A PROCESS FOR PREPARING A UNIDIRECTIONAL FIBER WEB, THE USE THEREOF FOR PREPARING UNIDIRECTIONAL COMPOSITE MATERIALS

Abstract: A process for preparing a unidirectional fiber web is disclosed, which comprises disposing several rovings side by side, each having a plurality of individual fiber filaments, and needling transversally said rovings, thereby opening the rovings and forming a continuous fiber web therefrom. This continuous unidirectional fiber web can be used for preparing unidirectional composite materials through a wet method.

Description: A process for preparing a unidirectional fiber web, the use thereof for preparing unidirectional composite materials Tπe present invention essentially relates to a process or preparing a jmdirectional fiber weo, a uniαi rectionaι continuous 'ioε ** eo cotaineα therecy, the use thereof for preparing uπiαi rectionaI composite materials and unoi rectionai composite materials cotaineα thereoy. In tre c r i r art, attempts nave oeen maαe tc manufacture u.-πcirect :r,a_ cornccsites containing a .ayer cf umci rectiαπaL * iper Laye 1 " "mpregπateα with a resin. An example cf tnis pπcr art -s JP-Δ-60-< 34A. Howeve.-, tie processes of the prior art are complicated, tf us costly, ana cannot be easily adapted to the preparation of composite materials naving a wioe range cf properties. Therefore, a main purpose cf the present invention is to soive tne tecnnicai problem cf providing a unidirectional fiber weo wnicr, can oe adapted to a wide range cf width, tr.ic ness, ".ecnamcal properties, in a reliable manner. Anotner main purpose cf tne present invention, is to solve tne tecnnicai prcclem cf preparing uniαi rectiona I fiber weos, whic can oe usec --* tne manufacture cf uniαi rectionai composite materials naving wioe mecnanical properties while being aoaoteo to tne manufacture cf said composite materials through a wet process, according to tne traditional paper technology. A furtner main purpose of the present invention is tc soive the tecnnicai prcolem of providing a unidirectional fiber wee, wn cn * ■ s well aαsoteσ tc the manufacture cf laminatea unidirectional composite materials comprising a wioe type cf tπermcplasti r sin and cf reinforcing materials, tnereny -ncreasing tne versatility cf tne use cf said composite materials. ALL ties-* teiT.ical a ro soiv-" <"•". *** -.It * _P O O'!Sι -or tne first time with tne present invention according to a simple, reiiaDie ana low costly solution, wnicn is therefore usable at industrial -εvei, ano nctaoiy in traciticnal caper maxing plants. Thus, in a first aspect, the present invention provides a process for creparing a unidirectional fiber weo comprising disposing - several rovings side by side, each having a plurality of individual fiber filaments, and needling transversally said rovings, thereoy opening the rovings and forming a continuous fiber web therefrom. The continuous fiber weo is obtained through overlapping of filaments of adjacent rovings. According to a specific embodiment, said rovings comprise thousands cf individual continuous fiber filaments bundling together. Accorαing tc another specific embodiment, said needling is performed with hundreds of needles, each needle having an enlarged basis and being provided on the lateral surface thereof with protuberances, such as spikes. According to another specific embodiment, the rovings are continuous fiber glass rovings. Said rovings have preferably a width of some millimetres, for instance about 5 millimetres and the continuous fiber filaments have a diameter ranging between 10 and 50 micrometres, preferably between 15 and 25 micrometres. According to another specific invention embodiment, the needling provides an opening of the rovings from 2 to 6 times the width of the initial roving width. According to another specific invention embodiment, the needling is performed so as to reach a continuous unidirectional fiber web having a weight ranging between 50 and 1000 g/m , more preferably from 500 g/m to 700 g/m . According to a second aspect, the invention also relates to a continuous unidirectional fiber web, which has been obtained from several rovings laid side