[Technical area]
The present patent application relates to the field of the manufacture of semiconductor products comprising a thermoplastic matrix and reinforcing fibers. It also relates to such semi-products and their use in the manufacture of composite parts.
[Prior Art]
Composite materials combining a thermoplastic resin for reinforcing fibers present because of their excellent mechanical properties with low weight of great interest in many fields, particularly in the aerospace industry, but also in the automotive industry and sports equipment.

These composites are usually manufactured by consolidation of semi-products made of reinforcing fibers coated with resin such as prepregs in the form of unidirectional sheets, strands or woven.

These semi-products can be obtained by impregnating the fibers by the resin. There are various methods of impregnation, in which the resin can be melted, dissolved in a solvent, or in the form of powder, or in fluidized bed or dispersed in an aqueous solution. Then the impregnated fibers are optionally freed from the solvent or the aqueous solution and then heated to melt the resin retained and form the semi-product.

The impregnation in an aqueous dispersion bath is interesting in economic and environmental terms. However, this method requires to obtain a uniform charge of the resin into fibers, to ensure a homogeneous distribution of the resin in the dispersion.

Thus, patent application WO 88/03468 proposes to stabilize the suspension by making it very viscous (at least 50 Pa-s) and adding further optionally a surfactant.

Using a similar approach, U.S. Patent 5,236,972 proposes to add a water soluble polymer, a wetting agent, and in addition a biocide, a plasticizer and an anti-foam agent to the dispersion.

U.S. Patent 5,888,580 proposes to use instead a low-viscosity dispersion and containing little dispersing agent, and controlling the charging of the fibers of resin through the resin concentration of the dispersion and the residence time. However, composite parts fabricated from such semi-products have a high porosity and non-optimum mechanical properties.

To remedy this problem, the application F 3034425 proposes to disperse the thermoplastic resin using a specific surfactant alkoxylated alcohol, namely alcohol ethoxylated stearyl 100 times, and to associate a stirring device to keep the homogeneous suspension. Thus, the authors claim to consolidate composite products without porosities. However, it is found that the addition of such a surfactant causes an increase in the viscosity of the resin, particularly in the high melting point polymer such as PAEK. A high resin viscosity can lead to subsequent forming defects. In fact, in the molten state, the polymeric resin too viscous is no longer able to flow properly. Therefore, it is difficult to

In particular, it is common to observe the occurrence of pleating surface and handling problems of the welds made during the assembly of composite parts in complex parts. These defects are exacerbated when the consolidation is carried out at a pressure below 5 bars.

In general, it is interesting to manufacture composite parts without resorting to high pressure, since it requires the use of expensive autoclaves.

The invention aims to overcome these problems and to provide a semi-preparation process may be converted into composite parts do not have the defects mentioned above.

It also aims to provide a semi-preparation process could be consolidated under suction outside autoclave.

More specifically, the invention aims to provide such a semi-preparation method in which the resin has a viscosity and a molecular weight that little change following the thermal cycles required for the manufacture of composite parts.

[Summary of the Invention]

The aims mentioned above have been achieved by a method according to the invention, wherein the reinforcing fibers are impregnated in an aqueous dispersion of resin powder comprising at least one thermally stable surfactant.

Indeed, the present invention relies on the finding that the quality of composite parts based PAEK resins depends in particular on the viscosity of the resin in the semi-product and its subsequent evolution. However, the high temperatures necessary for the manufacture and consolidation of semi-products based on PAEK (generally temperatures above 300 ° C) can cause the decomposition of compounds introduced during manufacture by reactive species,

which can result in chain extension reactions of PAEK can lead to connections. The increase in molecular weight which follows then increases the viscosity of the resin.

Now the systematic study of the different agents may be present in the semi-product based PAEK found firstly that the surfactant used in the dispersion was a primary factor of the increase in viscosity after a heat cycle and on the other hand that this effect was highly variable depending on the surfactant selected.

On this basis, it could be confirmed that the use of a thermally stable surfactant can limit the change in the viscosity of the resin and to obtain composite parts required quality.

Without being bound by this hypothesis, it is assumed that many surfactants break down in the PAEK resin due to the high temperature required for its transformation. The reactive species formed during the decomposition, in particular the radicals can then react with the polymer and cause chain extension reactions or hook, which increase the polymer molecular weight and thereby also its viscosity. However, when the resin has a high viscosity, it is no longer able to properly impregnate and coat the fibers, to ensure good adhesion of the semifinished products with each other or to marry the mold walls, which affects the quality of composite products obtained.

Also, according to a first aspect, the invention relates to a process for preparing a semi-product method comprising a base PAEK resin and reinforcing fibers, comprising the steps of:

at. Preparing a dispersion comprising a PAEK-based resin in powder form dispersed in an aqueous phase comprising at least one surfactant; b. Contacting the reinforcing fiber with said aqueous dispersion in order to obtain the impregnated fibers;

c. Drying the impregnated fiber dispersion; and

d. Heating the impregnated fibers to a temperature sufficient for melting the resin so as to form a semifinished product,

characterized in that the surfactant is a thermally stable surfactant.

