EP2791948A1

EP2791948A1 - Method for producing composite insulators by uv-crosslinking silicone rubber

Info

Publication number: EP2791948A1
Application number: EP12791489.3A
Authority: EP
Inventors: Jens Lambrecht; Georg Simson; Hans-Jörg WINTER
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2011-12-12
Filing date: 2012-11-28
Publication date: 2014-10-22
Anticipated expiration: 2032-11-28
Also published as: WO2013087414A1; JP2015508422A; US20140296365A1; CN103930955A; KR101639231B1; DE102011088248A1; EP2791948B1; US9236164B2; KR20140074340A

Abstract

The invention relates to a method for producing composite insulators. A support component is provided with a shielding element made of silicone rubber. The invention is characterized in that the crosslinking of the silicone rubber is initiated by means of UV irradiation.

Description

METHOD FOR THE PRODUCTION OF COMPOSITE INSULATORS

UV NETWORKING OF SILICONE RUBBER

The invention relates to a process for the preparation of

Composite insulators with UV-crosslinked shields

Silicone rubber,

Silicone elastomer composite insulators and methods for their preparation are known. Silicone rubber injection molding with so-called solid rubber (HTV high temperature crosslinking or HCR high consistency rubber) is characterized by injecting silicone rubber of comparatively high viscosity into heated molds. The method is e.g. described in EP 1091365 for so-called hollow insulators. The process is used today for all types of components, e.g. also used rod insulators and surge arrester. In this process, the sometimes long cycle times caused by the parts to be wrapped (such as fiber reinforced epoxy rods or tubing), in particular the metallic protruding sometimes out of the mold also up to the crosslinking temperature of the

Rubber must be heated. For large components, machines and devices of considerable dimensions are sometimes necessary.

Another drawback is the presence of parting seams on the molded part, which often require mechanical post-processing of the molded parts.

A similar process can be used using lower pressure machines and so-called liquid rubbers (LSR),

In terms of time, a little earlier and thus before the availability of large injection molding machines are to be classified procedures which umbrellas (DE 2746870) and partly the Strunkumhüllung (EP 1130605) are manufactured individually and then assembled. Here too, mainly solid rubbers are used. Advantages of the methods are the flexibility of the arrangement of the screens. As a disadvantage, the many steps and the high number of connection points screen-Strunkisolierung or screen-screen effect.

Also using solid rubber, methods of making spiral shields are used (EP 821373). Although this method is universally applicable, but may have the disadvantage that also arises from eder Lage to each other layer a junction. The method is not completely automatable,

The early methods, all of which can be referred to as casting methods (DE 2044179, DE 2519007), require the

Use of comparatively low viscosity rubbers. So-called room temperature vulcanizing 2-component rubber (RTV-2) is commonly used, which can be crosslinked in use at slightly elevated temperature. Because with everyone

Operation a single screen is made this is

Method largely independent of the final size of the component applicable. Therefore, this technology can be usefully applied today for very large diameter insulators. There are no longitudinal seams requiring post-processing. A disadvantage is the long cycle time determined by the comparatively low crosslinking rate of the rubbers used.

All known methods have in common that the electrically insulating material of the outer shell of the insulators either automatically at room temperature or thermally initiated at is crosslinked at elevated temperature. The crosslinking at room temperature (eg possible in the conventional methods with open molds according to DE 2044179 and DE 2519007) takes several tens of minutes to a few hours, the crosslinking at elevated temperature requires a period of some

Minutes to several tens of minutes in the molding processes (EP 1147525, DE 2746870 and EP 1091365) up to more than 100 minutes on subsequent crosslinking in an oven, e.g. according to the method described in EP 821373 and EP 1130605.

The invention relates to a method for the production of composite insulators, in which a supporting member is provided with a screen of silicone rubber, characterized in that the crosslinking of the silicone rubber is initiated by UV irradiation.

The crosslinking initiated by UV irradiation of the silicone rubber minimizes cure times, is universally applicable to any composite insulator mold, and thereby from the viewpoint of overall manufacturing cost to the user

advantageous.

There are lower handling costs, lower system costs and no post-processing. The process can be used both for small production series and for large series.

As a supporting component, for example, a

Plastic moldings suitable, which is preferably fiber-reinforced. The supporting member is preferably stretched, i. the ratio length: diameter is at least 2: 1,

in particular at least 3: 1, preferably the supporting component is cylindrical, in particular a rod or tube. In particular, a f-reinforced plastic rod or a f-reinforced plastic tube are used.

