CA2005978A1

CA2005978A1 - Free-flowing granular formulation

Info

Publication number: CA2005978A1
Application number: CA 2005978
Authority: CA
Inventors: Udo Fuhrmann; Heinz Schwab
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1988-12-21
Filing date: 1989-12-19
Publication date: 1990-06-21
Also published as: JPH02229863A; EP0376884A2; EP0376884A3; BR8906597A

Abstract

K-17377/=/CGW 18 Free-flowing granular formulation Abstract of the Disclosure The invention relates to a free-flowing granular formulation which is obtained by charging to a fluidised bed a finely particulate inorganic or organic filler by itself or together with a solid component of a curable mixture or a part thereof, and then spray coating the particles with a curable mixture, the other components or the remaining portion of the curable mixture, as single component system, in the form of a liquid or suspension. The formulation so obtained is preferably used as moulding or coating powder, in particular for coating electrical or electronic components.

Description

2~)~)59~3 K-17377/=/~GW 18 Free-flowin~ granular forrnulation The present invention relates to a free-flowing granular formulation consisting of an agglomerate of finely divided inorganic or organic filler particles which contain a curable mixture as single component system, the mixture components being homogeneously coated on said filler particles.

Free-flowing single component powder mixtures or single component granular forrnula-tions obtained fro~ curable epoxy resin granular forrnulations can be prepared in known manner by the dry blending or melt fusion process. In the dry blending process the individual components are either first ground separately and then - after they have the appropriate granular size - homogenised by a blending process, or they are immediately mixed together and jointly comminuted and homogenised during the grinding procedure.
In a powder mixture obtained in this manner, the individual cornponents such as resin, curing agent or curing catalyst, filler, dye and other additives, are present in the form of discrete particles, so that this mixture may be terrned heterogeneous. In the melt fusion process the substantially solid components are premixed dry in a mixing apparatus, for example in a Henschel mixer, and the blend is subsequently fused, for example in an extruder or on a two-roll mill, such that the solid and infusible mixture components are wetted very thoroughly with the melting mixture components which are dissolved in this melt. The cooled melt is then ground and sieved. The individual grains of this powder formulation contain in the core as well as on the surface a completely homogeneous mixture in the original concentration.

A free-flowing resinous product having a high concentration of inorganic ~lllers is prepared in European patent 38 292 by suspending and stirring the finely particulate ~lller together with a crystallised synthetic calcium silicate of specific size in the liquid resin or hardener. The free-flowing resin mixture obtained in Example 12 of this patent by using a liquid curable epoxy resin mixture is prepared in two steps and has a storage stability of only about one month.

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It has now been found that a granular formulation with a high concentration of filler and having enhanced processing properties, especially enhanced flow properties, is obtained by flu;dising, in a fluidised bed, a finely particulate inorganic or organic filler and spray coating the particles with a curable mixture in the form of a single component system. In addition, formulations having a particularly low content of fine dust are obtained.

Accordingly, the present invention relates to a free-flowing granular formulation comprising an agglomerate of finely divided inorganic or organic particles on to which a curable mixture is spray coated in the form of a single component system, in which curable mixture at least one mixture component is liquid at temperatures below 150C, and the mixture components are homogeneously coated on the filler particles.

The individual grains of the single component system are homogeneously coated only on the surface with the individual components of the single component system. The core of the individual grains of the agglomerate consists essentially of the filler.

The fillers which may be coated in the fluidised bed are finely particulate fillers, for example fibrous, granular or powdered fillers. Suitable finely particulate fillers are all those which can be fluidised in the fluidised bed.

Examples of organic fillers suitable for the granular formulation of this invention are natural or synthetic polymeric materials such as cellulose, preferably cotton fibres or wood flour, saturated polyesters, polyamides or melamine ureas.

