JP2003504433A - Method and system for producing polyurethane hot melt adhesives - Google Patents

Abstract

(57) Abstract: A polyurethane hot melt adhesive is produced from a known isocyanate (first component A) and at least one second component (B). The two components (A and B) are independently extruded and melted, then they are mixed and reacted with each other. The present invention offers many advantages over the prior art.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a process for the production of polyurethane hot melt adhesives from isocyanates known per se (first component A) and at least one second component B, more particularly continuous production. On how to do.

BACKGROUND OF THE INVENTION Hot melt adhesives (also known as hot melts) are based in particular on polyurethanes, are applied in the molten state and cure particularly quickly upon subsequent cooling. Polyurethane is, in particular, an adhesive system consisting of a polyether diol / polyester diol (component B) and a diisocyanate. The highly variable cure of the polyurethane adhesive is due to the second diol component or atmospheric moisture. Polyurethanes form high strength elastic bonds that can withstand mechanical loads and temperature changes.

The above method is known from the handbook of Reinhard Duespohl Maschinenbau GmbH, which describes a method for the production and immediate application of polyurethane hot melt adhesives. The granules of the two components A and B are fed into the mixing zone from two independent hoppers by means of independently driven metering screws. From this mixing zone, the granules enter an extruder where they are heated to the softening point by compression and friction heat and processed into a homogeneous adhesive composition. This extruder may be followed by a hot melt adhesive application system.

However, despite its obvious advantages, this method is associated with a number of drawbacks. The melting temperature is only filled by the driving energy of the extruder. Therefore, subsequent heating or cooling is required to obtain the desired processing temperature and viscosity. For this purpose, the adhesive must be adjusted to the processing temperature in an intermediate tank and this tank must be covered with an inert gas to prevent premature curing of the adhesive. Cleaning the intermediate tank with a special cleaning agent is another drawback.

After each stop, the machine, and more particularly the extruder, has to be washed. The isocyanate components present in the machine must be completely neutralized, i.e. completely consumed and removed.

The water present in component B leads to a chemical reaction with the isocyanate, during which carbon dioxide is produced leading to foaming. In addition, amines are formed that promote cross-linking of the adhesive, which is probably undesirable.

[0007] Other drawbacks include high energy costs and large losses of adhesive used for machine "rinsing" and relatively long residence time of the adhesive mixture at elevated temperatures.
Also, relatively large amounts of adhesive in the machine are not preferred. Further, improved adhesive systems, such as accelerated systems, thixotropic systems or effervescent systems, if at all possible, are only limited in their manufacture and processing.

The problem to be solved by the invention was therefore to avoid the abovementioned drawbacks in the method described at the outset.

DISCLOSURE OF THE INVENTION According to the invention, the solution of the above-mentioned problems for the method described at the outset consists of two components:
The (A and B) is characterized in that it is metered and transported, preferably extruded, melted, and more particularly simultaneously melted independently of one another, only after this is mixed and reacted.

In this way, improved temperature control is achieved during the melting of components A and B in a separate extruder.

The already melted components A and B can be mixed considerably efficiently. No intermediate tank is needed anymore to bring the adhesive mixture to the desired processing temperature. There is no adhesive in the extruder, only the components necessary to make the adhesive. These components only react with each other in the mixer. The use of inert gas is not necessary. When interrupting this process, only the mixer, not the extruder, needs to be cleaned, resulting in less adhesive loss than in the prior art. When the adhesive cures in the machine, only the mixer, not the extruder, needs to be replaced, thus reducing interruptions compared to known methods. Significantly lower amounts of the manufactured adhesive are present in the machine, resulting in significantly less heat exposure of the adhesive before processing. A relatively constant consistency is achieved.
Finally, it is also possible to prepare improved adhesive systems, in particular unaccelerated or highly accelerated systems, nonfoaming or highly foaming systems and / or nonthixotropic or highly thixotropic systems. Another advantage is that the water present in component B evaporates before contacting this component with the isocyanate.

