CA2015476C - Product for lubricating carbon fibres for a composite material and process for producing the said material - Google Patents

Abstract

According to the invention, the reactive lubricating product of carbon fibres for embedding in a resin which can be hardened by X or beta radiation according to a radical mechanism is constituted by a monomer having at least one functional group (F1) able to form a covalent chemical bond with the hydroxyl sites of the carbon fibres and an ethylene unsaturation (F2) able to crosslink with the resin during its hardening under irradiation.

Description

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P1~DUCI' FoR LUBRICATII~ CARHON FIBRES FUR A CQ~POSITE MATERIAL
AI~ PROS FOR PF~DiICING SAID MATERIAL
T1G~~l'1?TDT' TllA7 The present invention relates to a product for lubricating carbon fibres for embedding in a resin hardenable by radiation in accordance with a radical mechanism, which serves as an interface between the fibres and the resin of a site material. It also relates to a process for producing a ccr~osite material having lubricated fibres, as well as to the material obtained.
The carQosite mater_als can be of a simple or canplPx nature and are in particular used in the motor vehicle, aeronautical, space, navi-gation and similar fields. In the aezronautical and space field, they are more particularly used for producing engines, floor plates and leading edges of aircraft.
Fig. 1 diagrammatically shags a simple structure composite material.
Sari canposite material has carbon fibres 2 embedde3 in a matrix 4 constituted by a polymerized and/or crosslinked resin. It is also possible to see the interfaces 6 between the fibres 2 and the matrix 4.
In such a car~osite material there are two mechanical stressing types, one being longitudinal and corresponding to the direction of the fibres, as represented by arrows fl, whilst the other is transverse and perpendicular to the fibres and is represented by arxro~ws f2.
Transverse stresses are those of the shear and/or cxmpressive type.
These stresses have repercussions at the fibre-matrix interfaces 6 and in the case where the latter constitute the weak point of the ca~osite material, the mechanical perforn~ance characteristics obtained are lager than those of the matrix. In addition, when said canposite materials are subject to shear stresses, there is generally a delamin-ation between the fibres and the matrix, which can lead to the frac-ture of the material. The same applies with regards to carq~lex structure ca~posite materials, which essentially differ by the SP 5552.69 LC

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_ 2 _ presence of metal inserts or objects.
In order to obviate these disadvantages, a certain number of inter-face products deposited on the carbon fibre have been envisaged ~d which are called lubricating or sizing products for the purpose of facilitating the impregnation conditions of the fibres by the resin during the production of the carposite material and with a view to obtaining a "fastening" between the matrix and the fibres.
The known lubricating materials are generally complex copolymers or polymers leading to often long and tedious lubricating processes.
Polymeric lubricating materials are in particular described in FR-A-2 129 905, FR-A-2 129 906, FR-A-2 558 842 and FR-A-2 483 395.
More specifically, the prc-sent invention relates to a pmduct for lubricating carbai fibres for ding in a resin which, according to a radical mechanism, can be hardened by radiation not causing any 1,5 temperature rise in the material, such as X or beta radiation. Thus, the composite materials produced from resins which are polymerized and/or csrossllnked by cold ionizing rays, according to a radical mechanian, have under certain stresses, mechanical perforniance charac-teristics equal or superior to those polymerized by the thermal procedure. The production of high performance canposite materials with a single or carplex stmcture and using X or beta radiation has in particular been described in FR-A-2 564 029. However, the presently known lubricating materials are nGt car~patible with a process for hazdening resin by ionizing rays, according to a radical mechanism, a~ theY t~ l~ to inadequate interface bonds in the case of severe transverse stresses.
'Thus, the most widely used high performance or stnictural carq~osite materials (mechanical properties) are obtained by theanal polymeriz-ation and/or czrosalinking in the presence or absence of a hardener, 3p cf. the aforementioned documents.
The resins used are then epoxy resins or polyesters and the fibres SP 5552.69 LC