Advantageously, the thermally stable surfactant comprises aromatic groups. According to another embodiment of the invention, the surfactant comprises a phosphoric group, phosphate or sulfonate. Preferably, these ionic groups.

Preferably, the reinforcing fibers are carbon fibers. Preferably, the reinforcing fibers employed in the process of the invention are not sized fibers.

When the reinforcing fibers are sized fibers, they are preferably sized with a thermally stable sizing.

Preferably, the PAEK resin is selected from the group consisting of polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether-ether ketone-ketone (PEKK), poly ether ketone ether ketone ketone (PEKEKK), poly-ether-ether-ketone-ether-ketone (PEEKEK), polyether-ether ether ketone (PEEEK) and poly-ether-diphenyl-ether-ketone (PEDEK), mixtures thereof and copolymers thereof with each other or with other members of the family of PAEK.

When it comes to PEKK resin, the PAEK resin is preferably a PEKK having a percentage by mass of terephthalic units relative to the sum of terephthalic and isophthalic units of between 35 and 100%, in particular between 50 and 90% and especially between 55 and 85%.

Advantageously, the pulverulent PAEK resin in the dispersion has a volume median diameter Dv50 of 1 to 300 μιτι, preferably from 5 to 100 and especially from 10 to 50 μιτι as measured according to Standard ISO 13 320, on a Insitec device Malvern.

According to a preferred embodiment, the semi-product is selected from a prepreg or a tape.

Furthermore, according to a second aspect, the invention relates to a semifinished product capable of being obtained by said process.

Preferably, the average molecular weight M w of the PAEK resin in the semi-product, as measured by size exclusion chromatographic analysis, does not increase more than 100%, especially no more than 50% and especially not more than 20% after heat treatment at 375 ° C for 20 minutes.

According to a third aspect, the invention relates to a dispersion useful in the preparation of a semifinished product comprising a PAEK-based resin and reinforcing fibers, comprising:

at. 1 and 50% by weight of basic PAEK resin having a Dv50 diameter between 1 and 300 μιτι;

b. 0001-5% by weight, calculated relative to the weight of the resin, of at least one thermally stable surfactant;

c. 0-1% by weight of other additives; and

d. the remaining water.

In a fourth aspect, finally, the invention relates to the use of a semi-product as described above for the manufacture of composites.

In the methods of manufacturing composite parts, semi-finished products are subjected to various thermal cycles under pressure or under vacuum in order to assemble them together to form the composite part and / or shaping.

[Brief description of Figures]

The invention will be better understood in light of the following description and the drawing, which shows:

Fig. Unique changes in the viscosity of a resin sample PEKK variable mass fiber in 20 minutes at 375 ° C under 1 Hz under nitrogen, according to Example 2.

[Description of Embodiments]

Definition of Terms

Is meant by the term "semi-product" designate products comprising a resin and reinforcing fibers used as intermediates in the manufacture of composite materials. These products may include prepregs in the form of unidirectional layers of rovings, woven, or mixtures fiber-matrices.

Semis can then be joined, for example by manual or automated layup or robotic removal ( "automated fiber placement") and shaped by consolidation, for the manufacture of composite parts. Thus manufactured composite parts can be processed further to obtain complex composite parts assemblies. Thus, it is possible to co-consolidating composite parts, generally process carried out in an autoclave by means of a new thermal cycle, or come weld parts to each other by local heating.

Is meant by the term "resin" a composition predominantly comprising one or more polymers added as appropriate conventional additives, including fillers and functional additives.

the term by means of "dispersion" refer to a heterogeneous composition comprising a liquid phase and a solid phase. In the dispersion employed in the method of the invention, the liquid phase is aqueous and contains a thermally stable surfactant and other additives, if necessary. The solid phase comprises or consists essentially of PAEK resin in powder form.

Is meant by the term "surfactant" refer to a compound having a hydrophilic portion and a lipophilic portion, and capable of dispersing the resin powder in the liquid phase and to keep it in suspension in the presence or absence of stirring. This compound may also assist in wetting the fibers with the dispersion.

Is meant by a "thermally stable surfactant" means a surfactant, which does not generate, when subjected to temperatures of 375 ° C for at least 20 min, reactive species capable of reacting significantly with the PAEK resin.

This property is evaluated by the following test: The PAEK resin in the form of powder (volume median diameter Dv50 = 20μιτι) is introduced into an aqueous solution containing 1% by weight relative to the resin amount of the surfactant to be evaluated (content resin dispersion: 1% by weight). The resulting mixture was stirred for 30 minutes using a magnetic stirrer. The water is then evaporated in an oven at 90 ° C for 48 h. This gives a dry residue of PAEK resin plus wetting agent. Then, subjecting a sample of the PAEK resin plus wetting agent to a heat treatment at a temperature of 375 ° C for a period of 20 minutes under nitrogen flushing.

It has proved difficult to measure the viscosity of these samples. Also, the viscosity of the PAEK resin added surfactant was evaluated by means of the molecular weight distribution as measured by size exclusion chromatographic analysis according to the following protocol.

