DE10146395B4 - Continuous process for the preparation of RTV-1 compounds - Google Patents

Abstract

method for the continuous production of homogeneous RTV-1 masses, at in one step with a single pass through the one Rotor-stator system existing mixing zone of a mixer α, ω-dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C) are mixed together, the registered by the raw materials Water in the mixing zone completely reacts with the crosslinker and no in the RTV-1 masses Raw materials trapped water more evidence.

Description

The The invention relates to a process for continuous production of homogeneous RTV-1 masses in a mixer with a rotor-stator system existing mixing zone.

organopolysiloxane, which are storable under exclusion of moisture and under access of moisture at room temperature, so-called RTV-1 compounds, have been known for a long time.

Various processes are known for the preparation of RTV-1 compounds. Because of the high productivity, continuous processes are particularly preferred. The problem to be solved in particular is the continuous and homogeneous mixing of fillers into the highly viscous polymer components, especially when they are reinforcing fillers with large surfaces. Mixing must be done in such a way that no filler particles are visible in the finished product. Another difficulty is the water introduced with the fillers, which, if the mixture is not homogeneous, by local over-concentration of the water for several days after the mixture preparation to form inhomogeneities by crosslinking the RTV-1 mixture to the non-homogeneously mixed Can cause filler particles around. For example, in the EP 234 226 A2 in a first step, part of the constituents are combined in a continuously operating closed mixer and, in a second step, the remaining constituents are metered into an oscillating pilgrim step kneader and the mass is homogenized in this kneader. In order to allow reaction times between the individual mixing steps, a further three-stage process has been developed in addition EP 940 445 A1 described. In EP 739 652 A1 describes a process that does not require such a reaction time, but relies on the fact that the water contained in the mixture, which is introduced via the raw materials, must be removed in a step downstream of the mixture preparation. Since the water can still be detected in the compounds, it appears that the mixing in of the fillers with the used aggregate is not sufficient. The mixture contains not completely wetted filler particles in which the water is. When the mixture is complete, the water reacts irreversibly with the crosslinker and thus could no longer be detected.

Another in EP 688 598 B1 described method uses a specially designed, consisting of two mixing chambers mixer in which first a mixture of liquids and a powder in a first, upper mixing chamber is prepared, whereupon in the second, lower mixing chamber, the mixture for the purpose of homogenization by a second independent mixing element sheared again and further liquid components are mixed.

In EP 10 08 613 A2 describes the use of an axial flow mixing turbine. This mixing turbine has already been in EP 234 226 A2 used in combination with a pilgrim stepper. Although the mixing results by means of such a mixer are excellent, a significant disadvantage is that these types of mixers are not self-cleaning, that is to say that inside the mixer deposits of filler and liquid are formed, which are already more than 24 hours Operation leads to a deterioration of the sealant quality by filler particles. This problem can only be solved by frequent regular cleaning of the mixing turbine.

Furthermore, for example US 3,194,540 Mixers known that operate on the rotor-stator principle. Such mixers are used both for emulsion production and for incorporation of solids in liquids. In these devices, a rotor rotates within a stationary stator. The stator has slots that can be variable in width. The rotor may also have such slots, which may be supplemented by evolute conveying elements. It may also be present only the conveying elements. The rotor sucks the material and hurls it radially, if necessary through its and the slots of the stator to the outside. The stator teeth, which limit its slots, act as an impact surface and the gap between the rotor and the stator causes shearing. These mixers are usually designed so that you can install up to three rotor-stator pairs in a row, each with different slot widths. The more demanding the dispersing task, the more tools with narrower slot widths are built.

Of the Invention is based on the object, a method for continuous To provide preparation of RTV-1 masses, the production in a single step using a standard mixer, the without intermediate cleaning over can be operated for a long period of time.

The invention relates to a process for the continuous production of homogeneous RTV-1 compositions, wherein in one step in a single pass through the mixing zone of a mixer consisting of a rotor-stator system α, ω- dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C) are mixed together, wherein the water introduced by the raw materials in the mixing zone completely reacts with the crosslinker and in the RTV-1 mass no entrained by raw water Show more.

