WO2010020233A1

WO2010020233A1 - Plastics production method

Info

Publication number: WO2010020233A1
Application number: PCT/DE2009/001164
Authority: WO
Inventors: Rolf Galle-Gutbrecht; Renate Brielmann
Original assignee: Trelleborg Sealing Solutions Germany Gmbh
Priority date: 2008-08-20
Filing date: 2009-08-19
Publication date: 2010-02-25
Also published as: DE102008038499A1

Abstract

The invention relates to a method for producing a plastic material from a polymer containing carbon nanotubes, said method comprising the following steps: a polymerisation reactor is filled with at least one polyol and a diisocyanate for producing a prepolymer; the prepolymer is mixed with a chain extender in order to transform the prepolymer into the polymer in liquid form; and the polymer is transformed or cooled to form the solidified plastic material. The carbon nanotubes are added to the prepolymer and/or the polyol before and/or during the mixing of the prepolymer with the chain extender.

Description

Plastic manufacturing process

The invention relates to a method for producing a plastic (plastic production method) from a carbon nanotube-containing polymer with the method steps:

Filling a polymerization reactor with at least one polyol and a diisocyanate to produce a prepolymer, mixing the prepolymer with a chain extender to convert the prepolymer into the polymer in liquid form, and

- Transfer or cooling of the polymer to solidify the plastic. With such methods, for example, thermoplastics made of polyurethane (PU), ie thermoplastic polyurethane elastomer (TPU) produced.

The plastic is then in the form of granules for

Further processing, i. for molding plastic parts, e.g. using an injection molding process, used as an intermediate. For example, To achieve an electrical conductivity of the plastic carbon nanotubes, so-called CNTs (Carbon IMano Tubes), to introduce into the plastic, the plastic granules are melted and in an extruder, e.g. a twin-screw extruder, with the carbon nanotubes added. There is a risk of overheating of the plastic in the extruder. The thus obtained carbon nanotube-containing plastic is solidified again by cooling and used again in the form of granules for further processing as an intermediate. For final shaping, therefore, further melting takes place, for example by To mold plastic parts by injection molding.

When a molten plastic is a relatively viscous liquid, whereby a uniform distribution of carbon nanotubes in the plastic by mixing in the extruder is only possible to a limited extent. The repeated melting processes until final shaping lead to quality losses in the plastic itself and in particular in terms of the properties of the

Carbon nanotubes. It can also come when remelting the carbon nanotube-containing plastic to demixing. From DE 10 2004 010 455 A1, a process is known in which carbon nanotubes are added to one of the raw materials in the production of plastics, for example the polyol component, for producing an electrically conductive plastic. Electroconductive plastics are plastics whose electrical conductivity is less than ten thousand ohm-cm. For this purpose, the CNTs are mixed in an amount of more than one percent by weight. When mixing the carbon nanotubes into the polyol component, however, an uneven and insufficient distribution of the carbon nanotubes in the finished plastic can occur, since the carbon nanotubes are agglomerated and / or tend to form agglomerations.

It is also known from US 2002/0137871 A1 and DE 103 92 469 to add carbon nanotubes to a liquid polyol component. In the US 2002/0137871 Al while the

Plastic manufacturing components mixed and used immediately afterwards as a spray. In DE 103 92 469 electrically conductive plastic foams are produced. The mixing of the carbon nanotubes is supported by the foaming process.

DE 10 2006 037 582 A1 also proposes processes for the preparation of electrically conductive polyurethanes which are not foamed, but solid, wherein the carbon nanotubes, for example, into a Polyol component are mixed. However, non-pumpable polyol dispersions are produced which are difficult to process.

The plastics produced by the known processes are only of limited suitability for use as sealing and / or damping material, i. For example, for the production of seals, in particular high pressure seals in hydraulic applications. Plastics used as sealing and / or damping material are compact, i. not foamed and not electrically conductive, i. they have an electrical conductivity of more than ten thousand ohm-cm. For use as a compact sealing and / or damping material, a very uniform distribution of the carbon nanotubes in the plastic without foaming of the plastic is necessary, as otherwise the sealing and / or damping material is e.g. unevenly worn and cause malfunction e.g. of seals made therefrom tends.

The invention has for its object to provide a method for producing a, in particular compact and electrically non-conductive,

To provide plastic from a polymer containing carbon nanotubes, which avoids the disadvantages of the prior art, in particular, a very uniform distribution of carbon nanotubes in the plastic to be achieved. This object is achieved by the method steps listed in the claims. The dependent claims represent preferred embodiments of the invention.

