DE1964834A1 - Polyurethane elastomers mfr by direct reac - tion in extruder - Google Patents

Abstract

Elastomers are produced by extruding diisocyanates, poly-OH cpds. or mol. wt. 800-3500, glycols of mol. wt. is not >300, opt. triols of mol. wt. is not >500 and release agent, reaction being carried out at 90-220 degrees C. in multi-screw extruder, opt. with simultaneous moulding. These elastomers can be used for machine parts e.g. cog. wheels, sockets, cable covering, hose, sealants and bushes. Process gives considerable saving in heating, since casting to sheet, granulation and subsequent hot moulding are eliminated.

Description

Process for the production of polyurethane elastomers Elastic Plastics based on polyisocyanates, polyhydroxyl compounds and optionally chain extenders are known. Such plastics will be in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl Hanser-Verlag, in detail described. Many of these polyurethane elastomers can be deformed afterwards be brought into the final form. For example, by injection molding or molded parts are produced by extrusion. Other methods of making Molded parts are the pouring of the reaction components into molds or the pressing of rollable polyurethane elastomers. For the continuous production of panels, Foils, hoses, cable jackets and profiles, however, come first and foremost from extrusion of thermoplastic polyurethane elastomers. Such tilermoplastic Polyurethane elastomers are obtained by adding polyester or polyether diols and glycols, e.g. B. Idutanediol-1,4, with approximately stoichiometric amounts of diisocyanates implements.

This implementation must be carried out in compliance with exact reaction conditions be performed. Devices for carrying out the reaction are, for. Am the German Auslegeschrift 1 141 772 described. After that, the well-mixed and precisely dosed reaction partners are brought into a preheated liquid bath and in this brought to e-reaction, then cleaned, granulated, and first After these process steps, the extrusion into finished molded parts can take place.

According to the American patent 1 750 018, the reaction components, Polyester, butanediol and polyisocyanate, fed to a mixing head via metering pumps. From this mixing head, the components are transferred to a conveyor belt Polytetrafluoroethylene brought and passed through an oven at temperatures is heated to 100 ° C. After several minutes, the material is cut into strips and then tempered for a further 24 hours at 100 ° C. under nitrogen. Only after During this time processing on injection molding or extrusion machines can take place.

According to the German Ausle; font 1 106 969 are thermoplastic Polyurethane elastomers are obtained by adding the stoichiometrically dosed starting components, Polyester, 1,4-butanediol and isocyanate, stirred for one minute, to react and then pour into larger containers, screw these containers and 3.5 hours heated in an oven to 140 ° C. After cooling, it is granulated and then processed by extrusion. According to the German Auslegeschrift 1 165 852 Thermoplastically deformable polyurethane elastomers can also be produced by the reaction components are mixed at temperatures between 60 and 175ob and the reaction mixture to solidify it is poured onto heated metal sheets coated with release agents. The reacting liquid is distributed in good time to allow it to detach from the base to facilitate. The storable thermoplastic polyurethane wet that is preserved in this way must be comminuted by cutting, chopping and grinding and even eating subjected to shaping processing by injection molding, extrusion or pressing will.

The conventional methods are based on processing Polyurethane granules. The granules required for this are complicated Processes.

The present invention relates to a method of production of polyurethane elastomers by extrusion from diisocyanates, polyhydroxyl compounds with a molecular weight of 800 to 3500 and glycols with a molecular weight of up to 300, optionally with the use of triols with a molecular weight of up to 500, in the presence of lubricants, which is characterized in that the reaction the components at temperatures between 90 and 220 ° C in a multi-screw extruder, optionally with simultaneous shaping.

According to the invention, it is possible while maintaining the specified temperature conditions to direct the reaction so that a homogeneous mass is obtained and at the same time shaping can take place. The exothermic reaction that occurs during the reaction a melting of the polyurethane elastomers. Considerable amounts of heat are therefore saved. Pouring the reaction components and the like onto metal sheets, granulating and the like additional heat input during shaping is not required with this new process more required.