In another aspect of the invention, components (A and B) can be further heated during extrusion to adjust the desired adhesive temperature as desired.

[0013]   In one advantageous aspect of the invention, a static mixer is used for mixing.

[0014]   In another aspect of the invention, the ingredients are mixed immediately after extrusion.

In another advantageous embodiment, the additional component (C) can be added during the mixing.

Best Mode for Carrying Out the Invention Any isocyanate suitable for the production of adhesives can be used as the first component A. In one particular embodiment, this component is a mono- or polyfunctional or blocked isocyanate.

The second component B can be selected from any available formulation known per se. In one particular embodiment, component B is a substance containing at least two functional groups reactive to isocyanate groups (more specifically polyols). The second component can also be modified to achieve the corresponding properties of the final adhesive (eg, thixotropy, foaming, accelerated curing, etc.).

The quantitative ratio between components A and B should preferably be chosen such that an excess of isocyanate groups is present or an equal ratio is present. Excess isocyanate groups can react with moisture.

The above-mentioned additional component C can be used as another optional component for the particular application. In one embodiment, the additional component (C) is a promoter, a thixotropic agent,
Foaming additives, stabilizers, dyes and / or pigments and / or residual water binding molecular sieves.

In one embodiment, the additional components are added at the beginning of the mixing of the first and second components.

In another advantageous embodiment, the components to be mixed are heated during mixing so that the temperature of the adhesive produced is as desired without depending on the driving energy of the extruder for heating. Allows to be adjusted to.

Finally, in another preferred embodiment, the adhesive is applied to the substrates to be bonded immediately after manufacture, directly or by an application system known per se, optionally with a metering unit in the middle. A related example will be described in detail below.

The present invention relates to a machine for the continuous production of polyurethane hot melt adhesives from a first component and at least one second component, comprising at least one extruder and a mixer connected thereto. This machine is known from the Duespohl handbook mentioned above.

The solution to the above problem is characterized in that a separate extruder is provided for the first and second components, and the outlet of the extruder is connected to the inlet of the mixer.

[0025]   In one preferred embodiment, the extruder is heatable.

In another advantageous embodiment, the mixer is a static mixer, more specifically heatable.

Further advantageous aspects can be found in other dependent claims relating to the machine of the invention.

Examples of aspects of the present invention are described in detail below with reference to the accompanying drawings. Since the same reference numerals have the same meanings in all the drawings, they will be described only once.

The machine shown in FIG. 1 comprises an extruder 1 with a drive 3 for component A (isocyanate), an extruder 2 with a drive 4 for component B, a static mixer 5, a mixer 5 It comprises a supply device (not shown) for supplying the component C to the, and a control unit (also not shown). The temperature of the adhesive or components and the speed of rotation of the extruder are
It is controlled and displayed by this control unit. Components A and B are for extruder 1
And outlets 2 and 2 via heating pipes 6 to corresponding inlets of the static mixer 5. A shut-off valve in the pipe 6 can be used for cleaning the machine. The valve 7 can be operated manually or pneumatically.

Components A and B are fed from feed hopper 8 to respective extruders 1 and 2. The extruders 1 and 2 can be heated.

In the machine shown in FIG. 1, the static mixer 5 comprises an adhesive application gun 9 known per se.
Are directly linked to. Here, the final adhesive is taken out in the form of droplets (granules) or applied directly to the substrates to be bonded or fed to an adhesive application roller connected to an application gun. You can

FIG. 2 is a longitudinal sectional view of a static mixer 5 capable of continuous heating and including temperature control. The housing consists of a steel tube 10 with an anti-stick coating on the inside. The mixing element 11 (the so-called internal part) is provided with the same or a corresponding coating. The mixing element 11 may, for example, consist of plastic (polyaramid), ceramic or steel.

The static mixer 5 allows component A to be mixed with component B to obtain a homogeneous end product. The addition of component C can influence the physical properties of the final product. The mixing element 11 can be easily, quickly and conveniently removed and replaced for cleaning. For this purpose, the steel tube 10 is provided with its threaded closure 12 at its lower end (in FIG. 2).

