DE2709553A1 - PROCESS FOR JOINING TEXTILE STRAPS, CONVEYOR TAPES, FABRICS, ETC. WITH THE HELP OF A POLYURETHANE COMPOUND - Google Patents

Description

HEINZ H. PUSCHMANN · PATENT ADVOCATE

D 8000 MUNICH 22 THOMAS-WIMMER-IUNC 14

TELEPHONE 089/227887

BBA GROUP LIMITED * »'Munich, March 2nd, 1977

Whitechapel Road, P 459/77

P.O.Box No. 20, PuAe

Cleckheaton,

West Yorkshire BD19 6HP,

England

Method for joining textile belts, conveyor belts, fabrics, etc. with the help of a polyurethane compound

709836/0994

The invention relates to the method for connecting textile belts, conveyor belts, fabrics and the like with the aid of a polyurethane connection, in which the ends of the tape or fabric parts to be connected to one another with a liquid casting resin mixture be coated at about room temperature, wonsdi the Cast resin mixture hardens by the action of heat and thus results in the polyurethane compound.

The method according to the invention is suitable for joining textile fabrics, for example belts or tapes, which from cotton or other fibers, from hair, flax, rayon or other synthetic fibers, for example from polyamide or polyester fibers or from mixtures of two or more such types of fibers.

The method according to the invention is particularly suitable for joining multiple fabrics, as they are, for example Used for conveyor belts and the like, and that is woven in such a way that it cannot be broken down into individual layers.

A few methods are already known for joining such fabrics, but in all of them either the joining point itself is deficient or the method of making the connection is unsatisfactory. For example, it is known to join textile fabrics of this type by means of metal connectors or by sewing, but it turned out that that the strength at the junction is significantly below that of the rest of the tissue, and that also the Flexibility of the belt is significantly impaired.

According to British patent specification 705 303, the respective to be connected ends of a belt or fabric provided with mutually offset V-shaped notches so that when the ends are joined together, they interlock with one another in such a way that one at each of the adjacent edges

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A small gap remains in which a suitable polyvinyl compound is used as an adhesive
is cured for a long time.

Binding introduced as an adhesive and at 160 ⁰ C for a few minutes

As an improvement over this process, it is proposed according to British patent specification 901 197 to use a liquid polyurethane casting compound instead of the polyvinyl compound. Although the connection with this material has a longer service life, it has been found to be disadvantageous that polyurethane is sensitive to moisture, so that the ends to be joined must be dried before the connection. Another disadvantage of polyurethane is that, because of its short reaction time, it has to be mixed immediately before use. Further, it must, in order to achieve the best physical properties, the joint can be cured over a period of three hours at a temperature of 10O ⁰ C.

In many cases, it is difficult to carry out in practice to apply such a long curing time and the ones to be joined together To dry the ends beforehand so that the polyurethane connection point is not foamed and thereby a much smaller one Has tensile strength. To circumvent these difficulties, British patent 10 79 136 is a Method described in which, starting from a not completely water-saturated fabric, the edges of the V-shaped notches can be provided with a solid, meltable polyurethane coating, which is then inserted under the ends after the ends have been pushed into one another Heat and pressure is welded.

The object of the invention is to create a method for joining the edges of textile fabrics, for example in tape form, which is free from the disadvantages of known methods in which the curing time is significantly reduced and in which the Curing does not necessarily have to take place under pressure.

Based on a procedure of the type mentioned above

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this object is achieved according to the invention in that at least one component in its cast resin mixture chemical reaction is blocked in such a way that the casting resin mixture does not harden at room temperature, and that the hardening by the action of heat at the ends to be connected only at a temperature above room temperature begins after the two ends butt have been put together.

According to a further feature of the invention is a method for connecting textile tapes or fabrics with the aid a polyurethane connection, characterized in that the two tape or fabric ends to be connected to one another be provided over their entire width with positively matching, preferably V-shaped notches, and that the so notched ends are pushed together so that a narrow gap remains between the notches, in the one liquid casting resin mixture is poured in at room temperature, which hardens to a polyurethane compound through the action of heat, and that the casting resin mixture has at least one component which blocks its chemical reaction in this way is that the casting resin mixture does not harden at room temperature, and that the casting resin mixture is in the gap to connect the ends is cured by the action of heat at a temperature above room temperature.

The polyurethane compound applied to a fabric at room temperature is a mixture, the individual components of which have a relatively low chemical reactivity. This has the great advantage that the mixture is produced at a lower temperature than the curing temperature and over can be stored for a long period of time without hardening before use. This is especially important when the tissue connection is to be established at the place of use, for example on a machine that is difficult to access.

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In addition, since the mixture hardly noticeably reacts at room temperature to form the polyurethane compound, remains the adhesive has a constant viscosity that does not change over the entire surface to be connected until it has hardened begins.