About 30 mg of PAEK resin plus wetting agent to be evaluated are introduced into 1 ml of 4-chlorophenol and stirred for 24 h at 150 ° C. After cooling the solution to room temperature, 14 ml of hexafluoroisopropanol (HFIP) was added and the solution was filtered through a Acrodisc syringe type filter comprising a polytetrafluoroethylene (PTFE) membrane with a diameter of 25 mm and a porosity 0.2 μιτι.

The molecular weights of the resin are determined by size exclusion chromatography using a Waters Alliance 2695 model instrument using the following conditions:

Flow: 1.00 ml / min. Eluent: HFIP. Injection volume: 100.00 μΙ. PSS PFG column set (1000 + 100 Å) 2 * 30cm. Temperature 40 ° C. Detection mode: differential refractometer. Calibration: PMMA with a molecular weight range from 402g / mol to 1900000g / mol to update during each series of analysis.

The soluble content is measured by the ratio of the areas of the chromatograms of the sample analyzed on the one hand, and a reference soluble compound on the other hand prepared at the same concentration and injected in the same amount in the apparatus of chromatography.

When the average molecular weight M w of the PAEK resin increases by more than 20% relative to the resin before the heat treatment, the surfactant studied is classified as not thermally stable. Conversely, when the average molecular weight M w of the PAEK resin increases by 20% or less, the surfactant is classified as studied thermally stable.

"Thermally stable sizing" is meant by a sizing composition which does not generate, when subjected to temperatures of 375 ° C for at least 20 min, reactive species capable of reacting significantly with the PAEK resin.

This property is evaluated by the following test: is prepared an intimate mixture of 72 wt% PAEK resin (Dv50 = 20μιτι) and 28% by weight of sized fibers to assess in a mortar. Then, introducing a sample of the PAEK resin mixture of sized fibers into a plate-plate rheometer heated at 375 ° C and measuring the change in viscosity over 20 min. When the viscosity of the mixture increases to more than 20%, the size is classified as non-thermally stable. Conversely, when the viscosity of the mixture increases to 20% or less, the size of interest is classified as thermally stable.

The dispersion

The dispersion employed in the proposed method comprises according to the invention an aqueous phase comprising the PAEK resin in powder form and at least one thermally stable surfactant.

The PAEK resin essentially comprises at least one polymer polyaryletherketone (PAEK). The poly (aryl ether ketones) (PAEK) comprises the following units of formulas:

in which :

Ar and Ar are each a divalent aromatic radical;

Ar and Ar may be selected, preferably, from 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, naphthylene the 1,4-, 1,5-naphthylene and 2,6 -naphthylène, optionally substituted;

X is an electron withdrawing group; it may be chosen preferably from the carbonyl group and the sulfonyl group,

Y denotes a group selected from an oxygen atom, a sulfur atom, an alkylene, such as -CH2- and isopropylidene.

In these X and Y units, at least 50%, preferably at least 70% and more particularly at least 80% of the X groups are a carbonyl group, and at least 50%, preferably at least 70% and more particularly at least 80% of the Y groups represent an oxygen atom. According to a preferred embodiment, 100% of the groups X denote a carbonyl group and 100% of the Y groups represent an oxygen atom.

More preferably, the poly-arylene-ether ketone (PAEK) may be selected from:

- a polyether-ketone-ketone, also known as PEKK consisting of formula IA units of formula IB and their mixture:

I B

a poly-ether-ether-ketone, also known as PEEK, comprising units of formula II:

formulas II

The sequences can be totally para (Formula II). Similarly can be introduced partially or completely, sequences meta in these structures at the ethers and ketones according to the two examples of formulas III and IV below:

formula III

Or :

formula IV

Or ortho linkages according to the formula V:

Formule V

a poly-ether-ketone, also known as PEK, comprising units of the formula VI

Formule VI

Similarly, the sequence can be totally para but also can be introduced sequences meta partially or completely (formulas VII and VIII):

formulas VII

or

formula VIII

a poly-ether-ether-ketone-ketone, also known PEEKK comprising units of formulas IX:

formula IX

Similarly linkage can be introduced in these structures meta level ethers and ketones.

a poly-ether-ether-ether-ketone, also known PEEEK consisting of X units of formulas:

formula X

Similarly linkage can be introduced in these structures meta level ethers and ketones as well as sequences or BIPHENYLS biphenols of the formula XI (type D units in the next designations, the Formula XI corresponds to the label PEDEK)

Formule XI

Other arrangements of the carbonyl group and the oxygen atom are also possible.

Preferably, the PAEK used in the invention are selected from the group consisting of polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), poly ether ether ketone ketone (PEKK), poly ether ketone ether ketone ketone (PEKEKK), poly-ether-ether-ketone-ether-ketone (PEEKEK), polyether-ether-ether-ketone (PEEEK), and poly-ether-diphenyl-ether-ketone (PEDEK), mixtures thereof and copolymers thereof with each other or with other members of the family of PAEK. PEEK and PEKK and mixtures thereof are particularly preferred.

Advantageously, the stability of the PAEK in a molten state can be improved by adding one or more phosphate salts or phosphate.