As starting materials for carrying out the process according to the invention Polyhydroxyl compounds with a molecular weight of 800 to 3500 are known Type in question, e.g. B. the per se known hydroxyl groups containing polyesters, Polyethers, polythioethers, polyester amides, polyacetals or polycarbonates, as polyether polyols Particularly suitable are, for example, adducts of ethylene oxide or propylene oxide with starter molecules such as water, glycol, i, 2-propanediol, 1,3-propanediol, glycerol, trimethylolpropane or amines such as NH3, ethylenediamine, butylene glycol polyethers are also suitable mixed polyethers which, in addition to the components mentioned, contain other glycol residues, such as B. Phenylethylene glycol residues included. Dihydroxy polyethers are preferred used. But it can also mixtures of dihydroxy polyethers can be installed with multifunctional polyethers.

As a HYdroxvDolvester. which have presumably drimeric hydroxyl rupees 4 -pen / take e. B. Polyester in question, as they are from dicarboxylic acids such as succinic acid, Adipic acid, cyclohexanedicarboxylic acid, terephthalic acid and diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol were obtained can be. Polyesters containing two hydroxyl groups are preferably used, however, mixtures of bifunctional polyesters with multifunctional ones can also be used Polyesters are used. r, aliphatic having terminal hydroxyl groups Polycarbonates are also suitable for the process according to the invention. Be here in particular 1,4-butanediol polycarbonate and 1,6-hexanediol polycarbonate, the z. B. can be produced by reacting these glycols with diphenyl carbonate. According to Mixtures of any desired polyhydroxyl compounds can be used in the procedure according to the invention be used, e.g. B. Mixtures of polycarbonates with polyesters or mixtures of polyethers, polycarbonates and polyacetals.

According to the invention, any desired, conventional diisocyanates can be used as diisocyanates Type in question, e.g. E.g .: 2,4-tolylene diisocyanate and / or its mixtures with 2,6-tolylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 4,4'-diisocyanatodiphenylmethane and its mixtures with 2,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatodiphenylpropane, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 3,3'-dimethoxy-4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatodiphenyl, 1,5-diisocyanatonaphthalene.

As examples of low molecular weight glycols with a molecular weight up to 300 are ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, hydroquinone bis-hydroxyethyl ether, diethylene glycol, triethylene glycol called.

These crosslinking agents preferably have primary OH groups. Optionally, triols such as trimethylolpropane, glycerol or hexanetriol- (1,2,6) are also used, which usually have molecular weights of up to 500.

When carrying out the method according to the invention are in the Usually about stoichiometric ratios between the NCO groups and the existing ones OH groups complied with.

In general, the NCO to OH ratio will be between 0.97 and 1.10 lie. Slight deviations from this ratio are of course possible.

The inventive method is carried out in the presence of lubricants, This causes the reaction mixture to stick to the screw and walls in the multi-screw extruder decrease, performed.

These are lubricants or release agents known per se So are for the process z. B. natural and synthetic derivatives of fatty acids useful. Amides of C-C20 monocarboxylic acids such as dodecylamide, Decylamide, oleylamide, stearoylamide in amounts of about 0.3 to 5%. Also very much The diamides from aliphatic monocarboxylic acids with more than 9 are well suited C atoms and aromatic or aliphatic diamines, such as. B. phenylene-bis-pamitamide, Ethylene-bis-stearylamide. As examples, esters of fatty acids, e.g. B. with more than 10 carbon atoms, such as methyl palmitate, butyl stearate and glycerides of carboxylic acids with more than 8 carbon atoms. Also polyethylene waxes and synthetic waxes, montan waxes and their mixtures can be used. The lubricant used according to the invention is preferably 0.3 to 5% by weight of Derivatives of fatty acids with more than 12 carbon atoms, e.g. B.

Esters or amides of the fatty acids.

The reaction can be carried out from these starting materials in a conventional manner after a one-step process or after a two-step process, if necessary also carried out in the presence of known activators, such as tin compounds or amines will. After the one-step process, all of the reactants are mixed and put in the multi-screw extruder reacted, while according to the two-stage process initially from monomeric isocyanates under polyhydroxyl compounds of molecular weight 800 to 3500 a pre-adduct containing isocyanate groups is formed. The two-step process is preferably used in the method according to the invention. A special Embodiment of the process is that the reaction in the presence of organic inert solvents, e.g. B. in the presence of esters, ethers, ketones, Hydrocarbons, halogenated hydrocarbons, is carried out. Eligible Solvents are e.g. B. butyl acetate, methyl ethyl ketone, chlorobenzene, decalin, Acetone. The reaction components used are metered in z. B. via gear or piston pumps in a known manner, as well as the mixing the reactant.