The liquid casting mixture can be composed of one or more polyisocyanates with one or more polyactive hydrogen-containing compounds, in which the active Hydrogen groups are not chemically reactive at room temperature and the liquid pourable mixture is at Can be hardened under the influence of heat and results in an elastomeric polyurethane. The polyisocyanates can each be a simple Be polyisocyanate, for example 2.4 tolylene diisocyanate, m-phenylene diisocyanate, 1.5 naphthalene diisocyanate or triphenylmethane triisocyanate; but it can also be a compound with a higher molecular weight in which free isocyanate groups are present, for example the reaction product of a polytetramethylene glycol with 2,4 tolylene diisocyanate in a molecular ratio of 1: 2 (such compounds with a higher molecular weight are common and are described below referred to as polyurethane prepolymer).

The term "active hydrogen" refers to hydrogen atoms that are released according to the Zerewitinoff method as described by Kohler in the Journal of the American Chamical Society 49, 3181 (1927). These hydrogen atoms react with isocyanate groups and enable the formation of polymeric chains or cross-links. By a chemical barrier to the active hydrogen atoms, the reaction of the active hydrogen is stopped until they regain their chemical reactivity by heating.

An example of a compound with polyactive hydrogen which can be chemically blocked in such a way that the active Not hydrogen at relatively low temperatures

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is activated, is methyldianiline complexed with sodium chloride.

The active hydrogen-containing compound is chemically blocked when the mixture hits the tape at room temperature or tissue is applied, with no change in the viscosity of the mixture as a result of the application chemical reaction occurs. The reactivity of the active hydrogen containing compound causing curing Polyurethane prepolymer or polyisocyanate is added, can therefore, if not rendered ineffective, be very high, and it is also particularly desirable to have a highly reactive active hydrogen containing Compound to use, because then the chemical reactions between the polyisocyanate or polyurethane prepolymer and hardener very quickly as soon as the mixture is heated to break the chemical blocking. Compared to that in British Patent 901,197 described polyurethane, reaches the connecting substance their optimal physical properties in a relatively short time. The curing of the polyurethane compound with according to the method according to the invention takes only 15 minutes at + 15O ° C, so that the time required to such Establish connection is significantly shortened.

The use of an active hydrogen-containing compound with high reactivity also has the advantage of that the relatively low intermediate reaction of a polyurethane prepolymer or a simple polyisocyanate, with water, which can lead to foaming, hardly matters. This enables a very effective connection to be achieved without drying the tape or fabric prior to splicing, unless the fabric is near enough saturated with water. This further reduces the time required to establish a connection.

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The method according to the invention is particularly advantageous when the ends of the textile tape to be joined together or fabric interlocking contours, through which the contact surface for the connection bringing about Substance is at least twice as large, but preferably many times larger than the simple cross-sectional area of the ends of the tape to be joined. Preferably the configuration has a complementary array of V-shaped Notches across the entire width of each end of the tape, the notches being arranged so that when the ends are joined together each of which interlocks with one notch. The method of the invention for joining tape ends is as follows also described on the basis of V-shaped notches.

The depth of each notch, seen in the longitudinal direction of the tape or fabric, should be considerably greater than its width, to achieve a visual effect. The length and width of the notches can vary in size, but should Ratio of notch length to notch width are within the range 2: 1 to 30: 1 and preferably 2: 1 to 20: 1. The designation V-shaped notches also applies to modifications of notches, for example if the tips are rounded or are rectangular, provided that the edges to be connected between the notches are longer than the width and that the notches run essentially in the longitudinal direction of the tape or fabric. The connection can be improve if the V-shaped notches are slightly roughened with a suitable tool before notches and protrusions be joined together.

The liquid cast resin mixture can be applied to the connecting surfaces of the belt before they are joined together, and is then cured, but preferably the ends to be connected are assembled in an uncoated state, so that a narrow gap remains between the interlocking parts. This gap becomes with the liquid

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Filled with a casting resin mixture, which then cures under the action of heat and thereby results in the polyurethane compound.

According to a preferred embodiment of the invention, the liquid casting resin mixture consists of a methylenedianiline sodium chloride complex, which is dispersed in equal parts by weight of dioctyl phthalate, together with a polyurethane prepolymer, which is formed by the reaction between polytetramethylene ether glycol and a molar excess of tolylene diisocyanate and a reactive isocyanate content of 5 x 3 to 5.7 percent by weight results in, approximately, after application to the ends of the tape is 15 minutes cured at about 15O ⁰ C heat and an elastomeric polyurethane compound obtained whose degree of hardness is on the order of Shore ¹ a ¹ 90 °.

To give the surface a good finish at the junction a thin layer of a pourable liquid mixture that, when cured, results in a polyurethane, and this can, for example, be the same as for the connection itself, for example by painting, on the top and bottom of the tape are applied in the area of the connection point before curing takes place, and then cured at the same time will. A layer of coarse-meshed fabric or gauze can be used at the junction on the top and bottom can be applied as additional reinforcement. The liquid mixture is poured over the textile layer and passed through Cured by exposure to heat. The textile layer should preferably consist of synthetic yarn, for example polyamide yarn.