by side and needled. According to a third aspect, the present invention relates to a process for preparing unidirectional composite material, comprising preparing a unidirectional fiber web and sanαwicmng tnis -.mαi rect ionaI ficer ee cetween at least one rei-vfe-etc trernocias " c sneet tnrcu n a «e; process. Acccrci g to a specific process emooαiment, said reinforced thermoplastic layer is laid en either side cf the unidirectional fiber weo on an inclined wire at the bottom part or at an intermediate part thereof. Typically, the composite structure will be found by sandwiching the aoove-said unidirectional continuous fiber web between two outer layers of reinforced thermoplastic sheets. Acccrαing to another emooαiment, two layers of unid rectional continuous web can be sandwiched between two outer layers cf reinforcec thermoplastic sheets. Of course, many comoinaticns cf sheets can be performed at will. Acccrcir.g to a given emocαiment, the thermoplastic material cf tne re i nforced thermoplasti sneet can be selected from a polyolefine, in particular polyethylene, polypropylene and copolymers thereof, polyvynyl chloride, polystyrene and copolymers, polyamide, saturated polyesters, polyetnylene ether, a polycarooπate and any plastic alloy. A most preferred thermoplastic resin is polypropylene. Preferably, the thermoplastic material is supplemented by a coupling agent which in the final product improves contact between the thermoplastic ana the reinforcing material. Preferred coupling agents are acid or anhydride functionaiized thermoplastics such .as alpha, beta uπsaturated carooxylic acid functionaiized thermoplastics. One such example is maleic or itaconic anhydride grafted polypropylene. The thermoplastic resin is advantageously under powder form having a mean particle size ranging between 200 micrometres and 1,000 micrometres, more preferaoly between 300 and 1,000 micrometres. According to another specific emoooiment, the reinforcing material cf the thermoplastic composite * * s unoer fiber form and is selected f-om glass fibers, carbon fibers, ceramic fibers, boron fibers, g < .a≤s wool, .ΌCK woo., metallic fibers, hot melt organic synthetic fibers, notably aromatic polyamide, polyesters and others. The length of the reinforcing fibers preferably ranges between 5 mm and 25 mm, and the diameter between 5 and 20 micrometers. According to another specific invention embodiment, the reinforced thermoplastic composite sheets are prepared through a wet process according to the traditional paper making technology, from a dilute slurry, preferably having from 0.1 to 5 X by weight dry content, fed preferably onto an inclined wire. According to a most preferred embodiment, the slurry composition, on a dry content basis, of the thermoplastic composite sheet, comprises : thermoplastic resin tinder powder form 40 - 78 X (preferably 45 - 75%, most preferably 49 - 55X) coupling agent 1 - 20 X reinforcing fibers 15 - 40 X dispersant 0.1 - 10 X (with respect to reinforcing fibers) optionally flocculent 0.25 - 1 X anti-oxidant 0.1 - 2 X Optionally, the slurry composition can contain a polyolefine pulp in a content from 2 to 20 X/ According to a specific embodiment, each thermoplastic composite sheet has a basis weight which ranges between 400 g/m 2 and 5 kg/m 2 , and more preferably from 800 to 5000 g/m 2 , and most preferably around 2800 g/m 2 . The general needling conditions of the continuous fiber rovings are as follows : The unidirectional fiber web according to the invention can be prepared from a continuous mineral roving, for instance a continuous fiber glass roving commercially available from Owens Corning Fiberglas Europe under the reference R16 EX3, having a 5 m width, 2400TEX (g/1000 m) , each filament having a diameter of 24 microns. This roving is composed of thousands of individual continuous fiber glass filament bundling together. Additional sizing is added by the fiber glass suppliers so that to ensure these f i laments can stay paneled together. A neeαiir .-.acnine con.