~0~..,~~,4'~s are carbon or ararnide glass fibres, whereof the surface preparation or lubricating material is car~patible with the thermal process used for hardening these resins.
Reference can be made in this ccnnection to US-A-3 398 210, which refers to the lubricating of glass fibres for embedding in a polyester resin with ethylena unsaturations and which can be hard~ed thernially or by irradiation. The fastening or attacYment of the lubricating product to the fibres is ensured by physical bonds of the hydrogen type between silanol groups Si-0H of the fibres and those of the ~bricating products, which are products obtained by the hydrolysis of silane derivatives.
Reference can also be made to Wt0-A-85/04200 concerning the prepar-ation of cellulose fibres for anbedding in a thermally hardenable, unsaturated or non-unsaturated resin. The coating of the fibres by this preparation is followed by a hot alkaline treatment. This takes a long time, is tedious and relatively complex.
Reference can also be made to EP-A-256 852 concerning the lubricating of carbon fibres by a dimethacrylate-urethane product and which are to be embedded in a thermally hardenable, unsaturated resin.
The attachment of the lubricating pmduct to the fibres is brought about solely by Physical bonds, the polar urethane functions having affinities with the reaction sites of the fibres.
The invention also aims at improving the transverse stress character-istics of a carbon fibre canposite material, whereof the matrix is °btained by Polymerizing a resin under radiation, according to a radical mechanimn, so as to have identical perforrnance characteristics to the thermally polymerized canposite material, with regards to the compression and shear strength. The imprwemen t to these character-istics involves the use of a specific, radiation-sensitive lubricating product. In addition, lubrication must be relatively simple and industrially usable.
SP 5552.69 L~

~o~.s~~6 The invention more specifically relates to a reactive carbon fibre lubricating product having oFi reaction sites and for embedding in a .
resin cold haxdenable by radiation in accordance with a radical mechanism and constituted by a monomer having at least one functional gxnup able to thermally four covalent chenical bonds with these reaction sites and at least one second functional group differing fran the first and able to form covalent chemical bonds with said resin during its hardening under said radiation, the first group being chosen fran among isocyanate, carboxylic acid anhydride, methylol and c~xYlic acid chloride groups.
The term lubricating is understood to mean the operation consisting of coating the non-surface treated fibres with an accurately metered material quantity. Generally, this quantity represents 0.3 to 1.5%
by weight and preferably 0.3 to 0.9% by weight of the fibres.
The bifunctional lubricating product according to the invention makes it possible to assure a "windability" of the fibres at the time of impregnation by the resin, as well as a good interface quality between the fibre and the matrix (in order to have a good resistance to trans-verse stresses). The term "windability" is understood to mean that the fibre retains its shape and does not undergo fibre separation.
The first functional group F1 of the lubricating product acco~iing to the invention ensures a cavalen t chanical bond between the chanical reaction sites of the fibres and the lubricating product.
The reaction sites of the fibres are dependent rn the nature of the latter, as well as the heat treatments perforn~ed an then during their production. Thus, the reaction sites of the presently known carbon fibres are CH, N2t-!, R~=0 with R and R'=H or an alkyl, aryl or phenyl group, R' The invention solely relates to carbon fibres having mainly CH sites ~ ~ reaction sites.
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The first functional groups of the lubricating material according to the invention have the advantage of thermally forming chemical bonds with the CH sites, at tarperatures which do not trigger a txxnopolymer-ization chemical reaction of the second grr~up of the habricating product. The choice of the reaction sites present in.a larger quantity on the fibres is aimed at improving the attachment of the resin matrix to the fibres.
The functional grips of the carboxylic acid anhydride type can result fran a mono-di or tri-carboxylic acid. Preferably, the isocyanate ~Ction is used for the first group. Under these conditions, the covalent chemical bond established with the CH sites of the fibres is a urethane bond.
The second functional group F2 of the lubricating product according to the invention favours the connection between said interface product and the resin of the ornposite material matrix. This connection or bond is a covalent chgnical bond and is ensured during the cold polymerization and/or crosslinking of the ream of the oanposite material under radiation according to a radical mechanism. In particular, the second functional group must be able to copolymerize, according to a radical mechanism, with the resin of the matrix during its tsazdening and wider beta or X radiation. The second functional gsroup must also be of the same nature as that constituting the resin of the carposite material.
In order to obtain high performance carposite materials, preference ~ 91v~ to the use of resins with ethylene unsaturations such as epoxy, polyester or polyurethane resins with (meth)acrylic teirninations or mixtures of these resins. It should be noted that epoxy resins with ethylene unsaturations are resins having an epoxy origin having no longer any epoxy function. Moreover, the F2 gxnup of the lubri-cating product according to the invention is advantageously chosen without ethylene unsaturations. However, it is possible to use F2 groups of the maleimide type for resins of the bisrnaleimide type.
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~C1~~'~~6 In particular, sail second group F2 is of formula (I) ~\
C=C
R2 / \ R4 _ in which R5 represents a hydrogen star, a benzene nucleus, -C~I~ and O
R2 represents a hydrogen star or -~Oi~, with F~ representing a straight or branched aryl or alkyl radical having 1 to 12 carbon stars, R3 represents a hydrogen star or the methyl radical and R4 an aryl radical, (-0-, r-l~i_, ~_.