Eligible inorganic fillers are, for example, quartz powder, mica, talcum, asbestos, powdered slate, kaolin, wollastonite, chalk powder, dolomite, magnesium carbonate, gypsum, barites, alumina, bentonite, silica aerosol, lithopone, titanium dioxide, carbon black, carbon fibres, graphite, metal powders, especially aluminium powder, metal oxides, glass powder, glass beads, glass ~lbres, zinc sulfide, silicon carbide, cristoballite, or a mixture of fillers. Preferred fillers for the granular formulation are inorganic fillers, especially mineral fillers such as, preferably, quartz powder, especially fused silica powder, mica, powdered slate, kaolin, wollastvnite, gypsum, barites, alumina, aluminium hydroxide, magnesium hydroxide, talcum, silica or bèntonite.

The fillers can further be treated with primers which promote the adhesion of the polymer to the filler particles. It is furthermore preferred to use those finely particulate fillers . .. . . . .
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Curable mixtures present in ~he formulations of this invention may suitably be in general those which, under the influence of ligh~, heat, hardeners, catalyst or curing accelerators, can be cured during the processing to thermosetting final products. Such mixtures are essentially self-crosslinking synthetic resins which are normally precondensates, preadducts, or a mixture of curable, i.e. crosslinkable, monomers. At least one component of the curable rnixtures will be liquid at temperatures below 150C, so that the mixture is in the forrn of a liquid or ernulsion when sprayed into the fluidised bed compartment. The curable rnixture prefereably contains at least one component which is liquid at temperatures below 150C, preferably at room temperature. The liquid component can be, for example, the resin itself or a part thereof, the hardener, the catalyst or the accelerator, as well as a reactive diluent or a processing auxiliary such as a flow control agent or mould release agent.

The following self-crosslinking plastics may be used as single component system for the preparation of the granular formulations of this invention-Phenolic plastics from aldehydes and phenols or alkylated phenols which are prepared in basic medium, aminoplasts such as urea/formaldehyde resins or melamine/forrnaldehyde resins, alkyd resins and oil-modified alkyd resins, unsaturated polyesters, preferably maleic acid derivatives, epoxy resins, preferably derivatives of bisphenol A, polyurethanes and unsaturated polyimides, preferably derivatives of C-alkylated bismaleimides.curable epoxy resin mixture will preferably be used as single component system.

Particularly suitable epoxy resins are those containing on average more than one glycidyl, ~B-methylglycidyl or 2,3-epoxycyclopentyl group attached to a hetero atom (for example sulfur, preferably oxygen or nitrogen). Such epoxy resins are preferably bis(2,3-epoxy^
cyclopentyl) ethers; diglycidyl and polyglycidyl ethers of polyhydric aliphatic alcohols such as 1,4-butanediol, or polyalkylene glycols such as polypropylene gylcols; diglycidyl or polyglycidyl ethers of cycloaliphatic polyols such as 2,2-bis(4-hydroxycyclohexyl)-propane; diglycidyl or polyglycidyl ethers of polyhydric phenols such as resorcinol, bis(p-hydroxyphenyl)methane, 2,2-bis(p-hydroxyphenyl)propane (diomethane), 2,2-bis-(4'-hydroxy-3 ' ,5 '-dibromophenyl)propane, 1,1 ,2,2-tetrakis(p-hydroxyphenyl)ethane, or condensates of phenol with ~ormaldehyde obtained under acid conditions, for example . -', ~

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phenol novolaks and cresol novolaks; bis- and poly~,~-methylglycidyl) ethers of the above listed polyhydric alcohols or polyhydric phenols; polyglycidyl esters of polybasic carbo-xylic acids such as phthalic acid, terephthalic acid, ~'I-tetrahydrophthalic acid and hexa-hydrophthalic acid; N-glycidyl derivatives of amines, amides and heterocyclic nitrogen bases such as N,N-diglycidylaniline, N,N-diglycidyltoluidine, N,N,N',N'-tetraglycidylbis-(p-aminophenyl)methane; triglycidylisocyanurate; N,N'-diglycidylethyleneurea; N,N-di-glycidyl-5,5-dimethylhydantoin, N,N'-diglycidyl-S-isopropylhydantoin; N,N'-diglycidyl-5 ,5-dimethyl-6-isopropyl-5 ,6-dihydrouracil.

