FR2463159A1 - Rheologically stable semi-finished prods. contg. thermosetting resins - fibres and fillers, and having good mechanical and electrical properties - Google Patents

Abstract

Semi-finished prods. in plate or blank form and having stable rheological prop. on storage comprise 10-80 (15-40) (wt)% mineral or synthetic fibres in the form of mats, fabrics or strands, 5-70 (10-40)% thermosetting resin and 5-60% of a filler. The prods. are obtd. (semi)continuously introducing a powdery formulation of the resin and the filler into the fibrous structure, heating at a temp. equal to or above the softening pt. of the resin but so that the crosslinking rate of the resin remains low, compacting the resin-loaded fibrous structure under pressure and hardening the prod. by cooling and storing in the form of strips, plates or blanks. Specifically the resin is a phenolic novolak, an aminoplast, a polyester, a polystyrylpyridone, a polybismaleimide or an epoxy resin. The filler is an active and/or passive (in)organic filler in the form of powder, beads or grains such as sand, slate, trihydrated alumina, silica and boric anhydride. The fibres are pref. glass fibres and/or carbon fibres. The prods. have good mechanical and electrical properties that cen be adjusted to suit the purpose required and also have good fire resistance. They can be used as structural materials in e.g. aircraft interior and other vehicles, public buildings, cable channels and the like.

Description

 The invention relates to composite semi-finished products that can be used as dry prepregs, comprising a fibrous structure coated with a formulation based on at least one powdery thermosetting resin and a filler and the use of said products for the manufacture of finished products. in particular plates or shaped parts whose mechanical properties, electrical and fire resistance can be easily adjusted.

 Various types of prepregs obtained by impregnation of a fibrous mass by means of a thermosetting resin either in the liquid state or in the powdery state are already known. Most of these prepregs give shaped finished products such as strips, plates, shaped pieces, etc., having particular physical properties.

Thus some have good mechanical properties such as those obtained from liquid resins, but they do not have both good mechanical properties, good electrical properties and fire resistance in particular. Others, on the other hand, such as those obtained from pulverulent resins may have satisfactory electrical properties and / or fire resistance but their mechanical properties are sometimes insufficient or conversely. In any case, to the knowledge of the applicant, the prepregs or semi-finished products manufactured so far do not have good rheological properties which results in limited lifetimes and storage difficulties.

 Furthermore, if there are finished products combining good mechanical, electrical and fire resistance properties, these properties are not adjustable according to the needs and these products are obtained only by using demanding application processes. severe operating conditions (temperatures and times) and expensive raw materials.

 However, the present invention provides finished products having both good mechanical, electrical and fire resistance properties that can be easily adjusted depending on the desired application while using simple processes and inexpensive raw materials.

 The prepregs or precoated according to the present invention are obtained using simple installations; dry blending and incorporation of the powdered ingredients, including fillers at high concentrations, into the fiber structure do not pose any particular problems; the absence of solvents or nonreactive liquid component in the compositions eliminates the risk of porosity formation by volatilization thereof; and finally said pre-coated particles can be stored practically indefinitely at room temperature while maintaining a stable rheological behavior over time, the crosslinking agent being solid and therefore not able to diffuse. They can then be formed by conventional methods and thermally treated for their final hardening.

 The present invention therefore relates to a product consisting of a continuous fibrous structure with a thermosetting resin composition, using the fact that the resin, after introduction in powder form into the fibrous structure, passes, when heated, a thermoplastic stage Thus, after spreading the powder formulation in the fibrous structure with the aid of a conventional dusting device, it is possible to preheat and compact the whole under a suitable pressure and at a temperature slightly greater than or equal to the softening temperature. the resin, but such that the rate of crosslinkingreste low. Cooling then gives plates or blanks not adhering to each other and sufficient mechanical properties to be stored and handled easily.

By heating at a temperature greater than or equal to that of compaction, the plate or the blank becomes sufficiently plastic to be able to be finalized by any conventional method, before crosslinking and irreversible thermosetting.

 The present invention thus provides, whether continuous or not, semi-finished products in the form of sheets, sheets, flat or shaped strips, blanks, and resulting finished products obtained by conventional processing methods, such as molding by forming, stamping, calendering ..., this enumeration is not exhaustive.

 The installation may include, for descriptive and nonlimiting reasons, the following devices - a device for mixing the ingredients if necessary; a device for feeding fibrous product: reel of mats ...