The silicone rubber is preferably low in viscosity. Of the

Silicone rubber is filled into a suitable open mold which is guided along the support member to be screened and suitably sealed downwardly so that the silicone rubber can not flow out during filling. After completion of the filling or after reaching a certain level is an exposure or

Intermediate exposure or pre-exposure of the silicone rubber to ultraviolet radiation. The rubber in the casting mold is crosslinked very quickly. The exposure of the silicone rubber to UV radiation should be carried out appropriately so that the

Silicone rubber volume is irradiated so that results in a uniformly fast cross-linking. Preferably, the silicone rubber is irradiated from the open side of the mold. In a likewise preferred

Embodiment consists of the mold of UV-transparent material or the mold has UV-transparent windows and the silicone rubber is irradiated through the mold.

Preferably, certain points in the later screen are additionally irradiated from other directions than from above. The windows may, for example, be mounted laterally of the casting mold and / or below the casting mold. The irradiation from one direction may optionally

be disadvantageous. To ensure uniform irradiation of the

Silicon rubbers can achieve this from several

Directions are completely irradiated. The silicone rubber-filled mold can be exposed in one or more steps. Depending on the size and shape of the umbrellas to be produced, it may be necessary to use different irradiation regimes for the

Crosslinking of the silicone rubber to apply. The irradiation can be carried out after completion of the filling or after reaching a certain partial level of silicone rubber in the casting mold.

The material supply for the silicone rubber to the mold may be wrapped or not wrapped.

The irradiation device initiating the crosslinking can be arranged in the material supply for the silicone rubber. In this embodiment, the to be processed

So that its cross-linking is suitably delayed and, after its irradiation, allows the filling of the casting mold,

A heating device can be arranged around the material feed, below, laterally or above the casting mold, in order to accelerate the crosslinking of the irradiated silicone rubber by heating.

The UV irradiation preferably takes place at at least 0 ° C., particularly preferably at least 10 ° C., in particular at least 15 ° C. and preferably at not more than 50 ° C., particularly preferably at most 35 ° C., in particular not more than 25 ° C.

The irradiation time is preferably at least 1 second, more preferably at least 5 seconds, and preferred

at most 500 seconds, more preferably at most 100 Seconds. The onset of hydrosilylation reaction, the crosslinking of the silicone mixture begins - it gels and hardens. The silicone rubber preferably has a viscosity [D = 0.9 / 25 ° C] of at least 100 mPas, in particular at least 1000 mPas, preferably at most 40,000 mPas, in particular at most 20,000 mPas. The wavelength of the UV radiation is preferably 200 to 500 nm.

The silicone rubber may be a mixture composed of 2 components or of only 1 component.

Preferably, the silicone rubber contains:

(A) containing at least two alkenyl groups per molecule

Polyorgano iloxane with a viscosity at 25 ° C from 0.1 to

500,000 Pa.s,

(B) containing at least two SiH functions per molecule

Organosilicon compound and

(C) by light from 200 to 500 nm activatable platinum group catalyst. The composition of the alkenyl group-containing

Polyorganosiloxane (A) preferably corresponds to

average general formula (1) l _x 2 _y SiO ( ₄ " _x " _y) / 2 (1), in the

a monovalent, optionally halogen or

cyano-substituted, optionally via an organic divalent group bonded to silicon

Hydrocarbon radical containing aliphatic carbon-carbon multiple bonds,

R2 is a monovalent, optionally halogen or

cyanosubstituted over Sic-bonded C] _ - C] _ Q "

Hydrocarbon radical that is free of aliphatic

Carbon-carbon multiple bonds

x is such a nonnegative number that at least two residues

R ^{1 are present} in each molecule, and

y is a non-negative number such that (x + y) is in the range of 1.8 to 2.5.

The alkenyl groups R ¹ are accessible to an addition reaction with a SiH-functional crosslinking agent. Usually, alkenyl groups having 2 to 6 carbon atoms, such as vinyl, allyl, methallyl, 1-propenyl, 5-hexenyl, ethynyl, butadienyl, hexadienyl, cyclopentenyl, cyclopentad enyl, cyclohexenyl, preferably vinyl and allyl, are used. Organic divalent groups, via which the alkenyl groups R - * - may be bonded to silicon of the polymer chain, consist for example of oxyalkylene units, such as those of

general formula (2)

- (0) _m [{CH ₂ ) _n 0] _o - (2), in the

m the values 0 or 1, in particular 0,

n values from 1 to 4, in particular 1 or 2 and

o mean values of 1 to 20, in particular from 1 to 5.