Further suitable epoxy resins are prereacted adducts of such epoxy resins with hardeners, which adducts are liquid or are fusible at temperatures below 15()C. It is prefeIred to use prereacted adducts which are liquid or fusible at temperatures below 50C, most preferably the prereacted adducts which are liquid at room temperature.

The functional group containing synthetic resins may also be components of a plastics material and may be crosslinked with suitable hardeners or modified with suitable comonomers. The liquid reaction components may also be monomers for the preparation of polymers, and are for example polyepoxide compounds, polyisocyanates and ethylenically unsaturated compounds.

Suitable hardeners for epoxy resins are acid or basic compounds. Examples of suitable hardeners are typically: amines or amides such as aliphatic, cycloaliphatic or aromatic primary, secondary and tertiary amines, for example monoethanolamine, diethylenetri-amine, triethylenetetramine, trimethylhexamethylenediamine, diethylenetriamine, tri-ethylenetetramine, tetraethylenepentamine, N,N-dimethylpropylene-1,3-diamine, N,N-di-ethylene-1,3-propylenediamine, 2,2-bis(4'-aminocyclohexyl)propane, 3,5,5-trimethyl-3-(aminomethyl)cyclohexylamine (isophoronediamine), Mannich bases such as 2,4,6-tris(di-methylaminomethyl)phenol; m-phenylenediamine, p-phenylenediamine, bis(4-amino-phenyl)methane, bis(4-aminophenyl)sulfone, m-xylylenediamine; adducts of acrylonitrile or monoepoxides, such as ethylene oxide or propylene oxide, with polyalkylenepoly-amines such as diethylenetriamine or triethylenetetramine; adducts of polyamines such as diethylenetriamine or triethyltetramine, in excess, and polyepoxides such as diomethane polyglycidyl ethers; ketimines, for example from acetone or methyl ketone and bis(p-aminophenyl)methane; adducts of monophenols or polyphenols and polyamides; poly-amides, especially those from aliphatic polyamines such as diethylenetriamine or tri-ethylenetetramine, and dimerised or trimerised unsaturated fatty acids, such as dimerised . .. . ............................. .

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3~7a linseed oil fatty acid (VERSAMID(~); polymeric polysulfides (1 HIOKOL~); dicyandi-amide (1-cyanoguanidine), aniline/formaldehyde resins; polyhydric phenols, for example resorcinol, 2,2-bis(4-hydroxyphenyl)propane or phenol/formaldehyde resins; boron tri-fluoride and its complexes with organic compounds such as BF3 ether complexes and BF3 amine complexes, for example BF3 monoethylamine complex; acetoacetanilide BF3 com-plex; phosphoric acid; tr~phenylphosphite; polybasic carboxylic acids and their an-hydrides, for example phthalic anhydride, A4-tetrahydrophthalic anhydride, hexahydro-phthalic anhydride, 4-methylhexahydrophthalic anhydride, 3,6-endomethylene-~4-tetra-hydrophthalic anhydride, 4-methyl-3,6-endomethylene-~4-tetrahydrophthalic anhydride (methylnadic anhydride), 3,4,5,6,7-hexachloro-3,6-endomethylene-~4-tetrahydrophthalic anhydride, succinic anhydride, adipic anhydride, trimethyladipic anhydride, azelaic an-hydride, sebacic anhydride, maleic anhydride, decenylsuccinic anhydride, pyromellitic di-anhydride or mixtures of such anhydrides.

Compounds which are known per se may also be used as accelerators, for example:
complexes of amines, preferably tertiary amines such as monoethylamine, trimethylamine and octyldimethylene, with boron trifiuoride or boron trichloride, tertiary amines such as benzyldimethylamine, tris(dimethylaminomethyl)phenol, hexamethylenetetramine or 1,6-bis(dimethylamino)hexane; urea derivatives such as N-4-chlorophenyl-N',N'-di-methylurea(monuron), N-3-chloro-4-methylphenyl-N',N'-dimethylurea (chlorotoluron), N-(2-hydroxyphenyl)-N',N'-dimethylurea and N-(2-hydroxy-4-nitrophenyl)-N',N'-di-methylurea, unsubstituted or substituted imidazoles such as imidazole, benzimidazole, 1-methylirnidazole, 3-methylimidazole, 2-ethyl-4-methylimidazole, 2-vinylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-(2,6-dichlorobenzoyl)-2-phenyl-imidazole and 1-2,4,6-trimethylbenzoyl)-2-phenylimidazole, as well as phosphines.