- a conventional dusting device distributing the formula
at a fixed and adjustable rate, in relation to the material
fibrous - a preheating device if necessary - a compacting device that can be a calandria train
ensuring adequate heating and pressure, in the case of a
fibrous material in a continuous strip, or a heating press in
the case of a discontinuous material - a cutting device if necessary (
tinue and edges).

The set of devices above or any other
similar equipment, allows to obtain the semi product
finished according to the invention.

The use of this semi-finished product for its implementation
final form and its cross-linking, can be done using
any suitable shaping device: press heater
fante ..., possibly followed by post-cooking.

According to a variant, it suffices, after the devices
supply of fibrous product, dusting of resin,
possibly heating and shaping: press
heating, calender trains ..., to use the product
uncooled semi-finished product by possibly associating it with a
other material, for the production of finished products com
plexes and thus to perform the coating, the forming and the
crosslinking of the complex structure into a series of
consecutive rations possibly followed by a post
cooking.

All things being equal, by the way, the pro
properties, in particular mechanical, electrical and holding
in fire, finished products obtained are indirectly after intermediate storage of semi-finished products either directly, without intermediate storage, are identical.

 The fibrous materials used in the products of the invention comprise mineral or synthetic fibers in the form of mats, fabrics or wicks, advantageously glass and / or carbon fibers. The proportion of these materials is between 10 and 80% by weight, preferably between 15 and 40%.

 The resins used in the production of the products of the invention are all thermosetting powder resins having, in the presence of curing agents if necessary, a "thermoplastic range" in a range of temperature-and of sufficiently long duration to allow the manufacture of the products according to the invention. Their proportion is between 5 and 70% by weight, preferably between 10 and 40% by weight.

 Novolac-type phenol resins are among those which lend themselves best to the production of the products of the invention. Other resins such as aminoplasts, polyesters, polystyrylpyridines (PSPs), polybismaleimides, epoxides, etc. can be advantageously used depending on the desired properties.

 As for the feeds also entering into the products of the invention, these are chosen from active and / or passive, mineral and / or organic fillers in the form of powders or beads preferably of a particle size close to that of resin. Examples include sand, slate, alumina trihydrate, silica, boric anhydride, this list is not exhaustive. The proportion of these fillers is between 5 and 60% by weight.

A judicious choice of the nature and the proportion of each component of the products according to the invention (resin, filler, fibers) makes it possible to obtain these products essentially characterized by a particular combination of their physical properties and in particular
- a fire resistance of 40 to 100 (expressed in index
limit oxygen (IOL) according to ASTM D
286370
- a breaking stress of 100 to 500 and more
(expressed in NPa according to NF.T. 51001),
- a module of 15,000 to 40,000 and over (expressed in
MPa following NF. T. 51001) properties associated with good electrical properties, density to meet the desired applications, a low rate of toxic gases emitted by combustion and low cost.

 Pre-asphalt used alone or in assemblies of several identical or different layers can be assembled during the final shaping to sheets or layers such as metal, veneer, fabric, decorative paper and / or hollow structures (nests). bees, deployed materials and the like) of identical or different materials for giving them structural and / or surface determinin properties.

 The ability to adjust the properties of the finished products of the invention and to provide various composite structures provides the industry with materials particularly useful as structural and / or cladding materials in confined atmosphere in applications such as inside aircraft and other vehicles, public buildings, cable trays ... these examples are not exhaustive.

 The examples given below are in two parts Examples 1 to 3 relate to the manufacture of semi-finished or precoated products and Examples A to K those of objects or finished products obtained from precoated products. These various examples explain the present invention and are in no way limiting.

I. Manufacture of pre-coated.

 The implementation described below is usable for the production of any precoated according to the invention continuously or discontinuously. Only the numerical data (temperature, pressures, durations ...) vary according to the formulations and are provided with each example.

They are not optimized.

 After incorporating any additives, of a compatible particle size (curing agents, fillers, dyes), into the base resin, using any conventional powder mixing device, a layer of the mixture is placed on the mold. resulting, a continuous fiber reinforcement layer, a new layer of mixture and so on until the desired structure is obtained. It is then heated to a temperature at which the resin softens, either in an oven, or under docking pressure between the trays of a mold. When the resin is sufficiently fluid, pressure is exerted so that the formulation is distributed correctly between the fibers and coats them as completely as possible, a slight creep occurring during this operation. It is then cooled under docking pressure until resolidification and demolding.

