with a first layer, with the coating mixture being applied to both sides so much that the application quantity in the finished product was 50 g / m ² on the front and 35 g / m ² on the back.

• 20 Gewichtsteile einer wäßrigen Kunststoff-Dispersion bestehend aus 48 Gew.-% eines Kunststoffes auf Acrylbasis (Feststoffanteil) und 52 Gew.-% Wasser;
• 10 Gewichtsteile einer Lösung bestehend aus 70 Gew.-% modifiziertem Phenol-Resol-Harz (Feststoffanteil) und 30 Gew.-%

The mixture intended to form the first layer had the following composition:

• 20 parts by weight of an aqueous plastic dispersion consisting of 48% by weight of an acrylic-based plastic (solids content) and 52% by weight of water;
• 10 parts by weight of a solution consisting of 70% by weight of modified phenol resole resin (solids content) and 30% by weight

Water with a common solvent and 1.5 parts by weight of a 6% aqueous NaOH solution.

• 10 Gewichtsteile einer wäßrigen Kunststoffdispersion wie für die erste Schicht verwendet (s.oben);
• 20 Gewichtsteile einer wäßrigen Kunstharzlösung wie für die erste Schicht verwendet (s.oben);
• 0,5 Gewichtsteile einer 6%-igen wäßrigen NaOH-Lösung sowie 1 Gewichtsteil eines üblichen Benetzungsmittels.

The fabric with the first layer applied on both sides was exposed to a temperature of 90 ° C. for 3 minutes. The second layer was then applied to the top of the fabric coated in this way. The mixture intended for this had the following composition:

• 10 parts by weight of an aqueous plastic dispersion as used for the first layer (see above);
• 20 parts by weight of an aqueous synthetic resin solution as used for the first layer (see above);
• 0.5 part by weight of a 6% aqueous NaOH solution and 1 part by weight of a conventional wetting agent.

So much of this mixture was applied that the application amount of the second layer in the finished product was 20 g / m ² . After the mixture for the second layer had been applied, the coated fabric of the invention thus formed was exposed to a temperature of 90 ° C. for 3 minutes.

Example 2

While maintaining the other data and process parameters as in Example 1, a coated fabric according to the invention was produced in the following manner or with the following properties:

• Auftragsmenge (nur Vorderseite) im fertigen Produkt: 80 g/m²
• Aushärtungs-bzw. Trocknungsbedingungen: 3 Minuten bei 100°C
• Das für die zweite Schicht bestimmte Gemisch enthielt zusätzlich 10 Gewichtsteile CaC0₃;
• Auftragsmenge im fertigen Produkt: 30 g/m^z
• Aushärtungs-bzw. Trocknungsbedingungen: 2 Minuten bei 100°C

The mixture intended for the first layer also contains 1.5 parts by weight of a conventional thickener.

• Order quantity (front only) in the finished product: 80 g / m ²
• Curing or Drying conditions: 3 minutes at 100 ° C
• The mixture intended for the second layer additionally contained 10 parts by weight of CaCO ₃ ;
• Order quantity in the finished product: 30 g / m ^z
• Curing or Drying conditions: 2 minutes at 100 ° C

Example 3

• Gewebe: wie Beispiel 2;
• Das für die erste Schicht bestimmte Gemisch enthielt im Vergleich zu Beispiel 1 zusätzlich 0,8 Gewichtsteile eines herkömmlichen Verdickungsmittels sowie zusätzlich 10 Gewichtsteile eines herkömmlichen Füllmittels; die Auftragsmenge auf der Vorderseite betrug im fertigen Produkt 70 g/m², wobei Dauer und Temperatur für die Aushärtung 3 min. bzw. 90°C betrugen; die Auftragsmenge auf der Rückseite betrug im fertigen Produkt 40 g/m², wobei hierfür die Dauer für die Aushärtung 2,5 min. und die Temperatur dafür 85°C betrug.

In a further test, a coated fabric according to the invention was produced in the following way:

• Fabric: as example 2;
• The mixture intended for the first layer contained an additional 0.8 parts by weight of a conventional thickener and an additional 10 parts by weight of a conventional filler compared to Example 1; the application quantity on the front side was 70 g / m ² in the finished product, the duration and temperature for curing being 3 minutes. or 90 ° C; the application quantity on the back was 40 g / m ² in the finished product, the duration for curing being 2.5 min. and the temperature for this was 85 ° C.