The oxyalkylene units of the general formula (10) are bonded to the left of a silicon atom. The radicals R ¹ may be bonded in any position of the polymer chain, in particular at the terminal silicon atoms, examples of unsubstituted radicals R ^ are alkyl radicals such as methyl, ethyl, n-propyl, iso-propyl, n-butyl -, iso-butyl, tert. Butyl, n-pentyl, iso-pentyl, neo-pentyl, tert. Pentyl radical, hexyl radicals, such as the n-hexyl radical, heptyl radicals, such as the n-heptyl radical, octyl radicals, such as the n-octyl radical and iso-octyl radicals, such as the 2, 2, -trimethylpentyl radical, nonyl radicals, such as the n-nonyl radical, decyl radicals, as the n-decyl radical; Alkenyl radicals such as the vinyl, allyl, η 5-hexenyl, 4-vinylcyclohexyl and 3-norbornenyl radicals; Cycloalkyl radicals, such as cyclopentyl, cyclohexyl, 4-ethylcyclohexyl, cycloheptyl radicals,

Norbornyl radicals and methylcyclohexyl radicals; Aryl radicals, such as the phenyl, biphenylyl, naphthyl radical; Alkaryl radicals, such as o-, m-, p-tolyl radicals and ethylphenyl radicals; Aralkyl radicals, like the

Benzyl radical, the alpha- and the ß-phenylethyl radical,

Examples of substituted Kohlenwasserstof radicals as radicals R2 are halogenated hydrocarbons, such as chloromethyl, 3-chloropropyl, 3-bromopropyl, 3, 3, 3-trifluoropropyl and

5, 5, 5, 4, 3, 3-hexafluoropentyl radical and the chlorophenyl, dichlorophenyl and trifluorotolyl radical.

R2 preferably has 1 to 6 carbon atoms.

Particularly preferred are methyl and phenyl,

Component (A) may also be a mixture of various

Älkenylgruppen containing polyorganosxloxanes be, for example, the alkenyl group content, the nature of

Alkenyl group or structurally different. The structure of the alkenyl-containing polyorganosiloxanes (A) may be linear, cyclic or branched. The content of tri- and / or tetrafunctional units leading to branched polyorganosiloxanes is typically very low, preferably at most 20 mol%, in particular at most 0.1 mol%.

Most preferably, the use is vinyl groups

containing polydimethylsiloxanes whose molecules of the

general formula (3)

(ViMe ₂ Si0 _{_1/2)} 2 (ViMeSiO) _p (Me ₂ SiO) (3), corresponding to the non-negative integers p and q are the following relations meet: p> 0, 50 <(p + q) <20,000, preferably 200 <(p + q) <1000, and 0 <(p + l) / (p + q) <0.2.

The viscosity of the polyorganosiloxane (A) at 25 ° C is preferably 0.5 to 100,000 Pa-s, in particular 1 to 2000 Pa-s.

The at least two SiH functions per molecule containing organosilicon compound (B), preferably has a

Composition of the average general formula (4)

H _a R ³ bSiO ( ₄ -ab) / 2 (4), in

a monovalent, optionally halogen or

cyano-substituted, SiC-bonded Ο ^ -Ο β-

Hydrocarbon radical that is free of aliphatic

Carbon-carbon multiple bonds and

a and b are nonnegative integers, with the proviso that 0.5 <(a + b) <3, 0 and 0 <a <2, and that at least two silicon-bonded hydrogen atoms are present per molecule. Examples of R3 are the radicals indicated for R ^. R 1 preferably has 1 to β carbon atoms. Particularly preferred are methyl and phenyl,

Preferred is the use of an organosilicon compound (B) containing three or more SiH bonds per molecule. When using only two SiH bonds per molecule

containing organosilicon compound (B), the use of a polyorganosiloxane (A), which has at least three alkenyl groups per molecule is recommended.

The hydrogen content of the organosilicon compound (B), which refers exclusively to the hydrogen atoms bonded directly to silicon atoms, is preferably in the range of 0.002 to 1.7% by weight of hydrogen, preferably 0.1 to 1.7% by weight of hydrogen ,

The organosilicon compound (B) preferably contains

at least three and at most 600 silicon atoms per molecule. Preferred is the use of organosilicon compound (B) containing 4 to 200 silicon atoms per molecule.

The structure of the organosilicon compound (B) may be linear, branched, cyclic or network-like. Particularly preferred organosilicon compounds (B) are linear polyorganosiloxanes of the general formula (5)

(HR4 ₂ Si0 _{_1/2)} c (R ⁴ 3SiOi / 2) d (HR ⁴ Si02 / 2) eCR ⁴ 2Si0 _2/2) f (5), in which

R.4 has the meanings of and

the nonnegative integers a, d, e and f following

Satisfy relations: (c + d) = 2, (c + e)> 2, 5 <(e + f) <200 and 1 <θ / (e + £) <0, 1.