 The precoated products obtained have a lifespan equal to that of the base resin and can therefore be stored at room temperature for long periods of time without an anti-adhesive interlayer.

The mechanical properties allow storage and handling necessary for the realization of the final phase of implementation.

The percentages indicated are by weight
Example 1. (Witness) Components
phenol resin novolac type PB 10 of
RHONE-POULENC: 80%
- Unifilo glass mat (2% binder) - 375 g / m2 20%
de-SAINT-GOBAIN 3 ply 20 x 20 cm Conditions
preheating at 1200C for 7 minutes
- Compaction at 1100C under 10 bars for 30 sec.

- cooling up to 70 ° C under pressure
docking.

A light brown plate approximately 4 mm thick is obtained.

Example 2

components
phenol resin novolac type PB 10 40%
- alumina trihydrate DT 080 CYBA 40%
- Unifilo glass mat, 375 g / m2 3-ply
20 x 20 cl 20% Conditions
- preheating 1200C for 7 minutes
- Compaction at 1200C under 15 bars for 1 min
- cooling at 700C under accosive pressure
floor.

A light brown plate approximately 4 mm thick is obtained.

Example 3

components
phenolic resin type Novolak PB 10 40%
- alumina trihydrate CYBA DT 080 36%
- boric anhydride 4%
- matte Unifilo 375 g / m2 3 ply 20 x 20 cm 20%
Conditions: the same as in example 2.

A light brown plate approximately 4 mm thick is obtained
Example 4

components
phenolic resin type Novolac PB 10 40 96
- slate powder (~ 50p) 40%
- matte Unifilo 375 g / m2 3 ply 20 x 20 cm 20%
Conditions: Same as in example 2.

A black plate approximately 4 mm thick is obtained.

 The heating times indicated in the examples above and corresponding to passages in a ventilated oven or between the trays of the molds can be significantly reduced by using a high frequency heating.

II. Examples of production of finished products from
precoated.

 The use of pre-coated to obtain finished products can be carried out in various ways, however, the basic operations described below are practically in all cases.

 The precoated material is preheated, alone or in combination with finishing layers and / or core material, in an oven or at mold pressure, at a temperature greater than or equal to the precoated compacting temperature.

 It is formed at a higher temperature by applying the maximum molding pressure only when the crosslinking is sufficiently advanced to avoid significant creep.

 The crosslinking is then perfected by maintaining the pressure and possibly raising the temperature and then demolding, either hot or after partial cooling to eliminate deformations, in particular in the case of flat parts.

 If the conservation of the mechanical properties in temperature is necessary post-cooking in an oven without pressure is carried out because it allows by ensuring a further crosslinking to increase the thermostability.

 The numerical parameters as well as the specific conditions are given in the examples below. On the other hand, the numerical values of the properties of the various products are summarized below in the table below.

Example A. (Witness)
Component: a plate of 20 x 20 cm of pre-coated
as obtained in Example 1.

terms
preheating at 1250C for 5 minutes in an oven;
- heating under pressure at 1500 / 1600C
running at 15 bars at 150 / 1600C for 2 minutes
nutes;
- post-cooking in an oven for 3 hours at 1700C.

A brown plate approximately 3 mm thick is obtained which is easy to remove from the mold and has a good surface appearance.

Example B.

Component: a plate of 20 x 20 cm of pre-coated such
obtained in Example 1.

terms
- Preheating at 1250C for 5 minutes in an oven
- heating under pressure at 1500 / 1600C
molding at 20 bar at 150 / 1600C for 2 minutes
- post-cooking for 3 hours at 1700C.

A plate of appearance similar to that of Example A is obtained.

Example C.: Shaped Object
Component: a plate of 15 x 15 cm of pre-coated such
obtained in Example 2.

terms
- Preheating in an oven at 1250C for 5 minutes
- heating of the mold (cone 80 mm in diameter and
50 mm high) and punch at 1500C
- molding at 1500C by progressively exerting a
strength of 3 tons on the punch and in the mainte
3 minutes at 1500C
- post-cooking for 3 hours at 1700C.

 -The cone obtained after easy demolding and deburring has a smooth surface without gaps; its thickness is regular.

Example D: Shaped Object
Component: a plate of 33 x 33 cm of pre-coated such
obtained in Example 2.

terms
- Preheating at 1250C for 5 minutes in an oven
- heating of the mold (form: corrugated iron sheet
bright gules of 25 x 35 cm useful) and against
1500C mold;
- forming at 1500C under docking pressure
- molding and crosslinking at 1500C for 3 minutes
by exerting a force of 15 tons.