The mixed reactants are fed into a multi-screw extruder brought in. The multi-screw extruder to be used according to the invention is per se known and commercially available.

Suitable are e.g. B. twin screw extruder, preferably if they be heated by liquid or by steam. But also come according to the invention Extruders in question that have more than two screws, e.g. B. three or four screw extruders. The dwell time in these extrusion machines depends on the hardness of the material to be produced Product. In general, residence times in the extruder are from 1 to 5 minutes Temperatures between 100 and 1900C required. Hard polyurethane elastomers with a Shore hardness between 90 and 98 A are generally with residence times of 1 to 2 minutes can be fabricated, while soft products, Shore A = 70 to 85, may require dwell times of 4 to 8 minutes. To the geometry of the Snails in these Extrusion lines are not special requirements to deliver. It is particularly advantageous to use a helical thread more uniformly Aisle depth in the feed zone, d. H. that is, in the area of liquid reaction components apply, then provide a decompression or degassing zone. At this degassing zone is advantageously followed by a compression zone. At the end The forming tool is attached to the extruder. As such tools can z. B. slot nozzles, hole nozzles, profile form nozzles, hose form nozzles or cable sheathing heads can be connected in a conventional manner. Those emerging from the extrusion molds Polyurethanes can in a manner known per se by means of cooling rolls, cooling baths or be cooled by tuft. The process products normally do not require any additional post-treatment, as they are after the new process with no tolerances the residence time with very precise temperature control with exclusion of moisture getting produced. They therefore have a high degree of strength and properties on. The products of the process can subsequently undergo thermoplastic deformation be subjected, for example, by deep-drawing the films, plates or strands or blow. But you can also shredded and a subsequent thermoplastic Processing on injection molding or extrusion machines if for the production of elastomers mainly linear bifunctional starting materials be used.

This makes it possible to collect waste from manufacturing, such as B.

Punching waste, further processing and reuse.

The process products are used in many ways, e.g. as machine elements, such as gears, bushings, cable jackets, hoses, seals and bearing shells. the Possible uses of the process products are known per se. example 1: A mixture of 100 parts by weight of a polyester of adipic acid became and 1,4-butanediol of OH number 51.65, 9.5 parts by weight 1,4-butanediol, 1.6 parts by weight Oleylamide and 1 part by weight of a 2,2'-6,6'-tetraisopropyldiphenyloarbodiimide manufactured. This polyol mixture was heated to 120 ° C. and by means of gear pumps fed to a mixing nozzle.

A second gear pump was used to melt the same mixing head 4,4'-Diisocyanatodiphenylmethane metered in.

120 g of the polyol mixture with 42 g of the diisocyanate were used per unit of time mixed. - ie the low-viscosity mixture emerging from the mixing device is ri Temperaturvai100-110Q and runs directly into a twin-screw extruder, which opens with steam from the outside 150 to 15400 is heated. In the reacting polyurethane composition, the following were found Temperatures measured: Feed zone: 160 to 16500 Screw center: 170 to 1800C Material temperature when leaving the extruder: 19500 At the end of the extruder occurs the hot, molten polyurethane through a round opening. It becomes a strand peeled off 5 mm in diameter and cooled by cold air.

The cord thus obtained was wound by a mechanical winder deducted evenly. In a parallel experiment, a slot nozzle from 100 mm wide and 3 mm thick used. The one extruded through this die head The tape was smoothed by means of cooling rollers and reduced to a thickness of 2.5 mm. The test values are given in the table. The second column of the table shows the test values after granulation of the tape and processing of this granulate Injection molding machines.

The twin screw extruder used in these experiments had one Length of 1200 mm, the screw diameter was 30 mm. the Power consumption during the extrusion of the reacting components was 1.5 kW each Hour. The power consumption fluctuated insignificantly than the amount of 4.3 kg per hour was increased to 7.7 and in a further experiment to 10 kg per hour. In the Processing of finished granules the power consumption was 2.2 kW per hour when 5.9 kg of the granules were processed.