The aryl groups are in particular of the phenyl, naphthyl, etc. types.
The lubricating material according to the invention serves to impr~ave the adhesion of the carbon fibres to the resin matrix of a composite material. The invention also relates to a opposite material having caxbon fibres enbedded in a resin hardened by beta or X radiation accoxriing to a radical mechanism and having a reactive fibre lubri-cating product of the type defined hereinbefore. ThQ invention also relates to a process for producing sair3 canposite material.
According to an essential feature of the sail process, the latter comprises the following stages:
a) dissolving the aforsnentiored lubricating product in an organic solvent:
b) depositing the solution obtained in a) on the fibres;
c) heating the fibres obtained in b) in order to evaporate the solvent and solely trigger the chemical reaction between the first group and the reaction sites of the fibres;
d) irrQregnating the fibres obtained in c) with a resin hardenable by SP 5552.59 LC

~s~.~~°~s _ 7 _ radiation according to a radical mechanism and e) subjecting the impregnated resin fibres to said radiation in order to copolymerize the lubricating product with the resin via the second group and ha~i~ the said resin.
The functions F2 canpatible with matrixes hardenable by radiation are generally terrgerature-sensitive. Thus, stage c) of the px~xess must be carried out at a ter~erature not permitting the homopolymerizatiora of the lubricating pnxluct via the second functional group. It is also preferable to use as the organic solvent, solvents having a low v~o~ Pressure or tension Pv and a low boiling point Te. In partic-ular, the organic solvent must have a boiling point below 100°C and a vapour t~sion above 95 rob (9.5 kPa) at 20°C.
For example, the solvent is constituted by dichloranethane Pv=45.3 kPa, Te=40°C), chlox~ofonn (Pv=21 kPa, Te=60°C), tetrahydrofuran (Pv=20 kPa, Te=66°C), acetone (Pv=23.3 kPa, Te=56.5°C), Dichloroethane (Pv=24 kPa, T~83°C), methyl ethyl ketone (Pv=10.5 kPa, Te=79.6°C) or ethyl acetate (Pv=9.5 kPa, Te=77°C).
Moreover, the temperature designated T1 during stage c) is depend~t rn the reaction, designated R1, between the OH reaction sites of the fibres and the functional group F1 (and therefore the function F1), as well as the reaction between the functional groups F2 of the lubricating product.
For example, for a function F1 of the isocyanate type and a function F2 of the (meth)acrylate type (CH2=CY-COZ- with Y=H or CH3), a reaction temperature T1 of approximately 60°C is used, bearing in mind that the (meth)acrylate function is very temperature-sensitive. Under these terr~erature conditions, the duration of stage c) will obviously be sufficiently long to sure a sufficiently high reaction level R1.
By only replacing the funct:lon F2 (meth)acrylate by a cinnamate 3p function (Ph-CH=CH-002-) maleate function or fumarate function ( HO O-Cti=C'~~1~-0 ) , or by a styrene function ( CH2=CH-Ph- ) , with pH
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_8_ representing the phenyl radical, it is possible to increase the tgrQer-ature T1 to approximately 110°C. Under these conditions, at the end of stage c), the reaction level R1 is higher in the case of the (meth)acrylate function on leaving the resin impregnation chain.
The other types of functions F1 which can be used, whilst retaining the function F2 (meth)acrylate are carboxylic acid anhydride, acid chloride and N-methylol.
In the same way, it is possible to carbine these new functions F1 by replacing the function F2 (meth)acrylate by a cinnanate, maleate, fumarate or styrene function. In this case, the reaction terr~erature T1 can be chosen between 60 and 110°C.
As the lubricating product having as the function F1 an acid anhydride and as the function F2 an ethylene unsaturation, reference can be made to maleic anhydride of formula 0=C~1=CH-C=0.
As the lubricating product having as the function F1 an acid chloride and as the function F2 an ethylene unsaturation, reference can be made to the cynnanoyl chloride of forn~ula:

Ph-CHmCti-C \

As the lubricating product having as the function F1 a N-methylol and as the function F2 an ethylene unsaturation, reference can be made to the N~nethylol acrylamide of fornnala OHCH -NH-C-Ct1=CH .

In order to favour and/or accelerate the chemical reaction Rl betwe~
the reaction sites of the fibres and the first functional group to an even greater extent, it is possible to add a catalyst or a catalyst mixture to the solution centaining the lubricating product. It is also possible to add to the lubricating product solution an inhibitor of the hanopolymerization reaction between the functions F2 of the SP 5552.69 LC

201 a4'7fi lubricating product.
When the first functional group is the isocyanate group, the catalyst is constituted by DBTDL (dibutyl tin dilaurate) optionally associated with DAHO~ (1,4-diazobicyclo(2,2,2)-octane).
The lubricating product according to the invention e.g. has the following forn~ula ( II ) R5 ~ R3 C=C
R2 R4 - Ax- (~)y - Bz - F1 li with x, y and z representing 0 or 1, F1 representing -N=C=0, -C1, -CH OH, -C-C1, R5, R2, R3 and R4 having the sane meanings as herein-2 t.

before, A representing a straight or branched alkyl radical with 1 to 12 carbon atone and B representing a straight or branched alkyl radical with 1 to 6 carbon atoms or an aryl radical of type:
v O ~ 0 - ~3 ~ O -~ 4'13r O --1712-Other features and advantages of the invention can be gathered fnxn the follcxNing description given in an illustrative and non-limitative manner with reference to the attached figs. 2 to 4, fig. 1 having already been described.
Figs. 2 to 4 are block diagrams illustrating the process for producing a canposite material iron carbon fibres lubricated with the lubricating product according to the invention. Fig. 3 diagrammatically represents the lubricating of a carbon fibre with the lubricating product accor-ding to the invention.
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20154'6 -lo-With reference to figs. 2 and 3, a description is given hereinafter of the pxnduction of a carposite material part having fibres lubri-cated in accordance with the invention and anbedded in a radiation-hardened matrix. Lubrication is carried out on untreated,carbon fibres, which have undergone no surface treatment. The use of untreated fibres is symbolized by block 10 in fig. 2.
Firstly the surface state of the untreated fibres is investigated by the knaan electron spectroscopy ESCA. This stage is represented by block 12 in fig. 2. It makes it possible to deternzine the reaction sites of the fibres. With a view to an optimum fastening'of the lubricating product, the statistically most numerous reaction sites are chosen. In the case of carbon fibres of the intermediate modulus type, it is found that the preponderant reaction sites are hydroxyl groups.
This is followed by the determination of the ctnice of lubricating product, as symbolized by block 14 in fig. 2. The chosen lubricating psbduct is obviously a function of the reaction sites determined by the ESCA method, but also the resin type used for forming the matrix of the canposite material. The lubricating products are as defined hereinbefore.
The chosen lubricating product is then dissolved in an organic solvent with a low vapour tension in proportions permitting a lubricating rate of 0.3 to 2%. The solvent is necessary for aiding the distri-bution and impregnation of the fibres by the lubricating product, taking account of the sought low final lubricating level percentage.
In order to optimize the reaction R1 between the reaction sites of the fibres and the function F1 of the lubricating product, it is possible to add to the lubricating solution one or more catalysts of the reaction R1, as well as an inhibitor of the har~opolymerization action between the functions F2 of the lubricating product.
The fol7.owing stage of the product represented by block 16 in fig. 2 SP 5552.69 LC