Preferably, the PAEK resin comprises at least one polyether-ketone-ketone (PEKK), which represents more than 50%, preferably more than 60%, especially more than 70%, more preferred more than 80% and

especially more than 90% by mass of the resin terminal included. The remaining 10 to 50% by mass may consist of other polymers or may not belong to the family of PAEK.

More preferably, the PAEK resin consists essentially of PEKK.

Advantageously, the PEKK has a mass percent terephthalic units relative to the sum of the terephthalic units and isophthalic between 35 and 100%, in particular between 50 and 90% notably between 55 and 85% and preferably between 60 and 80%, and especially, the ratio is 65 to 75%.

The resin can also, as discussed above, also comprise other conventional additives such as fillers. Moreover, the resin can optionally contain minor amounts of functional additives. Preferably, the resin is nevertheless devoid of additives capable of decomposing under the effect of heat in order to limit the risk of change in viscosity. Even more preferably, the resin is free of functional additives.

The particle size of the PAEK resin powder may have an impact on the stability of the suspension. It can also influence the quality of impregnation resin of the reinforcing fibers. To ensure the optimum suspension of the homogeneity and good impregnation, it is preferred that the resin powder is finely divided. More specifically, it is preferred that the PAEK present powder a median diameter Dv50 is in a range from 1 to 300 μιτι, preferably from 5 to 100 and especially from 10 to 50 μιτι as measured according to ISO 13 320 .

Preferably, the powder content of the PAEK resin dispersion is advantageously between 0.1 and 50%, preferably between 1 and 40%, and more preferred between 10 and 30% by weight relative to the weight of the finished dispersion.

As mentioned above, the method according to the invention is characterized in that the dispersion also comprises at least one thermally stable surfactant. Indeed, studies have shown that the surfactant was the main factor in increasing the viscosity of the PAEK resin in a semi-observed following thermal cycle required for its consolidation.

The test described above assesses a surfactant in its ability to withstand the required temperatures without forming reactive species may react significantly with the PAEK resins. It is thus possible to determine simply and easily whether a surfactant is thermally stable within the meaning of the present invention.

As a thermally stable surfactant can be selected an ionic or nonionic. Preferably it is a nonionic surfactant, especially an anionic surfactant.

Preferably the thermally stable surfactant is a surfactant having at least one aromatic moiety, in particular one or more phenyl groups.

According to a particularly preferred embodiment, the thermally stable surfactant comprises a phosphoric group, phosphate or sulfonate. On the other hand, phosphates and sulfonates seem less likely to react with the PAEK resins than other surfactants when used in the method of impregnation by aqueous dispersion.

More specifically, there may be mentioned surfactants of the family of phosphoric acid esters. Preferably, it is monoesters or diesters of phosphoric acid. It may include phosphoric acid esters with alcohols, particularly alcohols containing 6 to 24 and especially 10 to 16 carbon atoms. Particularly preferred are phosphoric alkyl ether phosphates or sulfonates and alkyl aryl ether phosphates or sulfonates. Advantageously, it is of phosphates of alkoxylated alcohols, in particular methoxylated, ethoxylated or propoxylated. The number of molecules of alkoxyl by phosphate group can vary widely, and in particular be between 1 and 100, preferably between 2 and 50 and especially between 10 and 20.

As compounds of this family include in particular surfactants of the family of phosphoric ethers sold under the name Lanphos PE35 by Lankem company CECABASE T by the company CECA France and Klearfac AA270 by DeWolf society.

These surfactants can be used in free acid form, but it is preferably neutralized. Neutralization can be carried out beforehand or in situ in the dispersion by adding a suitable amount of sodium or potassium hydroxide.

The dispersion preferably contains not more than the minimum surfactant content required to stabilize the slurry adequately. This content depends on factors such as particle size of the PAEK resin, the amount of particles to be dispersed and the nature of the surfactant.

It may be interesting to add more thermally stable surfactants. In particular, one can choose a thermally stable surfactant to ensure good dispersion of the PAEK resin powder and other thermally stable surfactant to improve the affinity of the reinforcing fibers with the PAEK resin powder.

Nevertheless, most often, a surfactant content from 0.001 to 5% by weight, preferably 0.01 to 2, and most preferably from 0.1 to 1% and especially 0.2 to 0.8% by weight relative to the weight of resin makes it possible to ensure the stability of the suspension and good wetting of the fibers.

The aqueous phase of the dispersion may, if necessary, contain minor amounts of other conventional additives such as thickening agents, antifoaming agents, biocides. In order to limit the presence of additives in the semi-products and potential problems associated with the dispersion nevertheless has a content of preferably minimum other additives. Preferably, the amount of other additives does not exceed 1% by weight, and in particular 0,5% by weight of the finished dispersion.

To facilitate wetting of the fibers, the present dispersion preferably a viscosity less than 10 Pas, preferably less than 5, in particular between 0.0001 and 1, and preferably between 0.001 and 0.1 Pas at 20 ° C .

Preferably, the additives in the dispersion will be thermally stable, as determined by the test described previously. However, it is preferred that the aqueous phase of the dispersion comprises a minimum of additives, and in particular contains only the thermally stable surfactant.