The SiH-functional organosilicon compound (B) is

preferably in such an amount in the crosslinkable

Silicone compound contain that the molar ratio of SiH groups to alkenyl groups at 0.5 to 5, in particular from 1.0 to 3.0.

As catalyst (C) it is possible to use all known platinum group catalysts which catalyze the hydrosilylation reactions taking place during the crosslinking of addition-crosslinking silicone compositions and which can be activated by light of 200 to 500 nm.

The catalyst (C) contains at least one metal or compound of platinum, rhodium, palladium, ruthenium and

Iridium, preferably platinum.

Particularly suitable catalysts (C) are cyclopentadienyl complexes of platinum, preferably of the general formula (6)

9b

in which

g 1 to 8,

h 0 to 2, i = 1 to 3,

R ^{7 are} independently, identically or differently, a monovalent unsubstituted or substituted, linear, cyclic or branched, aliphatic

saturated or unsaturated or aromatically unsaturated radicals containing hydrocarbon radical having 1 to 30 carbon atoms, in which individual carbon atoms may be replaced by O, N- _f S or P atoms,

R8 independently, identical or different hydrolyzable functional groups selected from the group containing

Carboxy-O-C (O) R ¹⁰ ,

Oxime -ON = CR ¹⁰ ₂ ,

Alkoxy -OR ¹⁰ ,

Alkenyloxy -OR ¹²

Amide -NRiO-CfOjR ¹¹ ,

Amine -NR ¹⁰ R ^{1: 1} -,

Aminoxy-O-R ^ R ¹¹ , with

R 1 independently of one another, identical or different, are H, alkyl, aryl, arylalkyl, alkylaryl,

R 1 -I independently of one another, identically or differently, alkyl, aryl, arylalkyl, alkylaryl,

R ^ 2 is a linear or branched, aliphatically unsaturated organic radical,

R ^ ^{A are} independently, identically or differently alkyl, aryl, arylalkyl, alkylaryl having 1 to 30 carbon atoms, wherein the hydrogens may be substituted by -Hai or -SiR3 ⁹ , with

R9 independently, identically or differently, a monovalent, unsubstituted or

substituted, linear, cyclic or branched hydrocarbon radical,

R ^ k are independent of each other, the same or different

Hydrogen or a monovalent, unsubstituted or substituted, linear or branched, aliphatic saturated or unsaturated or aromatic unsaturated radicals containing hydrocarbon radical having 1 to 30 carbon atoms, in which individual carbon atoms can be replaced by 0, N, S or P atoms and can form the rings fused with the cyclopentadienyl radical.

Preferred radicals R 1 are linear saturated

Hydrocarbon radicals having 1 to 8 carbon atoms. Further preferred is the phenyl radical.

Preferred radicals R 1 are methoxy, ethoxy, acetoxy and 2-methoxyethoxy groups. Preferred radicals R ^ ^a are linear and branched,

optionally substituted alkyl radicals such as methyl, ethyl, propyl or butyl radicals.

Preferred radicals R 1b are linear and branched,

optionally substituted linear alkyl radicals such as methyl, ethyl, propyl or butyl radicals. Further preferred are further substituted fused rings such as the indenyl or fluorenyl. Particularly preferred as catalyst (C) is MeCp (PtMe3).

Catalyst (C) can be used in any desired form, for example also in the form of

Hydrosilylation catalyst-containing microcapsules, or organopolysiloxane particles as described in EP-A-1006147.

The content of hydrosilylation catalysts (C) is

preferably chosen so that the silicone rubber is a content has platinum group metal of 0.1-200 ppm, preferably 0.5-40 ppm.

The silicone rubber: is preferably transparent to UV radiation of 200 to 500 nm and in particular free of UV radiation of 200 to 500 nm absorbing fillers.

However, the silicone rubber may also contain filler (D). Reinforcing fillers, ie fillers having a BET surface area of at least 50 m ² / g, are, for example, fumed silica, precipitated silica, carbon black, such as

Furnace and acetylene black and silicon-aluminum mixed oxides large BET surface area. Fiber-shaped fillers are

For example, asbestos and plastic fibers. The fillers mentioned may be hydrophobic, for example by treatment with organosilanes or siloxanes or by

Derivative of hydroxyl groups to alkoxy groups. Examples of non-reinforcing fillers (D) are fillers with one

BET surface area of up to 50 m ² / g, such as 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. It can be a kind of filler, it can also be a mixture of at least two fillers used.

When the silicone rubber contains filler (D), its content is preferably 1 to 60% by weight, especially 5 to 50% by weight. -%.