2~l.,.r"~~"'J6 consists of depositing the lubricating solution obtained on the untreated fibres. As represented in fig. 3, this deposition takes place by passing at constant speed each fibre 18 to be lubricata3 into a tank 20 ccxitaining the lubricating solution. After passing into a spinning nozzle 22, the lubricated fibre 18 enters an oven 24 raised to the maxirn~n temperature T1 allowed for the function F2.
The passage of each fabre into oven 24 makes it possible to evaporate the solvent fran the lubricating solution, as well as to trigger the chemical reaction R1 between the function F1 of the lubricating pro-duct and the reaction sites of the fibre. This stage is represented by block 26 in fig. 2.
The tE<rperature T1 is chosen so as to aid the reaction R1 without bringing about any reaction by t~arx~polymerization of the function F2 of the lubricating pxnduct to be fasteners to the resin of the matrix.
The spinning nozzle 22 makes it possible to improve the lubricating product percentage on the fibres 18, as well as the core irnpregnation of the fibres by the lubricating product.
The storing time of each impregnated fibre is dependent on the maxim~,nn temperature T1 authorized by the function F2, the travel speed of the fibre and the length of oven 24. For example, the txavel speed is 24 m/min and the passage length in an oven 6 rn.
The fibre lubricating process 21 is then finished. The thus lubri-cated fibres 18 can be stored for several days until a given ca~site material part is manufactured.
The lubricated fibres are then impregnated in an impregnation bath by a liquid resin of the urethane-acrylic, epoxy-acrylic or polyester-acrylic type, or a fozmulation obtained by mixing these different resins. This impregnation stage is perforn~ed in known manner and is symbolized by block 28 in fig. 2.
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20.54'76 The resin-impregnated, lubricated fibres are the deposited on a support of a mandrel type representing the shape of the car~osite material part to be produced, in accordance with previously calculated winding trajectories. Winding is carried out on several layers, so as to obtain optimum mechanical performance characteristics. This winding stage constitutes the production stage of the fibrous substrate of canposite material and is symbolized by block 30 in fig. 2. In place of winding the fibres, it is also possible to carry out weaving in two or three directions.
The final stage of the process symbolized by block 32 in fig. 2 consists of polymerizing and/or cirosslinking floe resin of the matrix and reacting the function F2 with the resin of the matrix by subjecting the substrate to ionizing X or beta radiation.
The irradiation conditions for a ccr~osite material part are dependent on its shape, as well as the nature of the resin constituting the matrix. These crnditions are in particular as given in FR-A-2 564 029.
In the case of a cylindrical part, is exposed to the action under an electron or X-ray accelerator, which is moving and rotating in such a way that all the portions liable to be modified by the radiation 2p receive the minimum dose necessary for the same. These atn.~ctural modifications are obviously the copolymerization of the lubricating ps~oduct with the resin of the matrix, as well as the hard~ing of said resin. Moreover, the ccmposite material parts, pax-ticularly of the aircraft engine type, have adhesive portions for ensuring the various ~s ~ ~~tions which must be hardened by radiation. The adhesive is generally based rn an acrylic-epoxy resin.
For a canposite material part produced with carbon fibres lubricated with a lubricating product, whose function F2 is an ethyl~e unsatur-ation and impregnated with epoxy resin with an acrylic termination, use is made of an irradiation dose of SO kGy for the polymerization of the resin of the matrix and the copolymerization of the function SP 5552,69 >~

