PT98280A - PROCESS FOR FIXING MATERIAL IN COILS AND USING POLYMERIZABLE MASSES BY RADICALS FREE FOR THIS EFFECT - Google Patents

Description

" PR0GE3SC FOR MATERIAL FIXING SM COILS AND USING BE POLYMERIZABLE MASSES BY RADICALS FREE FOR BSSE EFFECT " The present invention relates to a method for securing material in coils, in particular non-transparent coil material, such as coils of wires in electrical operating devices, such as rotors, stators and transformers, by means of impregnation ( for example, immersion or gouging) with free radical polymerizable masses, followed by thermal hardening.

Electric operating devices, such as rotors or transformers, often consist of a metal core in which a sheet or wire material is wound, for example copper foil or copper wire. In these three-dimensional parts, the coils are presently impregnated with free-radically polymerizable masses and subsequently heat-hardened at temperatures above 100øC for about one to one hundred and eighty minutes. The free radical polymerizable materials, the so-called impregnation resins, may contain, for example, unsaturated polyester resins dissolved in unsaturated aromatic or aliphatic monomers,

polymers, such as styrene and hexanediol diacrylate. Often, monomers of this type have a very high vapor pressure with the result that a large proportion of the monomers escapes during heat setting. This causes problems of pollution of the environment; the styrene-containing materials, for example, have an unpleasant odor and relatively high toxicity. The pollutants therefore have to be eliminated, for example, by combustion.

It is an object of the present invention to provide processes and impregnating agents suitable for securing three-dimensional parts comprising, for example, yarn reels, which are already in the laminated state, impregnating agents which give rise to a lower emission of volatile constituents , such as volatile monomers, in the course of heat setting.

This problem is solved according to the present invention by a fixing process in which the three-dimensional articles to be fixed are impregnated with free radical polymerizable masses and then heat hardened but in which the initial hardening of the articles is carried out. impregnated surfaces exposing them to high energy radiation between the impregnation and thermal setting processes. This can be achieved in accordance with the present invention in a particular manner by the use of free radical polymerizable masses containing free radical initiating agents, either as single compounds or as mixtures, which account for both radiation raises energy as to heat. The process according to the present invention, which includes the use according to the invention of the aforementioned free radical polymerizable materials, enables thin films to be formed on the surfaces of the three-dimensional articles impregnated by high energy radiation action. When parts which are inaccessible to high energy radiation are subsequently heat hardened, these films largely prevent the escape of the volatile constituents, in particular of the volatile monomers. The process according to the present invention is especially preferred for non-transparent winding materials which are non-permeable to radiation, such as ultraviolet radiation or electron beams.

The free radical polymerizable masses used in accordance with the present invention can be cured by both high energy radiation and heat supply, i.e. by high temperature action.

In order to achieve this, free-radically polymerizable masses which can be cured by high energy radiation (e.g., ultraviolet radiation or electron beams) or heat are used. For this purpose, it may be advantageous to activate the free radical polymerizable masses by the addition of free radical initiating agents. The radical initiators used are of the type that can be activated either by high energy radiation or by heat. In particular, it is appropriate to use blends of free radical initiators that respond to high energy radiation (photoinitiators) and respond to heat. The addition of photoinitiator agents depends to a large extent on the type of radiation used to harden the surface. Thus, the addition of photoinitiator agents is not required, for example, when the surface is hardened by electron beams *

The aforementioned starting agents of the invention, including photoinitiator agents and heat responsive initiators, are of the type conventionally used in this field.

The photoinitiator agents used, for example, may be conventional initiators which absorb in the wavelength range of from about 190 to about 1000 nanometers. Examples of such photoinitiator agents include chlorine-containing initiators such as chlorine-containing aromatics, for example, those described in U.S. Patent 4,889,815 and aromatic ketones as described in the patent of US-A-4 318 791 or in European Patents EP-A-0 003 002 and EP-A-066463 and hydroxyalkyl-phenols, as described in the patent of US-A-4 347 111 | the phosphine oxides which are described in European Patents EP-A-0,007,086, 0,007,508 and 0,304,783} the water-soluble initiating agents, for example based on hydroxyalkylphenones, as described in the patent U.S.A. 4,602,097, unsaturated initiator agents such as OH-functional aromatic compounds which have been esterified, for example with acrylic acid, as described in U.S. Patent 3,929,490 and EP-A-0 143 201 and EP-A-0 341 560) and combinations of these initiating agents as described, for example, in U.S. Patent 4,007,652. Preferred examples are 2-methoxy-2-hydroxy-propiophenone, benzophenone, thioxanthone derivatives, acylphosphine oxides and Michler's ketone,