The water used for preparing the dispersion is preferably demineralized water.

The method of preparation of the dispersion can be achieved in known manner. More specifically, the dispersion can be prepared by introducing in a volume suitable container and provided with a suitable stirring device the required amount of water and then adding the surfactant and the one or more other additives, if necessary. If necessary, the mixture is stirred until a homogeneous solution. In the aqueous solution is then introduced pulverulent PAEK resin and then stirred until a stable dispersion.

The reinforcing fibers

The reinforcing fibers can be in principle any fiber typically used in the manufacture of semi-products.

According to the invention, the reinforcing fibers may be selected from any fibers may be used as a reinforcement in the manufacture of composite parts.

Thus, it can be in particular glass fibers, quartz fibers, carbon fibers, graphite fibers, silica fibers, metal fibers such as steel fibers, aluminum fibers or boron fibers, ceramic fibers such as silicon carbide fibers or boron carbide, synthetic organic fibers such as aramid fibers or fibers of poly (p-phenylene benzobisoxazole), better known by the abbreviation PBO, or fibers of PAEK, or mixtures of such fibers.

Preferably, it is carbon fiber or glass fiber, particularly carbon fibers.

According to a preferred embodiment, the fibers do not induce in combination with other compounds of significant change in the viscosity of PAEK in the semi-product and in the composite.

The fibers are preferably non-sized. If they are sized, they are preferably sized through a thermally stable sizing composition as defined above.

The reinforcing fibers used in the manufacture of semi-products by impregnation by means of an aqueous dispersion are generally continuous.

Preferably they are in the form of unidirectional fibers, such as son gathering thousands of elementary filaments (typically 3000-48000) measuring, for example, 6-10 μιτι diameter for carbon fibers. This type of fiber is known under the wick name (in English "rovings").

The fibers may however also be arranged differently, for example in the form of mat, textile or strands obtained by weaving.

The semiconductor manufacturing process

The manufacturing method according to the invention can be carried out conventionally, on the usual equipment, by applying the dispersion as described above. As indicated above, the presence in the dispersion of a thermally stable surfactant allows to limit the formation of reactive species capable of increasing the molecular weight of the resin and therefore its viscosity and in this way reduce the appearance defects in composite parts.

More specifically, the semi-products are obtained by introduction and circulation of the reinforcing fibers in a bath of such an aqueous dispersion described above. The PAEK resin impregnated fibers are then removed from the bath and dewatered, for example by drying in an oven at infrared. The dried impregnated fibers are then heated until melting of the resin, to allow the coating of the fibers by the PAEK resin. The obtained coated fibers then are optionally formatted, for example by calendering, so as to shape and size the semi-product.

Preferably, the semi-product according to the invention comprise from 1 to 99% by weight, preferably 30 to 90%, especially 50 to 80% by weight and in particular 60 to 70% by weight of reinforcing fibers.

The semi-products manufactured by the process of the invention are characterized in particular by a resin whose viscosity has changed little despite the high temperatures required for their manufacture in order to melt the resin.

The semi-products obtained according to the process of the invention can be used especially for the manufacture of composite parts.

Composite parts are obtained for example by first making a preform, in particular by placement or draping semifinished products prepregs into a mold. The composite part is then obtained by consolidation step in which the preform is heated and compressed, for example in an autoclave or in a press, so as to assemble by melting the semi-products.

The composite products manufactured according to the method of the invention are characterized in particular by a resin whose viscosity has changed little despite the high temperatures required for their manufacture.

During these steps, a too high viscosity of the matrix is ​​crucial to ensure that the semi-marry well forms the mold. The viscosity of the matrix also ensures a good flow during consolidation and thus avoid surface defects such as wrinkling.

The invention is explained in more detail in the following examples.

[Examples]

Example 1-3: Variation of the viscosity according to the semi-product of the manufacturing process

The impact of thermal cycling on the evolution of the viscosity has been studied for a PEKK resin (Kepstan 7003, sold by Arkema France) and for semi-products made from this resin and carbon fibers by various methods.

Prepregs were made laboratory scale with 70% by weight of Kepstan 7003 resin and 30% by weight of carbon fibers on the one hand by a method melt-and secondly by way of dispersion, depending the following respective protocols:

1) Method of impregnating spunlaid:

Is positioned about 8 g strands of carbon fibers (12K Fiber epoxy-compatible sizing E13 marketed under the name of HTA40 by Toho Tenax-) on a polyimide sheet (thickness 50μιτι of Upilex film sold by the company UBE ) with an aluminum adhesive resistant temperature.

The strands of carbon fibers are then sprinkled with 20 g of PEKK powder (marketed under the name Kepstan 7003 by Arkema France, Dv50 = 300μιτι) homogeneously using a vibrating screen. then covers the PEKK powder surface by a second polyimide sheet.

The assembly is then placed between two sheets of steel and is passed under a CA VE press at 375 ° C for 1 minute at 5 bars. The assembly is then removed from the press and allowed to cool to room temperature.