In the method according to the invention for producing a polymer, in particular a compact and electrically non-conductive plastic, comprising a carbon nanotube-containing polymer, the following method steps are carried out:

Filling a polymerization reactor with at least one polyol and a diisocyanate, e.g. MDI (methane diisocyanate), TDI (toluene

Diisocyanate), TODI, NDI, PPDI or CHDI to produce a prepolymer, i. a polyurethane prepolymer,

Mixing the prepolymer with a chain extender to transfer the prepolymer into the polymer in liquid form, and transferring the polymer to form the solidified plastic.

Before mixing the prepolymer with a chain extender, for example 1.4 BDO (dihydroxybutane or butanediol) or HQEE (hydroquinone di (beta) ether), the prepolymer from the polymerization reactor can be transferred to a suitable vessel for mixing. In order to ensure a thermoplastic processability of the plastic produced is used as chain extenders a linear (bifunctional) and / or at least in certain proportions a trifunctional crosslinker (eg 1.1.1-trimethylolpropane) chain extender. The carbon nanotubes may be added to the polymerization reactor and / or to the latter vessel. Under the vessel into which the prepolymer is transferred can also be a mixing head, in particular a Casting machine, for metered mixing of the prepolymer with the

Chain extenders are understood.

The carbon nanotubes are mixed before mixing

Prepolymer having the chain extender added to the prepolymer and / or the polyol, i. brought in. The addition of the

Carbon nanotubes can also be made by charging a polyol into the polymerization reactor in which already

Carbon nanotubes are dispersed.

According to the invention, the polyol is degassed before adding the diisocyanate and / or the prepolymer before mixing with the chain extender, wherein the degassing after adding the

Carbon nanotubes is made, and to assist the degassing, a gas suction is performed to generate a negative pressure.

With the method according to the invention, a solidified, rubber-elastic sealing and / or damping material can be produced as the plastic. That The plastic is not foamed but solid, so that in particular seals can be made.

The carbon nanotubes are thus introduced into the liquid phase of the polymerization process, ie the polyol and / or the prepolymer are each in their liquid phase when adding the carbon nanotubes. In this case, no solvents must be used. Polyols can have different melting points. There are polyols which can be used for the process according to the invention Room temperature are liquid, but also polyols which have a melting point of 20 to 120 degrees Celsius.

Useful diisocyanates are liquid at room temperature. For example, they have melting points between 21 degrees Celsius and 127 degrees Celsius, e.g. 38.5 degrees Celsius. The polyol is therefore, if it is not already liquid, tempered prior to mixing with the diisocyanate and / or the Kohienstoffnanoröhren to its melting. When mixed in the polymerization reactor so there is a temperature at which the polyol is melted. The mixing of the prepolymer with a preferably aromatic chain extender is preferably carried out at a temperature of at least 100 degrees Celsius, since the HQEE (aromatic chain extender), which is furthermore preferably used as a chain extender, is also melted at this temperature. To produce a non-conductive plastic, the

Kohanstoffnanoröhren in an amount of less than one percent of the weight of the finished plastic (weight percent) was added. Preferably 0.05 to 0.3 weight percent Kohienstoffnanoröhren be added, ie mixed. The inventive introduction of the Kohienstoffnanoröhren a very uniform distribution of Kohienstoffnanoröhren in the plastic can be achieved. Degassing at reduced pressure, ie, applying a vacuum, at a pressure of low atmospheric pressure, causes the formation of agglomerations of the Kohienstoffnanoröhren is avoided, or existing agglomerations are broken by the suction of located between the agglomerated Kohienstoffananothren gases. To assist the degassing, a gas suction for generating the negative pressure is carried out, that is, the degassing takes place after or during evacuation of the gas space above the reaction mixture. By evacuating the breakup of particle agglomerations of the carbon nanotubes and / or added additives and thus the distribution (dispersion quality) is supported. The degassing is preferably carried out during mixing of the carbon nanotubes with the liquid polyol and / or the liquid prepolymer for dispersing the carbon nanotubes in the liquid polyol and / or the liquid prepolymer.

A particularly uniform distribution of carbon nanotubes results when, after the addition of the carbon nanotubes, a stirring mixing of the carbon nanotubes with the polyol or the prepolymer, e.g. by means of a toothed disk, preferably in a vacuum, i. at an existing negative pressure, is performed. In the process, the carbon nanotubes disperse in the polyol or the prepolymer. That is, the singulation of the carbon nanotubes or the breaking up of present agglomerates is thereby assisted.