The photoinitiator agents mentioned above may be used alone or in the form of mixtures. Combinations of phosphine oxides with other conventional photoinitiator agents, for example, are preferred.

Heat-responsive free radical initiators are also conventional initiators used in the heat cure domain of free-radically polymerizable masses.

Examples of such heat responsive initiators include labile C-C compounds, as described, for example, in German patent DE-PS-121922. These compounds are 1,2-substituted ethanes which correspond to the following general formula

R 11 is R, R 2 - c - c

X in which the symbols and represent aromatic groups; R2 is hydrogen, aliphatic or aromatic; the symbol represents an aliphatic or aromatic group; and X and Y represent an optionally blocked hydroxyl group and / or a halogen atom.

Other examples of 1,2-substituted ethanes suitable for use as initiators in free radical polymerization with heat supply are those corresponding to the following general formula:

or > In which the symbol represents a chlorine atom a group of one of the formulas -OH, -OCH2, -00.41 ,. 3 or 5 -CH2, -CN, -NH2 or -OSi (CH3) 3, as described for example by A. Bletzki et al. Krolikowski in Kunststoffe 70 (1983) 9, pages 558-562.

Other examples of 1,2-substituted ethane based thermally activated radical initiators are those corresponding to the following general formulas

And

OR 7

C = 0 G = Q

W

In which the groups represented by the symbol may consist independently of each other in hydrogen atoms or one or more alkyl groups or one or more alkoxy groups such as methyl or methoxy groups; and the symbols may independently represent hydrogen atoms or alkyl groups, for example with one to four carbon atoms, for example methyl groups or ethyl groups.

Compounds of this type are described, for example, by H. ¥ olfers in Kunststoffe 68 (1978) 9, pages 553-555 by D. Braun in Kunststoffe 69 (1979) 2, pages 100-101. These compounds are commercially available primers. A further group of initiators for ra-

are the cyclic silyl-pinacol esters bifunctional initiators, as described, for example, in Polym. Bull. Ló, 95 (1986).

As already mentioned for the photoinitiator agents, the thermally activated initiators can also be used in the form of mixtures.

As starting agents, conventional peroxides and azide compounds can also be used. Compounds of this type are known as photoinitiator agents and / or as thermally labile initiating agents. The peroxides and the initiators based on azetic compounds may therefore be used in themselves as long as they are sufficiently active as photoinitiator agents or as heat activated initiators. They may also be used as mixtures with photoinitiator agents or thermally labile initiators.

Examples of suitable peroxides include organic peroxides of the genus conventionally used, for example, as free radical initiators in the plastics industry, such as di-t-butyl peroxide, dibenzoyl peroxide, poroxy dicarboxylic acids such as peroxy- acetic acid, peroxy-dicarbonates, such as di-sec-butyl peroxy-dicarbonate, peroxy-diesters, such as tertiary butyl per-ester, 2-ethylhexanoic acid,

Wr hydroperoxides, such as cumene peroxide and ketone peroxides, such as methyl ethyl ketone peroxide. Azo bis-isobutyronitrile is an example of the azo initiator and can be used primarily as a thermally activatable initiator.

According to the present invention, it is suitable to use mixtures of photoinitiator agents and thermally activatable initiators. The initiators are used in the amounts conventionally employed for photoinitiator agents and heat-responsive initiators. The total amount of initiators used may range, for example, from 0.01 to 20% by weight, preferably from 0.1 to 10% by weight, more preferably from 0.1 to 5% by weight based on total mass. There is no limit to the maximum quantity that may be added but the amount is kept so as to be as low as possible for economic reasons. The quantitative ratios of photoinitiator to thermally labile initiating agent may vary between distant limits and may range, for example, from 1: 1 to 20: 1, preferably from 1: 1 to 10: 1, and conversely.