After takeoff polyimide sheets and cutting aluminum adhesives, there is obtained a prepreg prepared by melt channel. the prepreg obtained is divided into two parts.

2) A method of impregnation by aqueous dispersion:

An aqueous surfactant solution by introducing into a flask 1000g of water and 0.1g of surfactant Triton ™ X100 (t-octylphenoxypolyethoxyethanol) sold by Dow. The aqueous solution is homogenized for 10 minutes using a magnetic stirrer.

then gradually introduced 4 g of carbon fibers sized (E13 HTA40 sold by Toho Tenax-) cut to a length of 1 cm into the vial containing the aqueous solution with vigorous stirring with a homogenizer Ultra-Turrax type. The dispersion was finally homogenized for 10 minutes. At the end of this step, the carbon fibers were ground homogeneously and are suspended in the aqueous solution.

Then 10 g was added of PEKK powder (marketed under the name Kepstan 7003 by Arkema France, Dv50 = 20μιτι) and the resulting mixture was stirred for 30 minutes using a magnetic stirrer.

The water is then evaporated in an oven at 90 ° C for 48 h.

Thus, a homogeneous mixture of powder PEKK plus wetting agent and carbon fibers. then sends a prepreg by pressing at 375 ° C under 5 bars for 1 minute as described above.

Both prepregs made respectively spunlaid and by means of an aqueous dispersion are then subjected to a thermal cycle required for reproducing the consolidation of semifinished products. The thermal cycle consists of a passage in an oven at 375 ° C for 20 minutes under nitrogen flushing.

Then measured the number average molecular weight M w of the PEKK resin by steric exclusion chromatography, according to the protocol below to:

the untransformed PEKK resin (Example 1)

the sample obtained by a melt route (Example 2) and

- the sample contacted with a surfactant as in a impregnation method by means of an aqueous dispersion (Example 3).

For Examples 2 and 3, the measurement is carried out for the sample before and after the heat cycle.

Approximately 30 mg of the sample are introduced into 1 ml of 4-chlorophenol and stirred for 24 h at 150 ° C. After cooling the solution to room temperature, 14 ml of hexafluoroisopropanol (HFIP) was added and the solution was filtered through a Acrodisc syringe type filter comprising a polytetrafluoroethylene (PTFE) membrane with a diameter of 25 mm and a porosity 0.2 μιτι.

The molecular weights of the resin in the sample are determined by size exclusion chromatography using a Waters Alliance 2695 model instrument using the following conditions:

Flow: 1.00 ml / min. Eluent: HFIP. Injection volume: 100.00 μΙ. PSS PFG column set (1000 + 100 Å) 2 * 30cm. Temperature 40 ° C. Detection mode: differential refractometer. Calibration: PMMA with a molecular weight range from 402g / mol to 1900000g / mol to update during each series of analysis.

The soluble content is measured by the ratio of the areas of the chromatograms of the sample analyzed on the one hand, and a soluble compound reference prepared at the same concentration and injected in the same amount in the chromatograph else share. The insolubles content then consists of the rate of carbon fiber and the rate of insoluble polymer. then take care of subtracting the amount of carbon fibers to obtain only the rate of insoluble polymer.

The results are summarized in Table 1 below.

The results in Table 1 demonstrate that the evolution of the average molecular weight M w of the resin in the sample containing a surfactant as necessary in the dispersion channel is more than twice that in a semi-manufactured product spunlaid.

In addition, it is noted in Example 3 carried out by means of dispersion, a significant increase in the insoluble fraction, indicating that part of the polymer is modified to the point that it can no longer be dissolved in the experimental conditions.

Table 1: Changes in the average molecular weight M w of the resin PEKK

Example 4 12: Evolution of the viscosity depending on the nature of the carbon fibers

The impact of thermal cycle on the evolution of the viscosity was investigated for samples containing carbon fibers from different manufacturers and sized or not. The fibers used herein are as follows:

Fiber HexTow AS4 marketed by Hexcel (not ensimée).

Fiber HexTow AS4D marketed by Hexcel (not ensimée).

- Fiber Tenax HTS45 P12 marketed by Toho-Tenax (with thermoplastic sizing compliant).

Tenax Fiber HTA40 E13 sold by Toho Tenax-(epoxy-compatible sizing).

PEKK resin mixtures and these carbon fibers were manufactured according to the following protocol:

An amount of 2 g of powder of PEKK resin (Kepstan 7002, sold by Arkema France, Dv50 = 20μιτι) is introduced in a mortar. An amount 14, 28 and 43% by weight, relative to the total weight of the sample of staple fibers to a length of 0.5 cm.

Mechanical mixing is carried out in the mortar in the presence of few drops of water to assist in the wettability and good dispersion of the fibers in the resin. The mixtures thus prepared were then dried for 12 hours under vacuum at 120 ° C. is then measured for each sample viscosity in a plate-plate rheometer under nitrogen (1 Hz) to 375 ° C as a function of time for 20 minutes. The evolution of viscosity (in%) under the effect of thermal cycling reproducing that required for the consolidation of semi-products can be evaluated by comparing the viscosity value measured at the initial time and after 20 minutes of test.