The second layer corresponded to that of Example 2.

Example 4

Here, a fabric made of endless multifilament threads made of polyethylene terephthalate was used, which had the following properties:

This fabric was provided with a first layer on both sides, with enough of the mixture being applied to both sides that the application quantity in the finished product was 80 g / m ² on the front and 35 g / m ² on the back.

• 25 Gewichtsteile einer wäßrigen Kunststoffdispersion wie in Beispiel 1 beschrieben;
• 5 Gewichtsteile einer Kunstharzlösung wie in Beispiel 1 beschrieben;
• 1,5 Gewichtsteile einer wäßrigen NaOH-Lösung wie in Beispiel 1 beschrieben, sowie
• 1 Gewichtsteil eines üblichen Verdickungsmittels.

The mixture intended to form the first layer had the following composition:

• 25 parts by weight of an aqueous plastic dispersion as described in Example 1;
• 5 parts by weight of a synthetic resin solution as described in Example 1;
• 1.5 parts by weight of an aqueous NaOH solution as described in Example 1, and
• 1 part by weight of a conventional thickener.

• 10 Gewichtsteile einer wäßrigen Kunststoffdispersion wie in Beispiel 1 beschrieben;
• 25 Gewichtsteile einer wäßrigen Kunstharzlösung wie in Beispiel Beispiel 1 beschrieben;
• 0,2 Gewichtsteile einer wäßrigen NaOH-Lösung wie in Beispiel 1 beschrieben;
• 0,5 Gewichtsteile eines üblichen Benetzungsmittels sowie 15 Gewichtsteile CaC0₃.

The fabric with the first layer applied on both sides was 3 min. exposed to a temperature of 90 ° C for a long time. The second layer was then applied to the top of the fabric coated in this way. The mixture intended for this had the following composition:

• 10 parts by weight of an aqueous plastic dispersion as described in Example 1;
• 25 parts by weight of an aqueous synthetic resin solution as described in Example 1;
• 0.2 parts by weight of an aqueous NaOH solution as described in Example 1;
• 0.5 part by weight of a conventional wetting agent and 15 parts by weight of CaC0 ₃ .

So much of this mixture was applied that the application amount of the second layer in the finished product was 30 g / m ² . After the mixture for the second layer had been applied, the fabric thus coated was exposed to a temperature of 90 ° C. for 3 minutes.

Example 5

Here, a fabric made of endless aramid multifilaments with a titer of 1200 dtex f 750 was used to produce a coated fabric according to the invention. The fabric was bound in plain weave. It was:

The mixture intended for the first layer corresponded to that described in Example 1, with the exception that 0.8 part by weight of a 6% strength aqueous NaOH solution was admixed with it. The heat treatment of the fabric provided with the first layer also corresponded to that described in Example 1.

• 10 Gewichtsteile einer wäßrigen Kunststoffdispersion wie in Beispiel 1 beschrieben;
• 20 Gewichtsteile einer wäßrigen Kunstharzlösung wie in Beispiel 1 beschrieben;
• 15 Gewichtsteile CaC0₃ sowie 0,2 Gewichtsteile einer 6%-igen wäßrigen NaOH-Lösung.

The mixture intended for the second layer had the following composition:

• 10 parts by weight of an aqueous plastic dispersion as described in Example 1;
• 20 parts by weight of an aqueous synthetic resin solution as described in Example 1;
• 15 parts by weight of CaC0 ₃ and 0.2 parts by weight of a 6% aqueous NaOH solution.

The application amount of the second layer in the finished product was 30 g / m ² , the curing or drying conditions were: 3 min. and 95 ° C.

Example 6

The fabric used here was a mixed fabric of endless polyester multifilament threads as weft threads and endless aramid threads as warp threads. The polyester threads had a titer of 1100 dtex f 210, their density was 9 threads / cm. The aramid threads had a nominal titer of 420 dtex f 250, their thread density in the fabric was 18 threads / cm. The fabric was bound in plain weave and had a weight per unit area of 200 g / m ^2.