The masses of impregnation resins used may be free radical polymerizable masses well known to those skilled in the art,

polymerizable by free radicals. They may be monomers, oligomers, polymers or copolymers.

Examples of free radical polymerizable masses include conventional masses which can be radiation hardened, in particular UV curable masses based on monomers, oligomers, polymers, copolymers or combinations thereof having one or more olefinic double bonds, such as, for example, acrylic acid esters and methacrylic acid esters and compounds having one or more vinyl or allylic double bonds. Examples of monofunctional monomers are butyl (meth) acrylate and hydroxyethyl (meth) acrylate; examples of bifunctional monomers are hexanediol di- (meth) acrylate and dipropylene glycol di (meth) acrylate Examples of trifunctional and tetrafunctional monomers are trimethylol propane tri- (meth) acrylate and tri- or tetra- ) pentarithritol acrylate. The term " (meth) acrylate " Examples of vinyl-unsaturated monomers include styrene and styrene derivatives such as divinyl benzene, p-methylstyrene and vinyl toluene. Examples of allyl compounds are diallyl phthalate and tri-allyl esters and pentaerythritol tetra-allyl. Examples of oligomers and prepolymers are: (meth) acryl functional acrylic (meth) acrylates, epoxy resin (meth) acrylates, for example the reaction products of 2 moles of (meth) acrylic acid with commercial epoxy resins, such as 12 W-

(Meth) acrylates, poly (meth) acrylates, urethane (inet) acrylates, amine (meth) acrylates, unsaturated polyesters, unsaturated polyurethanes, silicone (meth) acrylates and combinations thereof . Examples of such curable products are described in the following documents (epoxide) (meth) acrylates in European Patents EP-A-0 333 896 and EP-A-0 049 992 and in U3-A-4 485 123; (meth) acrylates in European patents EP-A-053 749 and EP-A-0 209 684 and in U.S. Patent 4,162,274; (meth) acrylates in European Patent EP-A-0,883,666 and in German Patents ΌΕ-Λ-38 10 140 and DE-A-38 20 294.

Free radical polymerizable masses containing olefinically unsaturated polyesters and containing olefinically unsaturated monomers as reactive diluents are particularly suitable for the process according to the present invention. These monomers may be mono-unsaturated or polyunsaturated. Examples of these monomers include those mentioned above. Acryloxy compounds and / or racemicryloxyl compounds are suitable. Particularly preferred are hexanediol diacrylate and butanediol diacrylate as examples of such reactive diluents; they may be used alone or in the form of mixtures together with the unsaturated polyesters. - 13

Styrene and vinyl toluene are further examples of racemers suitably used with olefinically unsaturated polyesters. Examples of impregnation resin masses based on olefinically unsaturated polyesters containing monomers as reactive diluents are mentioned in EP-A-0 5 3

The unsaturated polyesters used may be polyester resins known for this purpose, in particular the so-called imide-containing unsaturated polyesters described in German Offenlegungsschrift DE-A-15 70 273, 17 70 386 and 28 56 050. They may also the so-called imide-free polyesters which have been known for decades. These unsaturated polyesters are condensation products of polyfunctional carboxylic acids, polyfunctional alcohols and, if they are of the imide-containing type, compounds containing amino groups, optionally with a proportion of monofunctional compounds.

Examples of the polyfunctional carboxylic acids include dicarboxylic acids, such as maleic acid and fumaric acid, citracánico acid and itacenic acid, optionally mixed with saturated or aromatic carboxylic acids, such as succinic acid or adipic acid, phthalic acid, isophthalic acid, terephthalic acid and tetrahydrophthalic acid, endomethylene-tetrahydrophthalic acid and the corresponding partially or completely halo-substituted compounds (for the propagation delay properties of - Ih -

flames). Examples of compounds containing different functional groups are citric acid, monoethanolamine, aminoethane carboxylic acid and the corresponding amino-alcohols or amino carboxylic acids containing three or four CHO groups. These acids may be used in the form of esters, semi-esters or anhydrides.