Example E.

Components: a plate of 10 x 10 cm of pre-coated
as obtained in Example 2.

- a piece of copper foil of 35 ju
10 x 10 cm with one side treated for amé
improve adhesion to the resin.

terms
preheating the precoated at 1250C for 5 minutes
utes
- introduction of pre-coated and foil
copper between the mold trays heated to
1800C and application of docking pressure
- molding under 35 bar at 1800C for 2 minutes
- cold demoulding.

 After deburring, a composite plate approximately 3.5 mm thick having a well-adhered copper face, which can be used for making printed circuits, is obtained.

Example F.

Component: a plate of 20 x 20 cm of pre-coated such
obtained in Example 3.

 Conditions: identical to example B.

A plate of identical appearance to that of Example B is obtained.

Example G.

Component: a plate of 20 x 20 cm of pre-coated such
obtained in Example 4.

terms
- heating up to 1500C under docking pressure
- molding under 35 bar at 150 - 1600C for 2 mi
utes,
- post-cooking for 3 hours at 1700C.

An analogous plate of appearance is obtained with that of the example
B.

Example H.

Components: a plate of 20 x 20 cm of pre-coated
obtained under the same conditions as the one used
in example G but in whose composition the
40% slate powder is replaced by 36%
slate and 4% boric anhydride.

 Conditions: identical to those of Example G.

Example I.

Components: a plate of 20 x 20 cm of pre-coated
composition: 10 folds of balanced two-way glass fabric 1581: 77%; resin of
polybismaleimides Kérimid 601 from Rhône-Poulenc: 18%;
alumina trihydrate: 5%, obtained by heating at
1450C and compaction at this temperature under 3 bar
for 30 seconds and demolding at 110 C.

Conditions:
- preheating at 1500C
- molding 3 hours at 1800C or 5 minutes at 2500C under
5 bars.

A plate 2 mm thick is obtained.

Example J.

 Component: a pre-coated plate of the following composition: 10 folds of balanced bi-directional glass cloth 1581: 77%; polystyrylpyridine resin: 18% alumina trihydrate: 5%, obtained under the following conditions: preheating at 2000C under docking pressure, compaction at 2000C under 5 bars.

terms
- preheating at 2200C
molding at 2500 ° C. for 8 minutes under 15 bars
- demolding at 2000C.

A plate 2 mm thick is obtained.

Example K.

Components: a pre-coated plate obtained in
same conditions as that of example 2 but of which
the composition is as follows: PB resin 10: 40%
alumina trihydrate: 40%; carbo fiber mat
do not high module: 20%.

 Conditicns: same as in example B.

The physical and mechanical characteristics of the finished products obtained according to Examples A to K have been studied and the main ones of them are shown in the following table, where the density relative to the water, the modulus of elasticity and the tensile stress in MPa, the resilience in decijoules per square centimeter, and the limit oxygen index in% oxygen (standard
ASTM D 286370).

TABLE N0 1

<tb><SEP> characteristics <SEP> in <SEP> flexion
<tb> Example <SEP> Density <SEP> NF <SEP> T <SEP> 51-001 <SEP> Resiliency <SEP> IOL <SEP>
<Tb>

<SEP> Module <SEP> Constraint <SEP> to <SEP> The <SEP> (Dynsta) <SEP>% <SEP> 2 <SEP>
<tb><SEP> MPa <SEP> break <SEP> dj. <SEP> cm <SEP> (ASTM <SEP>
<tb><SEP> MPa <SEP> NF.T. <SEP> 51-017 <SEP> n <SEP> 286370)
<tb><SEP> A <SEP> 1.40 <SEP> 8400 <SE> 145 <SE> 63 <SEP> 38
<tb><SEP> Bîca? <SEP> 1.84 <SEP> 15000 <SE> 180 <SE> 75 <SEP> 81
<tb><SEP> E <SEP> 1.87 <SEQ> i4400 <SEQ> 195 <SEQ> 75 <SEP> 85
<tb><SEP> F <SEP> 1.88 <SEP> 15000 <SEP> 180 <SEP> 75 <SEP><SEP> 85
<tb><SEP> G <SEP> 1.82 <SEP> 22000 <SEP> 175 <SEP> 18 <SEP> 60.5
<tb><SEP> H <SEP> 1.91 <SEP> 15500 <SEP> 110 <SEP> 22 <SEP>><SEP> 85
<tb><SEP> I <SEP> (b) <SEP> 1.98 <SEP> 21000 <SEP> 490 <SEP> 125 <SEP> 85 <SEP>
<tb><SEP> J <SEP> 2.01 <SEP> 2450 <SEP> 480 <SEP> 132 <SEP>#<SEP> 85 <SEP>
<tb><SEP> K <SEP> 1.66 <SEP> 3200 <SEP> 230 <SE> 72 <SEP> 83
<tb> (a) Characterization of. shaped objects examples C and D did
not done but because of the composition identity
and processing the properties must be substantially iden
to that of Example B.