The results for the different mixtures are made in Table 2 below and to the single figure.

Table 2: Composition of Examples and change in viscosity

The results in Table 2 and the single figure show that the presence of carbon fibers has a significant effect on the evolution of the viscosity of the PAEK resin. Moreover, we note that this effect is highly variable depending on the nature of the fibers implemented. In particular, it is found that non-sized fibers have a lesser effect in comparison with the sized fibers. Among sized fibers, it also notes that some sizings can have a very detrimental effect on the viscosity of the resin PAEK.

Also, it can be inferred from this study the link between the increase in viscosity and the presence of alien species, after heat treatment. otherwise it is concluded that the advantage of using fibers preferably not sized.

Example 13-21: Evaluation of thermal stability of surfactants

The impact of thermal cycling on the evolution of the average molecular weight M w was investigated for a PEKK resin (Kepstan 7002, sold by Arkema France) for different surfactants.

The samples were manufactured using the following protocol:

An aqueous surfactant solution by introduction into a vial of water and 1000g of 0.1g of a surfactant. The aqueous solution is homogenized for 10 minutes using a magnetic stirrer. Then 10 g was added of PEKK powder (marketed under the name Kepstan 7002 by Arkema France, Dv50 = 20μιτι) and the resulting mixture was stirred for 30 minutes using a magnetic stirrer. The water is then evaporated in an oven at 90 ° C for 48 h. Thus, a homogeneous mixture of powder PEKK added surfactant.

The various examples are prepared with the surfactants indicated below.

The surfactant Cremophor ® A25 (C16-C18 alcohol ethoxylate) marketed by BASF.

- The surfactant Brij ® S 100 (ethoxylated stearyl alcohol) sold by the company Sigma-Aldrich.

The surfactant Lanphos PE35 (isotridécyléthoxyphosphate) sold by the company Lankem, used here in the form neutralized with sodium hydroxide designated "Lamphos PE35Na". The surfactant Agrosurf DIS145 (condensate of sodium naphthalenesulfonate and formaldehyde) sold by the company Lankem.

The surfactant Triton ™ X100 (t-octylphenoxypolyethoxyethanol) sold by Dow.

The surfactant Triton ™ G -7ME (dioctylsulfosuccinate dissolved in aromatic hydrocarbon) sold by Dow.

A portion of the prepared samples is used to measure the average molecular weight M w of the PEKK resin before and after heat cycle as described in Example 3. The results are summarized in Table 3 below.

Table 3: Weight average molecular weight M w of PEKK resin containing different surfactants

Ex Material Before Aftern ring; cycle thermal Evolution therr 1IC read [%]

Mw In; ;olubles Mw Insol jbles

[g/mol] (% ) [g/m ol] (%)

13 65000 68000 Resin PEKK only 5%

(reference)

14 PEKK resin with 1% 65000 87000 <5% 22%

tensioactif Crem ophöre ®

A25

15 PEKK resin with 1% 65000 84000 <5% 25%

surfactant Brij ® S 10 0

16 PEKK resin with 1% 65000 72000 <5% 10%

surfactant Lanphos F> E35Na

17 PEKK resin with 1% 65000 69000 <5% 5%

surfactant Agrosurf DIS145

18 PEKK resin with 1% 65000> 100000> 5% 70%

surfactant Triton ™> 100

19 PEKK resin with 1% 65000 91000 <5% 40%

surfactant Triton ™ IR-C 7ME

The results in Table 3 above show a marked effect of the choice of surfactant on the evolution of the viscosity of the resin PAEK.

In particular, it is noted that surfactants Lanphos PE35Na and Agrosurf DIS145 are thermally stable with PEKK in the test conditions, since the average molecular weight M w of the resin increases less than 20% after a heat cycle of 20 min to 375 ° C.

In contrast, surfactants Cremophor ® A25, Brij ® S 100, Triton ™ GR-7ME and Triton ™ X100 tested do not satisfy this test, since the average molecular weight M w of the resin increases by 30% or even up to 70%.

Thus, the evolution of the average molecular weight M w of Example 18 carried out with the surfactant Triton ™ X100 is very significantly greater than that measured on the samples of Examples 16 and 17 made respectively using surfactants PE35Na and DIS145.

The elements reported above show that the nature of the surfactant is an important factor to control the evolution of the viscosity and the average molecular weight M w of PAEK resin subjected to a thermal cycle representative of the time required for consolidation of a semi-product in composite parts.

Example 20-22: Variation of the viscosity depending on the surfactant

The impact of thermal cycling on the evolution of the average molecular weight M w was investigated for a PEKK resin (Kepstan 7002, sold by Arkema France) with different surfactants, in the presence of carbon fibers not sized AS4D marketed by Hexcel.

The samples were manufactured according to the protocol of Example 3 above, with the surfactants indicated below.

The surfactant Cremophor ® A25 marketed by BASF.

The surfactant Lanphos PE35Na marketed by Lankem society.

Subjecting a portion of the prepared samples to thermal cycling and then measures the average molecular weight M w of the PEKK resin samples before and after thermal cycle as described in Example 3.