It It has now been found that one out of a single rotor-stator system existing mixing zone is ideally suited to RTV-1 compositions already in such a quality which does not require any remixing for the purpose of further homogenization requires. It is not necessary that the rotor itself Owns mixing elements. Reaction times between individual mixing steps are not mandatory. The water introduced by the raw materials reacts completely in the mixing zone with the crosslinker and therefore need not be removed later. The homogeneity in terms of filler incorporation and storage stability the RTV-1 mixtures are excellent.

Also during storage of the mixtures thus prepared do not form magnifying Particles formed by reaction of unfilled wetted filler particles water could be formed with the RTV-1 mass.

As α, ω-dihydroxypolydiorganosiloxane (A), preference is given to linear α, ω-dihydroxypoly (diorganosiloxanes) of the general formula (I) HO- [R ₂ SiO] _m -H (I), used in which
R denotes monovalent C ₁ -C ₈ -hydrocarbon radicals which are optionally substituted by fluorine, chlorine, bromine, C ₁ -C ₄ -alkoxyalkyl or cyano groups and
m means values corresponding to a viscosity of the HO-terminated organopolysiloxane (A) of 0.05 to 1000 Pa · s.

Examples for hydrocarbon radicals R are linear and cyclic saturated and unsaturated Alkyl radicals, such as the methyl radical, aryl radicals, such as the phenyl radical, alkaryl radicals, such as tolyl radicals and aralkyl radicals, such as the benzyl radical.

Prefers as the radical R are unsubstituted hydrocarbon radicals with 1 to 6 carbon atoms, with the methyl radical being particularly preferred.

The Organopolysiloxanes (A) preferably have a viscosity of 100 up to 700000 mPa · s, in particular from 20,000 to 350,000 mPa · s, measured in each case at 23 ° C.

Preferably be in the process at least 40, in particular at least 50 wt .-% and preferably at most 90, in particular at most 80 wt .-% organopolysiloxane (A) used.

As crosslinkers (B) are preferably used in the process silanes which have condensable groups with the hydroxyl groups of the α, ω-dihydroxypolydiorganosiloxane, and oligomeric condensation products of these silanes. In particular, as crosslinkers (B) are used silanes of the general formula (II) R ¹ _n SiX _(4-n) (II), in the
R ¹ monovalent, optionally with fluorine, chlorine, bromine, C ₁ -C ₄ alkoxyalkyl, amino-C ₁ -C ₆ alkyl, amino-C ₁ -C ₆ -alkylenamino- or cyano groups substituted C ₁ -C ₁₀ hydrocarbon radicals,
X is hydrogen, fluorine, chlorine or bromine atoms, C ₁ -C ₄ -alkoxy, C ₁ -C ₄ -acyloxy, amino, C ₁ -C ₄ -alkylamino, C ₁ -C ₄ -dialkylamino-, -C ₁ -C ₆ -alkylamido-, - (NC ₁ -C ₄ -alkyl) -C ₁ -C ₆ -alkylamido or Si-ON = bonded C ₃ -C ₆ -ketoximo groups and

n the values 0, 1 or 2 mean.

Preferably in the process at least 0.5, in particular at least 2 wt .-% and preferably at most 15, in particular at most 10 wt .-% crosslinker (B) used.

Examples of fillers (C) are non-reinforcing fillers, ie fillers having a BET surface area of up to 50 m ² / g, such as carboxylic acid-coated chalks, quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolites, metal oxide powder such as aluminum, titanium, iron - or zinc oxides or their mixed oxides, barium sulfate, calcium carbonate, gypsum, silicon nitride, silicon carbide, boron nitride, glass and plastic powder, such as polyacrylonitrile powder; reinforcing fillers, ie fillers having a BET surface area of more than 50 m ² / g, such as fumed silica, precipitated silica, carbon black, such as furnace and acetylene black, and silicon-aluminum mixed oxides with a large BET surface area; fibrous fillers such as asbestos as well as plastic fibers.

The mentioned fillers (C) can be hydrophobic, for example by treatment with organosilanes or siloxanes or with stearic acid or by etherification from hydroxyl groups to alkoxy groups. It can be a kind of filler, It is also possible to use a mixture of at least two fillers.

Preferably in the process at least 2, in particular at least 5 wt .-% and preferably at most 40, in particular at most 15 Wt .-% filler (C) used.

The addition of other ingredients, such as Example catalysts, pigments and fungicides is possible. Further constituents can also be mixed in a further process step.