FIG. 3 shows a machine similar to that shown in FIG. However, in FIG. 3, the mixer 5 is connected to an adhesive application unit 13 having slot nozzles. This aspect is advantageous when the exact amount of adhesive has to be applied.

Finally, FIG. 4 shows a system similar to that shown in FIGS. 1 and 3. However, in FIG. 4, the static mixer 5 is connected to a gear pump metering station 14 capable of accurately measuring the applied amount of adhesive. The adhesive is discharged from the nozzle 15.

The final products processed are moisture-curable polyurethane adhesives, which can be further specially modified. For example, they can be fast-curing, thixotropic and / or effervescent. Preferred applications of these adhesives include, for example, various substrates, surface lamination of sandwich elements, caravan construction, garage door assembly, mobile home construction, wide section profile exterior (e.g. continuous door manufacturing), Includes three-dimensional stacking and the like.

[Brief description of drawings]

FIG. 1 is a schematic view of a machine of the present invention connected to an adhesive gun.

FIG. 2 is a vertical sectional view of a static mixer used in the machine shown in FIG.

FIG. 3 is a schematic view of a machine corresponding to FIG. 1 connected to a slot-like adhesive coating unit.

FIG. 4 is a schematic diagram of a machine corresponding to FIG. 1 with an additional adhesive metering station.

[Explanation of symbols]

1 extruder 2 extruder 3 drive 4 drive 5 mixer 6 pipes 7 Shut-off valve 8 supply hopper 9 Adhesive application gun 10 steel tube 11 mixed elements 12 closures 13 adhesive applicator 14 Metering gear pump station 15 nozzles A first component B second component C additional component

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Andrew Nixon             Federal Republic of Germany Day-40670             Shu, Atzare Envek No. 28 F-term (reference) 4G035 AC01 AE13 AE15                 4J040 EF051 EF261 EF331 JB01                       KA17 KA25 KA35 KA37 QA01                       QB04

Claims (12)

[Claims] 1. An isocyanate known per se (first component A) and at least 1
A process for the production of a polyurethane hot melt adhesive from two second components (B), more particularly a continuous production, wherein the two components (A and B) are metered and transported, preferably Extrudes, melts,
More specifically, a method characterized in that they are simultaneously melted independently of each other and mixed and reacted only after this. 2. A process according to claim 1, characterized in that the components (A and B) are additionally heated during extrusion. 3. A method according to claim 1 or 2, characterized in that a static mixer is used for the mixing. 4. The method according to claim 1, wherein the components (A and B) are mixed immediately after extrusion. 5. An additional component (C) is added during mixing.
The method according to any one of to 4. 6. The method according to claim 1, wherein the first component (A) is a monofunctional or polyfunctional or blocked isocyanate. 7. The second component (B) is a substance containing at least two functional groups reactive with an isocyanate group, more specifically a polyol, according to any one of claims 1 to 6. The method described in crab. 8. The additional component (C) is a promoter, a thixotropic agent, a foaming additive,
Process according to any of claims 5 to 7, characterized in that it is a stabilizer, a dye and / or a pigment and / or a molecular sieve for binding residual water. 9. The method according to claim 5, wherein the additional component (C) is added when the mixing of the first component (A) and the second component (B) is just started. The method described. 10. The method according to claim 1, wherein the components to be mixed are heated during the mixing. 11. Adhesive is applied to the substrates to be bonded directly immediately after manufacture or by an application system known per se, optionally with a metering unit in the middle. 11. The method according to any one of 10. 12. A polyurethane hot melt adhesive from a first component (A) and at least one second component (B) comprising at least one extruder (1, 2) and a mixer (5) connected thereto. A machine for the continuous production of an agent, wherein an independent extruder (1, 2) is provided for the first and second components (A and B), and the outlet of the extruder (1, 2) A machine characterized in that it is connected to the inlet of the mixer (5).