DD262237A1 - METHOD FOR PRODUCING A THERMOPLASTICALLY PROCESSABLE POLYURETHANE GRANULATE - Google Patents

Abstract

The process for producing a melt-processable polyurethane granulate relates to the conversion of optionally foamed polyurethane elastomer wastes or -ausschussteilen based on polyester alcohols to a relatively feinkoernigen, free-flowing granules. The polyurethane elastomer waste may contain solid built-in parts, for example of wood, metal and / or plastic. The aim of the invention is the development of a process for the processing of polyurethane elastomer wastes without great energy consumption in a technologically simple manner. According to the inventive method, the polyurethane elastomer wastes are optionally dissolved under elevated pressure at about 90C in dimethylformamide. This solution is diluted with a solvent which strongly swells but does not dissolve the polyurethane elastomers used. From this diluted solution, the elastomer is separated and dried by mixing the polymer solution with a solvent which does not cause the elastomer to swell or only slightly swells. You get a feinkoerniges, free-flowing product that is processed on ordinary thermoplastic machines.

Description

Field of application of the invention

The process for producing a melt-processable polyurethane granulate relates to the conversion of optionally foamed PUR elastomer waste into a granulate which can be processed on conventional Thermaplast processing machines. The PUR elastomer waste to be processed may contain solid constituents, for example wood, metal and / or plastic components.

Characteristic of the known technical solutions

In the production of moldings from foamed PUR elastomers incurred inevitably Committee moldings, their use and recycling is problematic to a usable product. According to the known methods, the reject parts or waste of polyurethane elastomers must be comminuted by a work-up. Thereafter, the blowing agent is to be removed, either by storage for months at room temperature or at least 60 hours at 80 ° C to 100 ⁰ C. Only then can the splinter granules be fed to the actual processing. (DD-WP 115067 and DD-

Disadvantages of this type of treatment, which is primarily suitable for shoe soles, are the need to mechanically disintegrate, melt, degas and granulate the moldings by high energy expenditure and with costly equipment.

According to the known methods, it is not possible to work up moldings which contain built-in parts of wood, metal and / or plastics.

Object of the invention

The aim of the invention is to develop a method which makes it possible, without great technical effort and in a simple, energy-saving manner foamed PUR-Elastomerabfälle that may contain built-in parts of wood, metal and / or plastics in a processable on conventional thermoplastic processing machines To transfer granules.

Explanation of the essence of the invention

The invention has for its object to provide a method for producing a melt-processable PUR granules are used in the waste and rejects from possibly foamed PUR elastomers based on polyester alcohols, the method is not very energy-consuming and technologically simple shall be.

According to the invention the object is achieved in that the resulting in the production of PUR elastomer molded parts based on polyester PUR elastomers waste and rejects under any elevated pressure at about 90 ⁰ C in dimethylformamide (DMF) are solved. This solution is diluted with a solvent which strongly swells but does not dissolve the PU elastomers used. From this dilute solution, the polymer is precipitated by mixing the polymer solution with a solvent which does not or only slightly swells the polymer. As a solvent, the polyurethane elastomers strongly swell, but not solve, z. As methylene chloride, cyclohexanone, esters of acetic acid containing less than 6 carbon atoms mono- or dialcohols, aliphatic ketones with not more than 9 carbon atoms suitable.

As solvents which do not or only slightly swell polyurethane elastomers, e.g. Alcohols having not more than 12 C-atoms, preferably methanol, hydrocarbons and hydrocarbon mixtures having a boiling point below 160 ° C suitable.

The precipitated polymer is separated in a suitable and known manner from the liquid phase and dried with hot air. This gives a fine-grained, free-flowing product, which can be processed in this form on conventional thermoplastic processing machines.

After dissolution of the elastomeric parts in DMF, foreign bodies such as built-in components of wood, metal and / or plastics can be separated in a known manner before or after mixing the solution with the solvent which swells the polymer but does not dissolve it.

The inventive method has the advantage that moldings and waste from possibly foamed polyester PUR elastomers are converted into a thermoplastically processable polyurethane granules without mechanical action in relatively inexpensive mixing and dissolving containers. Energy-intensive mechanical comminution processes are dispensed with, as is the energy-intensive melt granulation on costly vented extruders. With the method according to the invention, it is also possible to work up PU elastomer waste containing built-in parts made of wood, metal and / or plastic.