2ozs4~s F2 with the resin of the matrix.
Irradiation is ensured by X-rays or electrons, as a function of the thickness of the part in question.
In the case of a very reactive matrix resin requiring low radiation doses, e.g. approximately ZO kGy, it is necessary to choose as the minimum dose that necessary for ensuring the reaction F2 if said dose exceeds that necessary for the han3ening of the matrix.
The composite material (C.M.) part symbolized by the block 34 in fig. 2 is then finfished.
Fbr the production of a ca~osite material part, it is possible to reverse the stages of lubrication, producing the substrate and impreg-nating the fibrous substrate by the resin and this is represented in fig. 4. In particular, it is possible to carry out a weaving 30a of the untreated ffibres 10 (left-hand part of ffig. 4) prior to the ~~~t~ ~~f. The lubrication represented by block 21a is then carried out as previously.
The lubricated fibres are then impregnated by the liquid resin of the matrix, as symbolized by block 28a. The production of the ca~osite material 34a continues by irradiating the lubricated, impregnated substrate.
It is also possible to carry out the lubrication of the fibres, represented by block 21b in the right-hand part of fig. 4, just prior to the production of the fibrous substrate by weaving or winding, as represented by block 30b. The lubricated substrate can then be ~~ated by the liquid resin of the matrix, as indicated by block 28b, followed by irradiation, in order to obtain the ffinal camposite material product 34b.
Various examples of lubricating products according to the invention will now be given.
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- 14 - 20154'76 f~ca~le 1 This example relates to a product for lubricating carbon fibres having hydroxyl sites for embedding in an epoxy resin, polyester or poly-urethane having (meth)acxylic teiminations. The first functional group is an isocyanate group and the second function gnxip a methacrylate.
The fornulas of the compounds used for the production of said lubri-cating pxnduct, as well as the reaction diagram are given in appendix I.
Operating Conditions A wise addition takes place of 144 g (1 mole) of 2-hydroxypropyl methaczylate (III) to a solution containing 174 g of a mixture of 2,4 and 2,6-toluylene diisocyanate (80/20) (IV) and 0.3 g of dibutyl tin dilaurate (DBTDL) (catalyst of the alcohol-isocyanate reaction) in 300 g of anhydrous toluene, at a temperature of 60°C and under dzy nitrogen bubbling.
In order to prevent the polymerization of the double bond, 100 ppm of hydroquinone are added and stirring is continued and the temper-ature maintained at 60°C far 5 hours. This is followed by the evapor-atian of the solvent with the Rotavapor under 2.7 kPa (20 mmHg) at ambient ter~gerature (20°C), followed by a vane pump at 67.5 Pa (0.5 mrHg) for a few minutes in order to eliminate all traces of solvent. This leads to compound (V) ta~der majority conditions (90%), with 10% of dimethacrylate obtained by reacting 2 moles of (III) with (N).
Access is obtained to the percentage of the isocyanate functions according to the traditional method of dosing NOO functions by dibutyl amine. This gives 12.8% in place of the theoretically calculated 13.4%.
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Carrying wt lubricatirn In order to obtain a lubricating level close to 0.5% on the carbon f fibre, a lubricating solution is prepared with 0.75 g of the mixture previ~sly obtained and containing unsaturated isocyanate(V) in 100 g of dichloromethane, to which is added a mixture of catalysts in the following proportions: 0.15 g (DBTDL) of dibutyl tin dilaurate + 0.22 g (DABCO) 1,4 ~iiazobicyclo-(2,2,2)-octane for 1 mole of isocyanate ( N).
Example 2 This example differs fran example 1 by the choice of the starting P~ucts respectively having the isocyanate function and the meth-acrylate function. The forniulas of the different ends used for producing this product are given in app~dix II.
Operating Conditions Dxvpwise addition takes place of 144 g (1 mole) of 2-hydrroxypropyl 15, methacrylate (VI) to a solution containing 168.2 g (1 mole) of hexa-methylene diisocyanate (VII) and 0.3 g of DBTDL, as well as 100 ppm of hyd~~quincne (polymerization inhibitor) in 300 g of ethyl acetate at a temperature of 60°C. Stirring and the tarQerature are maintained at 40°C for 5 hours. The solvent is evaporated with Rotavapor under 2.7 kPa (20 m~-ig) at anbient temperature (20°C). This gives compourxi (VIII) mixed with carr~pound (IX). The dosing of the isocyanate functions gives 12.97%, the theoretical percentage being 13.46%.
The lubricating product is obtained in the sane way as in example 1.
bcanple 3 ~ the ~~le the first gmup is once again an isocyanate group and the second group a maleate group. The products used for producing this lubricating product, as well as the reaction diagram are given in appendix III.
SP 5552.69 1~