Compounds which contain hydroxyl groups may also be compounds used in the art for the preparation of polyesters. Suitable diols are, for example, glycol, neopentyl glycol and propylene glycol. Examples of polyesters having three or four hydroxyl groups include gliolol, trimethylolpropane, trimethylol ethane, pentaerythritol, dipentaerythritol and tris-ethylisocyanurate.

The imide-containing unsaturated polyesters advantageously contain tetrahydrophthalic acid or its anhydride incorporated by condensation to form a pentane-containing imide ring containing amino groups. The polyesters may contain monofunctional carboxylic acids, alcohols and / or amines as chain breaking agents. They may also contain saturated and unsaturated oils, for example, hydroxy-functional oils, such as castor oil, or carboxy-functional oils, such as maleate oils.

For the preparation of the free radical polymerizable masses used in accordance with the present invention,

In the invention, the aforementioned masses are mixed with the free radical initiating agents, in particular with the mixture of photoinitiators and thermally activatable initiators. Free radical polymerizable materials may furthermore contain conventional additives, such as pigments, solid diluents, plasticizing components, accelerating agents (for example, metal salts, substituted amines) and stabilizing agents (for example, hydroquinone, benzoquinone), as is commonly used in this domain. The masses are solvent-free.

The free-radically polymerizable masses can be used, for example, by performing the following for the impregnation of wounded materials to be stabilized, for example wire coils: - by dip-impregnation: when this process is employed, the material the impregnation is dipped in the impregnation resin for a predetermined period of time, for example by means of preliminary tests or can be continuously passed through the impregnation resin. By vacuum impregnation: When employing this process, the material to be impregnated is first vacuum-treated in a vacuum tank. When the desired vacuum is reached, the impregnation agent is introduced into the vessel under vacuum from a storage tank. By drip impregnation: this process is preferred. In this case, the objects are not dipped in the impregnating agent but the polymerizable mass is applied to the substrate from the injectors. The substrate may, for example, be rotated at the same time. To ensure careful penetration, it may be advantageous to pre-heat the objects to which the impregnation mass is to be applied, but in order to avoid premature gelling, the temperature at which the objects are preheated should not exceed the temperature of hardening of the polymerizable masses.

After impregnation, the free radical polymerizable mass is cured on the surface of the substrate to be fixed using a light source emitting high energy radiation, for example an ultraviolet light source or an electrode radiation source. Suitable sources of radiation may be the conventional sources used for the radiation of ultraviolet beams or electron beams. Appropriate sources of ultraviolet radiation are mercury irradiation lamps under high pressure and mercury under medium pressure. W-

The impregnated three-dimensional objects move in front of the radiation source so that the radiation causing the hardening occurs on its surface, so that a series process can be employed '

For example, the object may be rotated when moving in front of the radiation source in order to ensure uniform absorption of the radiation. The treatment with high energy radiation hardens the resin layer on the surface of the article to be fixed so that to a great extent the escape of volatile constituents such as volatile monomers during the subsequent heat treatment feet is avoided. It has been discovered by the applicant that the formation of even very thin layers on the surface prevents emissions during the subsequent feet-heat setting. It has been found in practice that layers with thicknesses of, for example, about 1 micrometer are sufficient to provide a substantial reduction of emissions. The Applicant has also surprisingly found that surface layers of any thickness can develop without causing deleterious effects on subsequent heat treatment . Layer thicknesses suitable for the practical purposes may be achieved within short reaction times corresponding to the set times used for ultraviolet curing 18 -

or with electron beam. Subsequent hardening is carried out by means of a subsequent heat treatment, which can also be carried out in series. This hardening is carried out by means of conventional heat hardening equipment, such as hardening greenhouses or by irradiation with infrared rays. Temperatures may range, for example, within the range of about 80Â ° to 180Â ° C, with reaction times ranging, for example, from 1 to 180 minutes, depending on the system to be cured. The typical serial process is shown in the attached Figure. The impregnated coil material is transported in a rotational motion so as to pass in front of the high energy radiation source and thereafter through a thermal curing device. The process according to the present invention may be used to fix coiled materials, but in principle is also applicable to other substrates which need to be fixed by heat setting. The process according to the present invention is particularly suitable for securing wire coils, in particular for securing electric coils used in electrical operating devices, such as rotors, stators,

mers, etc. In addition, the process according to the present invention may be used to fix winding material containing metal films, such as copper films as used in the electric industry. Another application is the attachment of winding material based on glass fibers, synthetic resin fibers and synthetic resin films. The process according to the present invention largely prevents the emission of volatile monomers rapidly forming an outer polymer layer. In this way the consumption of material is very greatly reduced without loss of the impregnation quality and an improved impregnation quality is obtained for consumption of material. The process results in greater economy and / or longer service life of the material wound under thermomechanical demands. A particular advantage of the process according to the present invention is that it can be carried out in a serial process or continuously.