The process according to the invention is particularly suitable for producing a thermoplastic polyurethane elastomer (TPU) as the plastic. TPU is e.g. used as a polyurethane sealant.

In order to achieve an optimum viscosity of the polyol for mixing with the carbon nanotubes, the polyol can be added before adding the Diisocyanate be tempered. When degassing the polyol, side reactions are suppressed.

By adding at least one additive before degassing, e.g. a dye, in the polyol further desired properties of the plastic to be produced can be adjusted. The additive is preferably added prior to degassing to prevent gases introduced into the polyol, e.g. To remove air with.

The carbon nanotubes can also be added to the polyol before degassing in order to counteract the formation of gas inclusions by the addition.

Very advantageously, the transfer of the prepolymer is carried out in the liquid polymer in a Spritzgießcompounder. That the

Prepolymer is transferred before mixing with the chain extender from the polymerization in the Spritzgießcompounder. Injection molding of the liquid polymer may then be performed immediately after the completed polymerization without intermediate cooling and remelting. So it will be one for

Solidification of the polymer leading to cooling between the transfer of Prepoiymers in the liquid polymer and injection molding avoided.

Below are two examples of process steps of the inventive method for producing a plastic a carbon nanotube-containing polymer, namely PU with CNT.

Example 1:

1. filling the polymerization reactor with

• polyol (one or more)

• additives (optionally in specific order) • CNT (preferably pre-dried);

2. Start degassing, exact temperature control, e.g. to 100 degrees Celsius to liquefy the polyol, and dispersion of the CNTs and additives (e.g., dye, processing aids, friction modifiers, age reducers, etc.) in the polyol, e.g. by mixing by means of a rotating toothed disc;

3. adding diisocyanate, such as MDI (methane diisocyanate, in particular 4,4 ^'- diphenylmethane diisocyanate), preferably while monitoring the reaction profile, eg by reaction time, temperature, speed, torque of the pulley, etc .; during the reaction time, an exothermic prepolymer reaction takes place;

4. After the predefined reaction time of e.g. About 15 minutes Transfer the prepolymer into a suitable vessel to mix it with a suitable chain extender in a defined ratio. The mixing is carried out by stirring with a stirring time of e.g. 20 to 90 seconds. There is a

Chain extension and crosslinking of the molecular chains of the Pre-polymer in an exothermic reaction, so that a high-quality TPU is formed. 5. Final casting into prefabricated parts or blocks, if necessary

Heat treatment and / or cooling. The blocks can be granulated after curing.

Example 2:

1. Filling the Polymerization Reactor with Polyol (one or more)

• additives (if necessary in a specific order);

2. Start degassing, exact temperature control, e.g. to 100 degrees Celsius to liquefy the polyol, and dispersion of the additives in the polyol e.g. by means of a rotating toothed disc; 3. Addition of diisocyanate, e.g. MDi, preferably under monitoring of the reaction profile, in particular the reaction time of e.g. about 15 minutes, and while mixing e.g. by means of the rotating toothed disc; during this reaction time, an exothermic prepolymer reaction takes place; 4. At the end of the predefined reaction time transfer of the prepolymer into a suitable vessel;

5. Add CNT (preferably pre-dried);

6. Start dispersion of the CNTs in the prepolymer, for example by mixing by means of a rotating toothed disk; 7. After a predefined mixing time has elapsed, start mixing with a suitable chain extender. The mixing, eg by continuous mixing in a casting machine, takes place by Stirring within short residence times. In this case, a chain extension and crosslinking of the molecular chains of the prepolymer takes place in an exothermic reaction, so that a high-quality TPU is formed. 8. Final casting into prefabricated parts or blocks and cooling.

Another variant of the process is that the polymerization is carried out in a one-shot process. That is, polyol (containing the premixed ClMTs), diisocyanate and chain scavenger are co-reacted in a container. In a predetermined reaction state, the liquid mixture is poured into molds for solidification.

Example 3:

A commercially available polyol, for example Polycaprolactondiol OH number 56 mg KOH / g, functionality 2, in the liquid state in a dissolver such as Dispermat VL10-C (VMA Getzmann GmbH), equipped with a system for temperature control and evacuation, together with conventional auxiliaries and / or additives and carbon nanotubes (CNT ^' s) in an amount of up to 0.5 percent by weight (wt .-%), based on the finished TPU produced to be introduced. The mixing and dispersing of the CNT especially the ^'s is carried out under vacuum by means of a toothed disk (for example, d = 90 mm, speed continuously 0-6000 l / min) for a given mixing time (dispersion phase). The vacuum is eg controllable up to a pressure p <lmbar. The occurring at the beginning of the evacuation foaming of the mixture supports essentially the breaking up of the agglomerates and the gentle dispersion of the CNTs with a wetting of their surface. After completion of the mixing time, the gas present during foaming is sucked out of the mixture so that it no longer foams. The mixing time is thus chosen at least until no more foam is present.