The results are summarized in Table 4 below.

Table 4: Weight average molecular weight M w of PEKK resin containing different surfactants

Ex Material Before cycle after cycle Evolution thermiqi I thermiqui []

Mw Insolubles Mw Insolubles

[G / mol] (%) [g / mol] (%)

20 PEKK resin only 65000 68000 5%

(reference)

21 PEKK resin with 30% 65000 87000 <5% 30%

AS4D fibers and 1%

surfactant Cremophor ®

A25

22 PEKK resin with 30% 65000 75000 <5% 15%

AS4D fibers and 1%

surfactant PE35Na

The results in Table 4 show a marked effect of the choice of surfactant on the evolution of the viscosity of the resin PAEK.

Indeed, the surfactant is more stable with PE35Na PEKK in the test conditions that the surfactant Cremophor ® A25. The evolution of weight average molecular weight M w of Example 21 made with the surfactant Cremophor ® A25 is very significantly greater than that measured on the sample of Example 22 made using the surfactant PE35Na.

In addition, there is a significant fraction insoluble in the sample, reflecting the presence of polymer can not be dissolved by the experimental protocol.

It is found for all studies reported above that the nature of the surfactant is an essential factor for the change in viscosity and the average molecular weight Mw of a PAEK resin subjected to a thermal cycle representative of the required for the consolidation of a semi-product in composite parts.

This effect may nevertheless be significantly reduced by appropriate choice of surfactant. In particular, the use of a thermally stable surfactant to PAEK polymers with melting temperatures allows to limit the formation of reactive species.

Furthermore, the choice of suitable reinforcing fibers, sized or not, yet reduces the increase in viscosity.

The use of a thermally stable surfactant in the manufacture of semi-products by the method of the invention thus allows, maintaining the viscosity of the PAEK resin, to ensure a good quality composite parts obtained from those -this.

[List of documents mentioned]

WO 88/03468

US 5,236,972

US 5,888,580

F 3 034 425

Claims

1. A process for preparing a semi-finished product comprising a base PAEK resin and reinforcing fibers, comprising the steps of:

at. Preparing a dispersion comprising a PAEK-based resin in powder form dispersed in an aqueous phase comprising at least one surfactant; b. Contacting the reinforcing fiber with said aqueous dispersion;

c. Drying the impregnated fiber dispersion; and

d. Heating the impregnated fibers to a temperature sufficient for melting the resin so as to form a semifinished product,

characterized in that the surfactant is a thermally stable surfactant.

2. Preparation process according to claim 1, wherein the surfactant the surfactant comprises aromatic groups.

3. Preparation process according to one of claims 1 to 2, wherein the surfactant comprises a phosphoric group, phosphate or sulfonate.

4. Preparation process according to one of claims 1 to 3, wherein the reinforcing fibers are carbon fibers.

5. Preparation process according to one of claims 1 to 4, wherein the reinforcing fibers are not sized.

6. Preparation process according to one of claims 1 to 5, wherein the reinforcing fibers are sized fibers with a thermally stable sizing.

7. Preparation process according to one of Claims 1 to 6, wherein the PAEK resin is selected from the group consisting of polyether ketone (PEK), polyether ether ketone (PEEK), polyether-ether ketone-ketone (PEEKK), poly ether ether ketone ketone (PEKK), poly ether ketone ether ketone ketone (PEKEKK), poly-ether-ether-ketone-ether-ketone (PEEKEK) , poly-ether-ether-ether-ketone (PEEEK), and poly-ether-diphenyl-ether-ketone (PEDEK), mixtures thereof and copolymers thereof with each other or with other members of the family of PAEK.

Preparation process according to one of Claims 1 to 7, wherein the PAEK resin is a PEKK having a percentage by mass of terephthalic units relative to the sum of terephthalic and isophthalic units of between 35 and 100%, in particular between 50 and 90% and especially between 55 and 85%.

Preparation process according to one of claims 1 to 8, wherein the pulverulent PAEK resin in this dispersion a volume median diameter Dv50 as measured according to ISO 13 320 1 to 300 μιτι, preferably from 5 to 100 and especially 10 to 50 μιτι.

Preparation process according to one of Claims 1 to 9, wherein the semi-product is selected from a prepreg or a tape.

11. A dispersion useful in the preparation of a semifinished product comprising a resin based on PAEK and reinforcing fibers, comprising:

at. 1 and 50% by weight of basic PAEK resin having a Dv50 diameter as measured according to ISO 13320 of between 1 and 300 μιτι;

b. 0001-5% by weight, calculated relative to the weight of the resin, of at least one thermally stable surfactant;

c. 0-1% by weight of other additives; and

d. the remaining water.

12. Semi-finished product comprising a resin based on a PAEK and reinforcing fibers, obtainable by the process as defined in the preceding claims.

13. Semi-finished product according to claim 12, wherein the weight average molecular weight Mw of the PAEK resin, as measured by size exclusion chromatographic analysis, does not increase more than 100% after heat treatment at 375 ° C for 20 minutes.

14. Use of a semifinished product according to one of claims 12 to 14 for the manufacture of composite materials.