Table Dimension DIN I II Tensile strength kp / cm2 53 504 498 492 Elongation at break % 53504 578 622 Tear strength kp / cm 53515 73 75 Shore hardness ° A 53505 85 86 Elasticity% 53512 48 48 Abrasion mm 53516 25 27 Example 2: Those used in Example 1 Liec'iktionsverbindungen were in the presence of 40% methyl glycol acetate in the extruder implemented. A twin screw extruder was used, which was operated with steam from the outside was heated by 5 atü. The snails were on one length in the heating zone of 600 mm equipped with a uniform thread. This was followed by 200 mm degassing zone and a compression zone of 400 mm (progressive, with compression 3: 2). The degassing zone was connected to a cooling system to prevent the distilling off Collect solvent. At the head of the extruder was made by means of a slot die the material is taken and fed to the rolls of a melt calender, Zimmer system. The polyurethane melt was transferred to a textile and this cotton fabric with an even layer of polyurethane elastomer. In further attempts a release paper was used instead of the textile. The films thus obtained could be deformed by deep drawing. In the tensile test according to DIN 53504, these Film tensile strengths 500 to 520 kp / cm² and an elongation at break of 620 aXo measured. The films obtained are transparent.

Example 3: In a stirred tank, a pre-adduct was made from 950 parts by weight of a linear polypropylene glycol ether with an OH number of 56, made from propylene oxide and 1,4-butanediol, 50 parts by weight of a trifunctional polypropylene glycol ether with an OH number of 56.2, produced by reacting propylene oxide and trimethylolpropane, and 15 parts by weight of stearylamide, 15 parts by weight of 2,2'-6,6'-tetraisopropyldiphenylcarbodiimide and 1700 parts by weight of 4,4'-diisocyanatodiphenylmethane prepared by adding the mixture was heated to 950C for half an hour. In a second stirred tank was a Diol mixture of 1000 parts by weight of a polyester al1s adipic acid and ethanediol (OH number 56.1), 500 parts by weight of 1,4-butanediol and 20 parts by weight of a carbon black and 20 parts by weight of methyl stearate. The pre-adduct was with a Temperature of 950C, the polyol mixture with a temperature of 700C by gear pumps fed to a mixing head. The reacting mixture flows out of this mixing device directly into the extruder described in Example 1. The extruder was on the outside with Steam heated to 14400. Every hour, 6160 g of the pre-adduct and 3440 g of the diol mixture were added fed to the mixing unit. Accordingly, the output of the extruder was 9.6 kg per hour. The mean residence time in the extruder was 2.5 minutes. In the crowd a temperature of 184 ° C. was measured in the middle of the extruder, the melt temperature at the exit of the extruder was 21,900. There were several Tools attached and extruded U-profiles and strips.

The tapes, after granulation, could be injection molded into new molded articles are processed. The following test values were measured on the elastomers: Tensile strength: 324 kp / cm² Elongation at break: 312% Tear strength: 97 kp / cm Abrasion: 42 mm3 Shore hardness A: 95 Shore hardness D: 50

Claims (5)

Claims: Process for the production of polyurethane elastomers by extrusion from diisocyanates, polyhydroxyl compounds of molecular weight 800 to 3500 and glycols with a molecular weight of up to 300, optionally below Use of triplets with a molecular weight of up to 500, in the presence of lubricants, characterized in that the reaction of the components at temperatures between 90 and 220 ° C in a multi-screw extruder, optionally with simultaneous Shaping, is carried out. 2) Method according to claim 1, characterized in that as Lubricant 0.3 to 5% by weight of derivatives of fatty acids with more than 12 carbon atoms used. 3) Method according to claim 1, characterized in that as Diisocyanates Pre-adducts containing isocyanate groups, prepared from monomeric Diisocyanates and polyhydroxyl compounds with a molecular weight of 800 to 3500 are used. 4) Method according to claim 1, 2 or 3, characterized in that the reaction is carried out in the presence of organic, inert solvents. 5) Method according to claim 1, 2, 3 or 4, characterized in that that the process products are subsequently subjected to thermoplastic deformation.