EXAMPLE

A solution of a mixture of polyester of isophthalic acid and an imide polyester (prepared according to EP-A-0 134 513) is prepared according to the following composition,

styrene. The solution is added with a heat-responsive initiator and a photoinitiator agent to 50 parts (by weight) of unsaturated imide polyester, 50 parts of polyester of unsaturated isophthalic acid, 77 parts of styrene, , 5 parts of hydroquinone (stabilizing agent), 5 parts of phenyl-ethene derivative (heat-responsive initiator according to German patent DE-A-121922b), 5 parts of photoinitiator (Darocu ^ H73 from Merck).

Copper wire coils of a rotor (diameter = 5 centimeters) are impregnated with the solution mentioned above. They are animated by rotating motion and passed through a source of UV radiation (three mercury irradiation lamps under high pressure, 100 w / cm) at a speed of 5 meters per minute.

A thin polymer film (10 to 3000 micrometers) is obtained on the surface. The rotor is then rotated and passed through an oven heated at 150 ° C for fifteen minutes. 21 U ·

Thus, the remaining impregnation solution is hardened within the rotor.

By first forming the polymer layer on the surface, the emissions of volatile monomers are drastically reduced, as can be seen in the following table:

Impregnation and hardening without ultraviolet radiation 16

Impregnation, ultraviolet hardening and heating (invention) .2

Emission in percentage by weight of the total impregnation resin

Reduction of the emission in percentage 0 88

Similar results are achieved if the styrene of the recipe mentioned above is replaced by vinyl toluene, dipropylene glycol diacrylate, trimethylol propane triacrylate or pentaerythritol tri- (or tetra) acrylate; and if the mixture of this Example described above is mixed with 50 parts by weight of unsaturated epoxy-acrylate, an unsaturated urethane acrylate or a polyester-acrylate.

Claims (7)

1 A process for fixing material in coils by impregnating the material already into coils with free radical polymerizable masses followed by thermal curing, characterized in that, between impregnation and thermal hardening, the exposed surface of the impregnated coil material is hardened by high energy radiation. 2. A process according to claim 1, wherein the free radical polymerizable mass used for the hardening comprises free radical initiators which respond to both high energy radiation and the heat supply. 2 3. A process according to claim 2, wherein the free radical polymerizable mass used for the hardening contains mixtures of free radical initiators that respond to high energy radiation, are free radical initiators which respond to the heat. 4. A process according to any one of claims 1 to 3, characterized in that the hardening of the surface is carried out with ultraviolet radiation or with bundles of electrodes. 5. A process according to any one of claims 1 to 4, characterized in that the materials in coils which are fixed are coils of non-transparent materials. 6. A method as claimed in claim 5, wherein the materials are fixed in coils of electrically conductive wires or fibers of non-transparent polymers. 7.- Process according to. any one of claims 1 to 6, characterized in that it is carried out sequentially by transporting the materials in coils impregnated in rotation by a source of radiation and then by means of a device for heat treatment. ϋ duswi < v Property Agent SUMMARY METHOD FOR FIXING MATERIAL ON COILS AND USING POLYMERIZABLE MASS BY RADICALS FREE FOR THAT EFFECT "A process is described for the attachment of material to coils. Coils were fixed by impregnation with free-radically polymerizable masses followed by thermal hardening. Emissions occurring during thermal setting should be avoided. In the fastening process the exposed surface of the impregnated coils is partially hardened by high energy radiation between the impregnation operation and the heat setting operation of the free radical polymerizable mass. Application in the fixing of electric coils. The Official Agent of Industrial Property