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In the first stage 60 g (1 mole) of isoprvpa»ol (XI) are reacted with 98 g (1 rmle) of malefic anhydride (X) at 100°C for 2 hours and card (XII) is obtained quantitatively.
In the second stage 100 g (1 mole) of foxy hexane (XIII) are reacted with 0.1% by weight (based rn all the reagents) of chrcmium diisopmpyl salicylate (Cx~IPS) (unsaturated epoxide - acid reaction catalyst), added to 158 g (1 mole) of (XII). The reaction takes place at 100°C
for 3 hours, which gives cad (XIV) with an 86% yield.
The third stage involves the drapwise addition of 258 g (1 mole) of (XIV) to a solution containing 174 g (1 mole) of 2,4-toluylene diisocyanate (TDI) (XV) in 2 litres of anhydrous hexane under a dxy nitrogen stream at ambient ta~erature and accar~panied by stirring.
Bubbling is stopped after 7 hours, but stirring is allaaed to continue for a further 17 hags, haW ng ensured that no moisture can enter the reaction mixture.
The isocyanate-maleate ca~nd (XVI) obtained fornis a relatively viscous green oil, which is insoluble in hexane. It is thus extracted by the separation of two phases and is washed by hexane in order to eliminate the 2,4-TDI (XV), which has not reacted. The residual ~~e ~ filtered on a frit. Carpomd (XVI) is recovered by solubil-ization in dichlor<imethane. Finally, c~rrpomd (XVI) is obtained with a yiel3 of 93.5%. The perc~tage of NCO functions is 9.55% in place of the theoretically calculated 9.72%.
Lubrication is the same as in example 1.
bcanple 4 Preparation takes place of a lubricating solution containing 0.75 g of ~nnsaturated isocyanate (V) obtained in example 1 in 100 g of dichloranethane. Using this solution 1-IERCiULES IM6 carbon fibres, whose majority reaction sites are hydroxyl gxnups, were lubricated.
Lubrication took place 3n accordance with the diagram of fig. 3. The SP 5552.69 LC

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evaporation of the solvent and the reaction R1 between the isocyanate function and the d-1 sites were carried out at 50°C. This heat treat-ment lasted 15 seconds (passage speed 24 m/min and passage length 6 m).
The lubricated carbon fibres were the impregnated in a liquid resin mixture containing acxylate-epoxy resin and an acrylate-polyurethane resin.
This was follaaed by the winding of a N.O.L. ring (characterization modulus) making it possible to define the interlaninar shear between the fibres and the matrix. This N.O.L. ring was then irradiated with electrons at a dose of 50 kGy. During irradiation, the characteriz-ation ma3ulus underwent a irotation and a passage under the electron accelerator. The travel speed was 0.12 m/min for an electron accelerator of 6.2 MeV and T.5 kW.
The interlaminar shear characterization was performed in flexion according to three points. This gave an interlaminar shear stress of approximately 40 MPa.
Example 5 This example only differs from example 4 through the uae of a lubri-cating product (VIII) obtained in example 2. The car~ogition of the lubricating solution is the same as in exarrg>le 4.
The interlaninar shear stress measured for untreated X16 fibres lubricated by this lubricating product and anbedded in a matrix i~den-tical to that of example 4 is between 45 and 50 MPa.
Ccrr~arisa~ Example 1 A HERCULES IM6 carbon fibre with a lubricant G (which corresponds to a fibre in its carmercial form) was impregnated by a resin mixture constituted by an acrylate-epoxy resin and an acrylate-polyurethane resin identical to that of example 4. After producing a N.O.L. ring SP 5552.69 IBC

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and polymerizing the resin under the sane conditions as in example 4, the interlaninar shear stress of the N.O.L. ring was measured. The measured stress was between 20 and 30 MPa and is therefore belay that obtained in examples 4 and 5 according to the invention.
Comparative example 2 An unlubricated HERCULES DH6 carbon fibre was impregnated with a resin mixture of aciylate-epoxy resin and aczylate-polyurethane as in example 4. After producing a N,O.L. ring and polymerizing said ring in accordance with example 4, the interlaminar shear stress of the ring was measured and found to be close to 30 I~a.
It is clear fran examples 4 and 5 and comparative examples 1 and 2, that the use of a lubricating product according to the invention irnprnves the transverse stress characteristics of car~site materials.
Other lubricating products usable in the invention with CH group-rich 1,5 carbon fibres and a resin with acrylic texrninations, reference can be made to those given in appendix IV.
SP 5552.69 LC