(b) The interlaminar shear strength of Plate I is
63 MPa.

(c) In the case of Example B, the following are the results of
electrical properties
Electrical properties of the product of Example B
- NF water absorption. C 26150 O, 11%
- Total insulation resistance 11
24 H in (NF C 26150) 1,5,10 ohms
Water at 230C - Loss angle tgg
and dielectric constant (k) 2
at i MHz tgi = 2.1.10
(SEMA LI 1 607) k = 5.1
- Dielectric strength
or breakdown voltage
Conditioning 48 h in water at 500,
breakdown in air: 13 kV; in
50 kV oil.

 It goes without saying that the present invention has been described only as a purely explanatory and non-limiting and that any useful modification can be made without departing from its scope as defined by the claims below.

Claims (7)

 1. Semi-finished products s o u. sformedep 1 aques or blanks based on at least one powdered thermosetting resin, fibrous materials and fillers, characterized in that they have a stable rheological behavior in time and at room temperature, that they contain from 10 to 80% by weight, preferably from 15 to 40% by weight, of a fibrous material chosen from mineral or synthetic fibers in the form of mats, fabrics or wicks, advantageously glass and / or carbon fibers. from 5 to 70% by weight, preferably from 10 to 40% by weight, of a thermosetting resin initially in the pulverulent state and chosen from phenol resins of the Novolac type, aminoplast resins, polyesters, polystyrylpyridines, polybismaleimides, epoxides and the like and from 5 to 60% by weight of a filler selected from active and / or passive inorganic and / or organic fillers in the form of powders, beads or grains such as sand, slate, alumina trihydrate, silica and boric anhydride, these semi-finished products being obtained in semi-co-tin or continuously by introducing into the fibrous structure a powder-based formulation of said thermosetting resin and said fillers, heating to a temperature greater than or equal to the softening temperature of said resin but such that the crosslinking speed remains low, subjecting said resin-filled fibrous structure when said resin is melted at a pressure causing compaction of the formulation and coating of the fibers therewith, hardening of the resulting material by cooling, and storage in the form of strips, plates or blanks.  2. Finished products, in the form of plates or shaped parts resulting from the crosslinking under the action of the previously incompletely crosslinked resin heat present in the semi-finished product according to claim 1 and having a combination of properties adjustable physical properties and in particular a fire resistance of 40 to 100 (expressed as limiting oxygen index according to AST D 286370), a breaking stress of 100 to 500 and more (expressed in Pa according to NF.T-51001 ) and a flexural modulus of 15,000 to 40,000 and over (expressed in next MPa) NF.T 51001).  3. Finished products according to claim 2, characterized in that they comprise one or more superimposed thicknesses of semi-finished products according to claim 1, identical or different in composition and / or size.  4. Finished products according to claim 2, characterized in that the forming and the crosslinking are carried out without cooling the semi-finished product so that the latter still hot, is associated with any other material to give a complex finished product.  5. Finished products according to any one of claims 2 to 4, characterized in that they comprise identical or different coating materials on one or two of the faces of a stack of one or more thicknesses of a semi product. -finished according to claim 1.  6. Products according to any one of claims 1 to 5, characterized in that they: comprise between the layers of semi-finished products according to claim 1, one or more thicknesses of materials of organic or mineral nature serving as a core.  7. Products according to any one of claims 2 to 6, characterized in that they also have good electrical properties, in particular a water absorption of 0.1% at most and a total insulation resistance of 100%. at least 1.5 × 10 1 ohms (according to NF.C-26100 24 hours in water at 23 ° C.); a 1 MHz loss angle (tgS) of at least 2.1.1O2 and a dielectric constant (k) at 1 MHz of not more than 5.1 (according to NEMA standard L. I 160 7); and a breakdown voltage or dielectric strength in air of at least 13 kV and in the oil of at least 50 kV after 48 hours in water at 50 C.