Typical conditions are pressure p <10 mbar, speed 2500 l / min, mixing time 50 min. After the end of the dispersing phase, e.g. in a prepolymer process, a reaction with diisocyanate, e.g. MDI, and then the prepolymer e.g. drained and with a commercially available chain extender, e.g. BDO, mixed.

Example 4:

In a produced by conventional methods prepolymer, based on eg polycapolactone OH number 56 mg KOH / g and eg MDI, with a ratio in the range between 0.9 and 1.2, CNT's are in an amount up to 0.5 % By weight, based on the finished TPU to be produced. The mixing and especially the dispersion of the CNT's takes place in a stirred tank of zb1501, which can be temperature-controlled and can be evacuated as well as pressurized. A suitably designed toothed disc, eg with diameter d = 250mm, speed infinitely 0 - 400 l / min, leads in connection with negative pressure to a gentle and good dispersion of the CNT ^' s, so that the CIMT ^' s containing prepolymer after eg 40 min over a mixing head with chain extender can be mixed and finished. A method for producing a plastic from a carbon nanotube-containing polymer with the method steps is proposed:

Filling a polymerization reactor with at least one polyol and a diisocyanate to produce a prepolymer,

Mixing the prepolymer with a chain extender to transfer the prepolymer into the polymer in liquid form, and

- Transfer or cooling of the polymer to form the solidified plastic. The carbon nanotubes are added to the prepolymer and / or the polyol before and / or during the mixing of the prepolymer with the chain extender.

The invention is not limited to the embodiments given above. Rather, a number of variants are conceivable, which make use of the features of the invention even with fundamentally different type of execution.

Claims

claims

1. A process for producing a, in particular compact and electrically non-conductive, plastic from a

Carbon nanotube-containing polymer with the process steps:

Filling a polymerization reactor with at least one polyol and a diisocyanate to produce a prepolymer, mixing the prepolymer with a chain extender for

Transferring the prepolymer into the polymer in liquid form, and

Transfer of the polymer to form the solidified plastic, wherein the carbon nanotubes are added to the liquid prepolymer and / or the liquid polyol prior to mixing the prepolymer with the chain extender and / or a carbon having dispersed therein carbon nanotubes is used to charge the polymerization reactor, characterized in that the polyol is degassed prior to the addition of the diisocyanate and / or the prepolymer prior to mixing with the chain extender, the degassing being carried out after the addition of the carbon nanotubes, and gas assisting to generate a negative pressure to assist degassing.

2. The method according to claim 1, characterized in that the degassing is carried out during mixing of the carbon nanotubes with the polyol and / or the prepolymer for their dispersion.

3. The method according to any one of claims 1 to 2, characterized in that after the addition of the carbon nanotubes a touching

Mixing the carbon nanotubes with the polyol or the prepolymer is performed.

4. The method according to any one of claims 1 to 3, characterized in that a crosslinked or thermoplastic polyurethane elastomer is produced as plastic.

5. The method according to any one of claims 1 to 4, characterized in that the polyol is degassed and tempered prior to addition of the diisocyanate.

6. The method according to any one of claims 1 to 5, characterized in that the polyol before degassing at least one additive is added.

7. The method according to any one of claims 1 to 6, characterized in that the carbon nanotubes are added to the polyol before degassing.

8. The method according to any one of claims 1 to 7, characterized in that the transfer of the prepolymer is carried out in the liquid polymer in a Spritzgießcompounder and injection molding of the liquid polymer is carried out, wherein a leading to the solidification of the polymer cooling between the transfer of the prepolymer is avoided in the liquid polymer and injection molding.

9. A process for producing a plastic from a carbon nanotube-containing polymer according to any one of Ansürüche 1 to 8, wherein the polymerization is carried out in a one-shot process, wherein polyol, diisocyanate and a chain extender in a container are reacted together thereby characterized in that the polyol contains pre-mixed carbon nanotubes

10. The method according to any one of claims 1 to 9, characterized in that a solidified, rubber-elastic sealing and / or damping material is produced as plastic.