The granules produced by the process of the invention is a relatively fine-grained, free-flowing product that can be easily processed on conventional thermoplastic processing machines by injection molding or extrusion to form parts and profiles.

A further advantage is that the solvents used can be recovered and recycled to the process.

The invention will be explained in more detail below on some embodiments.

Embodiment 1

2 kg of shoe soles made of a polyurethane system consisting of polyester polyol, chain extender and diphenylmethane diisocyanate (MDI) are dissolved at 80 ° C to 90 ⁰ C in 8kg of DMF under atmospheric pressure, filtered and cooled to room temperature.

The clear solution is added with stirring with 30 kg of methylene chloride. With the rapid addition of 100 kg of methanol, a relatively fine-grained precipitate is obtained, which is separated by suction from the solvent mixture and dried at 70 ⁰ C. The result is a relatively fine-grained, free-flowing granules with a bulk density of 0.15 kg / l.

Embodiment 2

10 kg of a solution of the elastomer in DMF according to Example 1 are mixed with 30 kg of acetone. The clear solution is added with stirring with 75 kg of anhydrous ethanol and thereby precipitated the polymer. The precipitate is separated from the liquid phase and dried at 80 ⁰ C. The result is a relatively fine-grained, free-flowing granules with a bulk density of 0.15 kg / l.

Embodiment 3

10 kg of a solution of the elastomer in DMF according to Example 1 are mixed with 30 kg of ethyl acetate. The clear solution is added with stirring 5 kg of petroleum ether with a boiling range of 50 ⁰ C to 80 ⁰ C and thereby precipitated the polymer. The precipitate is separated from the liquid phase and dried at 8O ⁰ C. The result is a relatively fine-grained, free-flowing granules with a bulk density of 0.15 kg / l.

Embodiment 4

The granules obtained according to Example 1 or 2 or 3 are processed in an extruder at 170 ⁰ C to a round strand of 2 mm diameter.

The strand obtained has the following physical-mechanical properties:

Tensile strength MPa 53.7

Breaking strain% 1100

Tensile Modulus at 100% Elongation MPA 9.8

Permanent elongation at 100% 6.0

Permanent elongation at 300% 16.0

Embodiment 5

Dyes obtained according to Example 1 or 2 or 3 are sprayed into test pieces in an injection molding machine under the following conditions:

Temperature zone 1: 130 ⁰ C 19.9 Temperature zone 2: 145 ° C 550.0 Temperature zone 3: 160 ⁰ C 686.0 Mold temperature: 23 X 44.0 Hold time: 120s 82.0 injection time 20s 25.0 injection pressure 46.0 MPa backpressure 10,0MPa The following physical mec Tensile strength MPa Breaking elongation% Tear strength N / cm Abrasion mm ³ Hardness Shore A Impact resilience%

Claims (6)

1. A process for the preparation of a melt-processable polyurethane granules by conversion of optionally foamed polyurethane elastomer waste or rejects based on polyester alcohols containing built-in parts such as wood, metal and / or plastics, characterized in that the polyurethane elastomer waste or rejects parts if necessary be dissolved under elevated pressure at about 90 ° C in dimethylformamide and then the solution with a solvent that swells the polyurethane elastomers strong swell, but does not dissolve, and then diluted with a solvent that does not or only slightly, the polyurethane elastomers swelled, precipitated, separated and dried. 2. The method according to item 1, characterized in that as solvent, which can swell the polyurethane elastomers used strong, but not solve, z. As methylene chloride, cyclohexanone, esters or acetic acid containing less than 6 carbon atoms mono- or dialcohols, aliphatic ketones are used with not more than 9 carbon atoms. 3. The method according to item 1, characterized in that are used as solvents which do not or only slightly swell the polyurethane elastomers, alcohols having not more than 12 C-atoms, preferably methanol, hydrocarbons and hydrocarbon mixtures having a boiling point below 160 ⁰ C. , 4. The method according to item 1 to 3, characterized in that before or after the mixing of the polyurethane elastomer solution with the solvent that the polyurethane elastomers can swell strongly, but does not dissolve foreign bodies, such as built-in parts of wood, metal and / or plastic are separated in a known manner. 5. The method according to item 1 to 4, characterized in that the fine-grained, free-flowing polyurethane granules obtained after drying is easily processed on conventional thermoplastic processing machines by injection molding or extrusion. 6. The method according to item 1 to 3, characterized in that the solvents used are worked up by known methods and reused.