The preferred method is with 1 In a rotor-stator mixing device ( 5 ) are fed through the inlet ( 6 ) α, ω-dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C) are metered in free fall.

The mixing tools of the mixing device ( 5 ) comprise the stator ( 2 ), which recesses, preferably comb-like recesses and the rotor ( 3 ), which has recesses, in particular comb-like recesses and / or conveying elements, in particular evolute-shaped conveying elements, and which by the drive shaft ( 1 ) is driven. Between stator ( 2 ) and rotor ( 3 ) there is a gap. Dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C) are passed through the rotor ( 3 ) and through the recesses of rotor ( 3 ) and stator ( 2 ), the mixture being sheared vigorously. On the way to the outlet ( 4 ) no further mixing energy is supplied to the product.

After passing the mixing device once ( 5 ) no disturbing inhomogeneities can be determined.

Of the Term polysiloxanes in the context of the present invention dimer, oligomeric and polymeric siloxanes.

in the described below, all figures are from Share with percentages, unless otherwise stated, by weight. Further relate all viscosity information on a temperature of 25 ° C. Unless otherwise indicated, the following examples are at a pressure of the surrounding atmosphere, ie at about 1000 hPa, and room temperature, ie at about 20 ° C, or at a temperature, when mixing the reactants at room temperature without additional Heating or cooling adjusts.

In a rotor-stator mixing unit ( 5 ) are fed through the inlet ( 6 ) 730 kg / h of a mixture of 71% of an α, ω-dihydroxypolydimethylsiloxane having a viscosity of 80,000 mPas, 23.5% of an α, ω-bis-trimethylsiloxypolydimethylsiloxane having a viscosity of 100 mPas and 5.5% of an oligomer mixture of acetoxysilanes (Crosslinker ES 24 of Wacker-Chemie GmbH, Munich) and 62 kg / h of a fumed silica having a BET surface area of 150 m ² / g in free fall. The mixing unit is operated at a speed of 2500 min ^-1 . The rotor ( 3 ) has only 6 evolute conveying elements, but no mixing elements. After one time, the mixing tools of the stator, which are designed as comb-like recesses (42 teeth with a width of 13 mm and a distance of 9 mm), pass through ( 2 ) (Inner diameter 275 mm) are no longer disturbing inhomogeneities to determine. On the way to the discharge ( 4 ) no further mixing energy is supplied to the product. The mixture remains homogeneous even when stored for an extended period of time. There are no inhomogeneities due to local crosslinking of the mixture. This means that the mixture contains no more water.

Even after 12 weeks of uninterrupted operation of the device according to 1 , No change in the sealant quality was found, ie no disturbing impurities are deposited in the device itself, which could make the sealant unusable in the event of uncontrolled detachment.

Claims (6)

Process for the continuous production of homogeneous RTV-1 masses, where in one step in a single pass by the mixing zone of a mixer α, ω-dihydroxypolydiorganosiloxane consisting of a rotor-stator system (A), crosslinker (B) and filler (C) are mixed together, wherein the water introduced by the raw materials completely in the mixing zone reacts with the crosslinker and no in the RTV-1 masses Raw materials trapped water more evidence. A process as claimed in claim 1, wherein α, ω-dihydroxypolydiorganosiloxane (A) comprises linear α, ω-dihydroxypoly (diorganosiloxanes) of the general formula (I) HO- [R ₂ SiO] _m -H (I), in which R denotes monovalent C ₁ -C ₈ -hydrocarbon radicals which are optionally substituted by fluorine, chlorine, bromine, C ₁ -C ₄ -alkoxyalkyl or cyano groups and m means those which have a viscosity of the HO-terminated one Organopolysiloxane (A) of 0.05 to 1000 Pa · s correspond. Method according to claim 1 or 2, wherein 40 to 80% by weight of organopolysiloxane (A) are used. A process as claimed in any of claims 1 to 3, wherein crosslinkers (B) comprise silanes which have groups condensable with the hydroxyl groups of the α, ω-dihydroxypolydiorganosiloxane and also oligomeric con condensation products of these silanes are used. The method of claim 1 to 4, wherein the 0.5 to 15 wt .-% crosslinker (B) are used. The method of claim 1 to 5, wherein 2 to 40 Wt .-% filler (C) are used.