2Q~5~"~6 APPRNT)TX T
Isocyanate-m~thacrylate Ruction NCO CH2=~-i0CH2CIH-OH
0 + 0 CH3 NCO
(IV) (II1) NCO

iH3 NH~O~HCH20~C=CH2 (V) SP 5552.69 LC

APPENDIX II
Isocyanate-m~thacrytate Reaction OCN-CHZ-(CH2)pCH2NC0 + CH2=C-~OCH2;H-OH

(V1I) (VI) CH2=C-COCH2CH-OGNH-CH2-(CHZ)4CH2NC0 (VIII) CHCH3-~OCH2~~O~NH(CH2)6NHb0~H~H20~C=CHZ

( I if ) SP SS52.b9 LC

~0154'~~

APPENDIX III
Isocyanate-maleate 1st Staae HC C~ ~ CHI
HC ~ /0 + CH3 HC C-OCH\
OPC C H
~CH-OH
H
0 CH3 ~-OH

(X) (XI) (XII) 2nd Stage ~CH3 (XII) ; CH2-CH-(CH2)3CH3 1-~ HC ~OCH \ CH3 CrDIPS HC~C=0 (XIII) d (XIV) ~H-(CH2)3-CH3 OH
3rd Stage s CH3 (XIV) t 0 hexane NCO

(XV) H
C=0 I

~H-(CH2)3CH3 tH2 He C=o (xVI) HC ~ =p QH~CH3 ~CH3 SP 5552.69 i_C

2054'76 APPENDTX TV
(XVI) CHZ= I-~0-CHZ-CH2-NCO
~H3 (XVI1) ~-CH=CH-GNH-CH2-CH2-Ut;NH- p -CH3, UN
NCU
(XVIII) CH3 ~CHO ~C/0 CH3 ~ H
jC - C/
H ~OCH2-CH-O~iNH~ CH3 I0 C4H9 0 ~/~NCO
(XIX) CHZ=CH-~CHZ-OIiNH-(CH2)b-NCU

SP 5552.69 LC

Claims (10)

1 1. Product for the reactive lubrication of carbon fibres having OH reaction sites for embedding in a resin hardenable by radiation according to a radical mechanism, constituted by a monomer having at least one first functional group able to thermally form covalent chemical bonds with the reaction sites and at least one second functional group differing from the first group and able to form covalent chemical bonds with said resin during its hardening under said radiation, the first group being chosen from among isocyanate, carboxylic acid anhydride, methylol and carboxylic acid chloride groups.

2. Product according to claim 1, characterized in that the second group is an ethylene unsaturation.

3. Product according to claim 1, characterized in that the first group is the isocyanate group.

4. Product according to claim 1, characterized in that the second group is chosen from among cinnamate, maleate, fumarate, styrene, acrylate, methacrylate and maleimide groups.

5. Product according to claim 1, characterized in that the second group is of the methacrylate or maleate type.

6. Composite material having carbon embedded in a resin hardened by radiation according to a radical mechanism, characterized in that it comprises a fibre lubricating product according to claim 1 ensuring the adhesion of the resin to the fibres.

7. Process for producing a composite material having carbon fibres embedded in a resin and comprising:
a) dissolving the carbon fibre lubricating product according to claim 1 in an organic solvent, b) depositing on the fibres the solution obtained in a), c) heating the fibres obtained in b) in order to evaporate the solvent and solely trigger the chemical reaction between the first group and the reaction sites of the fibres, d) impregnating the fibres obtained in c) with a resin hardenable by radiation according to a radical mechanism and e) subjecting the resin-impregnated fibres to the said radiation in order to copolymerize the lubricating product with the resin via the second group and hardening said resin.

8. Process according to claim 7, characterized in that into the solution obtained in a) is introduced a catalyst or a catalyst mixture in order to aid the chemical reaction of stage c).

9. Process according to claim 7, characterized in that the hardenable resin has an ethylene unsaturation.

10. Process according to claim 7, characterized in that the radiation is a X or beta radiation.