The corresponding values for the polyester threads are listed in Example 4.

The remaining data and process parameters corresponded to those of Example 5.

Example 7

To demonstrate that the coating proposed according to the invention can also be carried out using fabrics made from fiber yarns, a fabric made from an aramid fiber yarn with a titer of 1200 dtex was used. The thread density of both the warp and the weft threads in the finished fabric was 9 threads / cm, which corresponds to a fabric density of 34% and a basis weight of 220 g / m ² .

The fabric was bound in plain weave.

The other process parameters and data corresponded to those of Example 5.

Abrasives with excellent properties were produced from all of the coated fabrics according to the invention produced according to the examples given.

Claims (16)

1. A coated fabric having a fabric consisting of continuous multifilament yarns, which is coated with two layers consisting of macromolecular substances, characterised in that the surface of the continuous multifilament yarns is activated and roughened to improve the adhesion thereof by the effect of chemicals, the fabric has a density which ranges from 26% to 60% and the first and second layers consist of a plastics/synthetic resin mixture, the weight proportion of the two components of the mixture varying in the two layers.

2. A coated fabric according to claim 1, characterised in that the weight proportion of the plastics material amounts to from 1 to 4 times the weight proportion of the synthetic resin.

3. A coated fabric according to claim 1, characterised in that the weight proportion of the plastics material amounts to from 1.5 to 2 times the weight proportion of the synthetic resin.

4. A coated fabric according to claims 1 to 3, characterised in that the plastics material is elastic and/or thermoplastic.

5. A layered fabric according to claims 1 to 4, characterised in that the fabric density ranges from 32 to 42%.

6. A coated fabric according to claims 1 to 5, characterised in that the fabric has a reference extension-measured at 55 daN/5 cm and 90 daN/5 cm-of less than 4% or 8%.

7. A coated fabric according to claims 1 to 6, characterised in that the reference extension of the fabric is less than 2% or 4%.

8. A coated fabric according to claims 1 to 6, characterised in that the reference extension of the fabric is less than 1 % or 2%.

9. A coated fabric according to claims 1 to 8, characterised in that the fabric consists of polyester yarns the surfaces of which have been activated and roughened by means of an alkaline reaction component.

10. A coated fabric according to claims 1 to 8, characterised in that the fabric consists of aramide yams.

11. A coated fabric according to claims 1 to 10, characterised in that the synthetic resin is a phenol-formaldehyde resin.

12. A process for the production of the coated fabric according to claims 1 to 11, in which the two layers which consist of macromolecular substances are successively applied in a known manner to the upper and/or lower side of the fabric consisting of continuous multifilament yarns, characterised in that a fabric having a density ranging from 26% to 60% is used, a chemical reaction component which activates and roughens the surface of the multifilament yarns to improve the adhesion thereof is admixed with at least the mixture which is intended to constitute the first layer and which consists of a plastics material and a synthetic resin, and in which the weight proportion of the plastics material amounts to from 1 to 4 times the weight of the synthetic resin, a larger weight proportion of the chemical reaction component being admixed with the mixture which is intended to constitute the first layer, than to the mixture which is intended to constitute the second layer, based, in each case, on the total quantity of each individual mixture, and the second layer is constituted by a mixture consisting of a plastics material and a synthetic resin, a mixture in which the weight proportion of the two components of the mixture varies with respect to the mixture which is intended to constitute the first layer.

13. A process according to claim 12, characterised in that a fabric consisting of polyester yarns is used and the mixture which is intended to constitute the first layer is adjusted to a pH value which ranges from 8 to 14 and the mixture which is intended to substitute the second layer is adjusted to a pH value which ranges from 7 to 14.

14. A process according to claim 12, characterised in that the mixture which is intended for the first layer is adjusted to a pH value which ranges from 10 to 14 and the mixture which is intended for the second layer is adjusted to a pH value which ranges from 8 to 12.

15. A process according to claim 12, characterised in that the mixture which is intended for the first layer is adjusted to a pH value which ranges from 12 to 13 and the mixture which is intended for the second layer is adjusted to a pH value which ranges from 9 to 11.

16. The use of the coated fabric, according to claims 1 to 11, for the production of abrasives.

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