Examples of suitable hardeners for polyisocyanates are liquid branched polyesters, linear polyesters, polyacetals, polyethers and polythioethers.

Examples of suitable comonomers for unsaturated polyimides are ethylenically unsaturated compounds such as styrene, acrylates or methacrylates.

The curable mixtures may further contain the customary rnodifiers such as pigments, flame retardants, antioxidants, fluorescent whitening agents, plasticisers or stabilisers against light- or heat-induced degradation.

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The granular formulation of this invention can be prepared by fluidising, in a fluidised bed, a finely particulate inorganic or inorganic filler by itself or together with a solid component of a curable rnixture or a part thereof, and then spray coating the particles with a curable mixture, the remaining components or the remaining portion of the curable mixture, as single component system, in the form of a liquid or suspension.

Hence the present invention also relates to the above described process for the prepara~ion of the granular formulation of this invention.

The curable mixture can be spray coated on to the organic or inorganic filler in any fluidised bed apparatus, for example in a fluidised bed granulator or in a spray fluidised bed granulator. The mode of operation of such apparatus is known. Fluidised beds are used, for example, for drying solutions, for recovering solids from solutions, for drying and agglomerating solids as well as for coating objects or solid parti~les with other materials (q.v. "~nlagen-Technik", CAV January, 1973).

The preparation of the granular formulation of this invention can normally be carried out at room temperature as well as at elevated temperature, i.e. in the temperature range up to ca. 100C, and is contingent, on the one hand, on the reactivity of the curable mixture and, on the other, on the condition from which temperature below 50C at least one of the mixture components is liquid. It is preferred to carry out the process of the invention in the temperature range from 25-70C.

The process of this invention thus affords the advantage that, aside from using mixture components which are liquid at room temperature, it is also possible to use low melting components, i.e. those that melt at temperatures below 50C, for the curable mixture.

The amount of the curable mixture which can be sprayed into the fluidised bed over a specific period of time - the so-called feed concentration - may vary within wide limits and depends, inter alia, on the mechanical parameters and on the process temperature. For example, in pilot batches of up to ca. 5 kg the feed concentration is usually from 10 to 100 g per minute. In production batches, the feed concentration is higher.

In accordance with the preferred composition of the granular forrnulation, organic fillers will preferably be used in the process of this invention, especially mineral fillers, and a curable epoxy resin mixture will preferably be used as curable single component system.

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The granular formulation of this invention has the advantage that it is virtually free from impurities, as its preparation in a fluidised bed granulator is substantially able to prevent abrasion of metal, ceramics or other materials.

The granular formuiation of this invention mainly finds utility as moulding, impregnating and coating powder as well as free-flowing adhesive, and is used in particular ~or coating electrical or electronic components. The granular formulation can be compressed to block material, i.e. to material which can be processed mechanically as moulding compound.

Example 1: 2025 g of quartz powder (50:50 mixture of "W 12" and "M 500" ex Quartz-Werke, D-5020 Frechen) and 37.5 g of wax (OP Wachs, ex Hoechst AG) are charged to a fluidised bed granulator (type "WSG 5" supplied by Glatt, ~-7859 Haltingen) and fluidised. Into this fluidised bed is sprayed a homogeneous mixture itl the form of a prewarmed (T = 30C) liquid reaction resin product consisting of 173 g of bisphenol A
di~lycidyl ether having an epoxide equivalent weight of 178 and a viscosity of 6 500 mPa-s, 263 g of dodecenylsuccinic anhydride and 2.6 g of a BCI3/N,N-dimethyl-N-octyl-amine adduct. The average feed concentration is 25 g/min, such that after ca. 18 minutes a dry, free-flowing granular formulation with the following properties is obtained in 99%
yield:

filler content: 78 - 83 % by weight gel time at T = 175C
(measured with a gelling time plate) 110 sec.
spiral flow length at T = 175C:1300 mm ASTM Test Method D 312/72) Example 2: 2000 g of quartz powder ("M 500", ex Quartz-Werke) and 42 g of wax (OP
Wachs, ex Hoechst AG) are charged to a fluidised bed granulator ("Type WSG 5") and fluidised. Into this fluidised bed is sprayed a liquid suspension which has been preheated to 65C. This suspension has been premixed from 836.5 g of bisphenol A diglycidyl ether having an epoxide equivalent weight of 178 and a viscosity of 6 500 rnPa-s, 54.5 g of dicyandiamide (1-cyanoguanidine) and 15.() g of chlorotoluron [3-(3-chloro-4-methyl-phenyl)-1,1-dimethylurea]. The average feed concentration is 28 g/min, such that after ca.
33 minutes a dry, free-flowing granular forrnulation with the following properties is ob-.
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tained in 99% yield:

ller content: 6~ - 70 % by weight gel time at T = 175C
(measured with a gelling time plate)110 sec.
spiral flow length at T = 175C: 1900 mm ASTM Test Method D 312/72) Example 3: 2500 g of a dry mixture consisting of 1617.65 g of barites powder ("Type 115", ex Bassermann & Co., D-6800 Mannheim) and 882.35 g of a solid epoxyresin based on bisphenol A having an epoxide equivalent weight of 740 and a softening point of T = 90-100C are charged to a fluidised bed granulator ("Type WSG S") and fluidised. Into this fluidised bed is sprayed a liquid suspension which has been preheated to 43C. This suspension is premixed from 381.2 g of bisphenol A diglycidyl ether having an epoxide equivalent weight of 178 and a viscosity of 6500 mPa s, 44.1 g of dicyandi-amide and lS.9 g of chlorotoluron. The average feed concentration is 45 g/min, such that after ca. 10 minutes a dry, free-flowing granular formulation with the following properties is obtained in 97% yield:

filler content: 53-55% by weight gelling time at T = 175C
(measured with a gelling time plate) 142 sec.

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Claims

1. A free-flowing granular formulation comprising an agglomerate of finely divided inorganic or organic particles on to which a curable mixture is spray coated in the form of a single component system, in which curable mixture at least one mixture component is liquid at temperatures below 150°C, and the mixture components are homogeneously coated on the filler particles.

2. A granular formulation according to claim 1, wherein the filler is an inorganic filler.

3. A granular formulation according to claim 1, wherein the filler is a mineral filler.

4. A granular formulation according to claim 3, wherein the mineral filler is selected from the group consisting of quartz powder, mica, powdered slate, kaolin, wollastonite, gypsum, barites, alumina, aluminium hydroxide, magnesium hydroxide, talcum, silica or bentonite.

5. A granular formulation according to claim 1, wherein the single component system is a mixture which can be cured to a thermosetting final product.

6. A granular formulation according to claim 1, wherein the single component system is a curable epoxy resin mixture.

7. A process for the preparation of a free-flowing granular formulation as claimed in claim 1, which comprises fluidising, in a fluidised bed, a finely particulate inorganic or inorganic filler by itself or together with a solid component of a curable mixture or a part thereof, and then spray coating the particles with a curable mixture, the remaining components or the remaining portion of the curable mixture, as single component system, in the form of a liquid or suspension.

8. A process according to claim 7, wherein the filler is an inorganic filler.

9. A process according to claim 7, wherein the curable single component system is a curable epoxy resin mixture.

10. A process according to claim 7, which comprises fluidising an inorganic filler and then spraying coating the particles with the curable epoxy resin mixture, as single component system, in the form of a liquid or suspension.

11. A process according to claim 7, which comprises fluidising the inorganic filler together with a solid component of the curable epoxy resin mixture, and then spray coating the particles with the other components of the curable mixture, as single com-ponent system, in the form of a liquid or suspension.

FO 7.3/STA/gb*