For carrying out the method according to the invention, the notched ends of the tape or fabric are preferred on a suitable pad or support so that the notched ends and that between them

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liquid cast resin mixture are supported by a flat sheet metal. The sheet metal can have a paint with a liquid pourable mixture, of which at least one component is blocked in its chemical reaction and which hardens when heated and results in a polyurethane connection, namely before the ends to be connected are applied, so that a continuous connection point at the finished connection point Surface arises. If the liquid putty is placed in a space between the notched ends, the space should be approximately 31175 n * ¹¹¹ (1/8 "). Once the liquid putty is between the interlocking notched ends, the entire joint is covered with another flat sheet Covered, which can be coated in the same way as described above.A suitable release agent must also be applied to the two sheets, for example a silicone for sheet metal.If necessary, the shell reinforcement can also be applied between the sheet and the top of the tape.

The joint is then cured by heat, which removes the active hydrogen present in the joint initially was chemically blocked, is released by, for example, placing the joint in an oven, or, if this does not work, insert the connection point between two heating plates of a press or a similar machine, where appropriate, a slight pressure can also be exerted on the connection point.

Before the casting compound is applied to the connection point, various additives can be added to it in different proportions will. These additives can be fillers, pigments, flame retardants (flame retardants), plasticizers and / or stabilizers which can be added either individually or in suitable combinations. A flame retardant substance should be added, for example, if polyurethane

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according to the invention, for example for connecting conveyor belts is used in coal mining, where metallic connectors have been used so far.

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Claims (1)

Claims 1. Process for connecting textile belts, conveyor belts, fabrics, etc. with the aid of a polyurethane connection, in which the ends of the Band or fabric parts are coated with a liquid casting resin mixture at around tree temperature, after which the casting resin mixture hardens by the action of heat and thus results in the polyurethane connection characterized in that in the casting resin mixture at least one component in its chemical The reaction is blocked in such a way that the casting resin mixture does not harden at tree temperature, and that the hardening by the action of heat at the ends that are connected to one another only at a temperature above the tree temperature begins after the two ends have been butted together. 2. The method according to claim 1, characterized net that the liquid casting resin mixture on the ends of the tape or fabric is applied before they are butted together. 3 * Method according to claim 1 or 2, characterized in that the ends to be joined are each designed to interlock in a form-fitting manner 709836/0994 ORIGINAL INSPECTED -ir- that the contact surfaces of the ends provided with the casting resin mixture are at least twice as large what is the smallest cross section at the ends of the tape or fabric. 4. Process for connecting textile straps, fabrics inter alia with the aid of a polyurethane connection, in particular according to claim 1, characterized in that the two to be connected to one another Tape or fabric ends are provided over their entire width with form-fitting, preferably V-shaped notches, and that the notched ends are pushed together in such a way that a narrow gap remains between the notches liquid casting resin mixture is filled at room temperature, which hardens to a polyurethane compound by the action of heat, and that the casting resin mixture at least has a component which is blocked in its chemical reaction in such a way that at tree temperature no hardening of the casting resin mixture occurs, and that the casting resin mixture in the gap for connecting the Ends is hardened by the action of heat at a temperature above the tree temperature. 5. The method according to claim 4-, characterized in that the ratio of length to width of each Notch ranges from 2: 1 to 3Os1, inclusive. 6. The method according to claim 4 or 5 »characterized in that the edges of the preferably V-shaped notches of the tape or fabric ends with a suitable tool before the form-fitting assembly be roughened. 7. The method according to the preceding claims, characterized characterized that the liquid Giefiharz- 709836/0994 -'tr- mixture of a polyisocyanate or polyurethane prepolymer which contains a polyisocyanate reactant and a polyactive hydrogen containing Compound in which the active hydrogen groups are chemically blocked at tree temperature. 8. The method according to claim 7 »characterized in that that the polyisocyanate of the group 2,4-tolylene diisocyanate, m-phenylene diisocyanate, 1,5 naphthalene diisocyanate or triphenylxiethane triisocyanate. 9 «Method Lach claims 7 or 8, characterized in that the polyactive hydrogen containing Compound a complex of methylenedianiline and contains sodium chloride. 10. The method according to claim 9 »characterized in that the liquid casting resin ^{mixture is cured at a temperature of about + 150 0} C over a period of about 15 minutes. 11. The method according to one or more of claims 7 to 10, characterized in that the casting resin mixture proportionally different additives, for example fillers, pigments, flame retardants, plasticizers and / or stabilizers are added. 12. The method according to any one of the preceding claims, characterized in that in the area of the to be joined Put a thin layer of the liquid casting resin mixture on the surface of the tape or fabric is applied before the cast resin mixture located on the tape or fabric is cured under the action of heat. 13 · The method according to claim 12, characterized in that on the surface of the ends to be connected • as 709836/0994 - 4 - -Hf - of the tape or fabric for reinforcement purposes coarse-meshed fabric or gauze is applied that is held by the hardening of the liquid cast resin mixture at the connection point. 14. Textile belt, conveyor belt, fabric, etc. with one after one or more of the preceding claims produced connection point. 709836 / 099A - 5 -