The silicone rubber may contain as component (E) further additives in an amount of up to 70% by weight, preferably 0.0001 to 40% by weight. These additives can eg resinous Polyorganosiloxanes, which are different from the diorganopolysiloxanes (A) and (B), dispersing aids, solvents, adhesion promoters, pigments, dyes, plasticizers, organic polymers, heat stabilizers, etc. These include additives such as dyes, pigments, etc. Furthermore, as

Component (E) thixotropic ingredients such as finely divided silica or other commercially available Thixotropieadditive be contained.

In addition, as a chain extender siloxanes the

Formula HSi (CH ₃₎ ₂ - [O-Si (CH3) _2] _W may be present -H, where w is from 1 to 1000 means.

It may also contain additions (E), which the

purposeful adjustment of the processing time, light-off temperature and crosslinking speed of the silicone rubber serve. These inhibitors and stabilizers are well known in the field of crosslinking compositions.

In addition, it is also possible to add additives which improve the compression set. In addition, you can also

Hollow bodies are added. In addition, you can also

Be added blowing agent for the production of foams.

In addition, not vinyl-functionalized

Polydiorganosiloxanes are added.

The compounding of the silicone rubber is carried out by mixing the above listed components in any order.

All described technologies can be combined with the appropriate ones

Machines and devices also for other components than

Composite insulators, such as e.g. also for the serving of

Abieiteraktivteilen be applied. All the above symbols of the above formulas each have their meanings independently of each other. In all formulas, the silicon atom is tetravalent. Embodiments of the invention will be described with reference to the

Figures Fig. 1 to 4 demonstrated.

The meanings of the reference numerals are listed below 1 - bearing component

2 - silicone rubber

3 - casting mold

4 - Irradiation device

5 - UV-transmitting or UV-transparent windows

provided mold

1 shows the roughly schematic arrangement of the UV irradiation device above the casting mold.

The silicone rubber filled in the casting mold is exposed in such a way that its fast cross-linking is initiated. The mold does not have to be transparent to the UV radiation in this arrangement. It may be necessary to apply the irradiation of the rubber in several layers or, after several

Make partial fillings to achieve complete irradiation and cross-linking.

Fig. 2 shows the roughly schematic arrangement with UV irradiation facilities above and below the

Fully or partially UV-permeable mold The silicone rubber filled into the mold is exposed in such a way that its rapid cross-linking is initiated. The mold is either completely permeable to UV radiation or contains windows of UV-transparent material at suitable locations. Simultaneous irradiation In several directions it is possible to achieve a substantially complete exposure of the entire volume of the silicone rubber. A gradual irradiation is possible. Fig. 3 shows the roughly schematic arrangement with a UV irradiation device in the course of the enveloped

Material supply. There is the exposure of the

Silicone rubber in the run-up to filling. Of the

Silicone rubber is so in such a modification

that its crosslinking is suitably delayed and, after its exposure but before crosslinking, allows the mold to be filled.

4 shows the roughly schematic arrangement with a UV irradiation device in the course of the uncoated

Material supply. There is the exposure of the

Silicone rubber also in the apron .der filling. The silicone rubber is so in such a modification

that its crosslinking is suitably delayed and, after irradiation but before crosslinking, allows filling of the mold.

Claims

Claims:

1. A method for the manufacture of composite insulators, in

which a supporting component is provided with a screen of silicone rubber: characterized in that the crosslinking of the silicone rubber is initiated by UV irradiation,

2. The method of claim 1, wherein the supporting member is a rod or tube of fiber reinforced plastic.

3. The method according to claim 1 or 2, wherein the

Silicone rubber is irradiated from the open side of the mold.

4. The method of claim 1 to 3, wherein the mold is made of UV-transparent material or the mold has UV-permeable window and the silicone rubber is irradiated through the mold.

5. The method of claim 1 to 4, wherein the irradiation of the silicone rubber is carried out in a material supply for the silicone rubber to the mold and the

Silicone rubber is such that its cross-linking is retarded and, after its irradiation, allows the filling of the casting mold,

6. The method according to claim 1 to 5, wherein the

Silicone rubber has a viscosity [D = 0.9 / 25 ° C] of 1000 mPas to 20,000 mPas.

The method of claim 1 to 6, wherein the wavelength of the UV radiation is 200 to 500 nm. A method according to claims 1 to 7, wherein the

silicone rubber

(A) at least two alkenyl groups per molecule containing polyorganosiloxane having a viscosity at 25 ° C from 0.1 to 500,000 Pa-s,

(B) containing at least two SiH functions per molecule

Organosilicon compound and

(C) by light from 200 to 500 nm activatable platinum group catalyst.