-r.e--c * . aι ./ available, for instance from Asseiin -r.acnine, usually seo to prcαuce ncn-woven can typically ce oroviceα with needles supplied by Singer reference 15*18*36/3.5BL 30A610 cf triangular shape with protuberances such as spixes on each sioe cf needle, said needle being held by a holder up to 4 metres wioe. The principle of said needling machine is represented in the appended figures 1 and 2. In figure 1, it is shown schematically the needling machine unαer reference number 10, „hich is fed with a plurality of continuous fiber rovings referenced 12 unrolled from rolls 14. After tne needling, at tne outlet cf the needling machine 10, it is cotainec a continuous unidirectional fiber web 16. In figure 2, it is shown a partial enlarged view of a neeαle 40 with protuberances 42 such as spikes, going through a roving 12 to provide an opened roving naving at le.ast a double width referenced 16a since it is a part of the continuous web 16 cf figure 1. It is understandable that the needling machine consists of hundreds cf needles, each needle having many spikes 42 as shown on figure 2. It is also understandable that wnen the rovings are passed through the needling machine, the up and down motions of the needles serveα to destroy the sizing that binds the filaments together and to comb through the bundled filaments. As a result, the originally bundled filaments are now spread apart as clear from figures 1 and 2. The main factors, which affect how wide the rovings can be opened, 'are the type and sizes of needles, the number of needles per cm , the speed of the machine and the penetration depth of the needles. Generally, the needling conditions are : for the speeα of the machine : 1-40 m/minute, preferably 2 m/minute ; * e nurnce r or r.o i es p uncne rec c f e neec i es ce r z-~ - ; en f e nur **p e r c neeα i es cer z~~ ana t he soeea c f ;ne ~acr 40 tc 150 r.o i es orefe * -ac ι y 60 tσr enc, one cctameo wiαer opening c * - * ovιngs, but ncre c ' reacκage- cf the -- ' Laments) ; - for the penetration cεctr, cf the needle : 10 to 20 mm, pre f eraoiy 25 mm. Unαer these above general conditions, typically 0.5 cm " wiαe roving can oe opened to a 1 to 3 cm wide continuous weo, oreferaoiy " .0 cm. It can ce easily understood that ™ nen a meter wide o i ous weo 15 is needed, preferably 200 rcus 14 cf the 0.5 cm roving "2 3-e used to pass through the needing macnine 10. 'h s is thereby cbtaiπeα a ccntinuous weo 16 having a oas-s e ght rom 50 tc 700 g/m , preferably 500 g/m . New, the general conditions cf preparing the composite sneets are as follows, with reference tc figure 3 for -nstance with regard to the preparation of a sneet having 3 layers, a core or a central Layer 16 maoe with tne unidirectional continuous fiber web as cotainec at the cutlet cf the needling macnine sandwiched two outlet ιaye r s of reinforced thermcpiasti c material referenced 19 anσ 21, whicn are clearly seen on the enlarged cross-section, according tc the lines IV-IV of figure ■-.. Each reinforceα thermociast" c sneet 19 and 21 is obtained through the wet method of the tracit-onai paper making technology from a first head box 18 ana a second head box 20 feeding a slurry containing the composite sheet components in suspension therein onto an inclined wire 30, whicn filtrates water 32 with the aid of a small air depression, as it will be more clearly understood in reference to the following examples. It is easily understandable that ; t is possible tc proαuce more complicated sandwiched structures cy adding further neaσ coxes ana intermediate unid rectional fioer web 16 between the successive neao boxes. Also. it is easily possible to tailor the composite basis weight by adjusting the nature and percentage of the thermoplastic resin, cf the fibers used and the basis weight cf the unidirectional fiber weight 16, which can be itself adjusted as a result of varying the needling conditions . It is for instance possible to produce a composite sheet having a 2400 g/m 2 basis weight with 20 X of unidirectional fiber web 16 having a one centimetre width from 2 x 2400 TEX rovings, and each outer sheets 19 and 21 having a basis weight of 960 g/m 2 with 25 X of chopped fiber glass and 75 X of polypropylene thermoplastic powder, preferably polypropylene powder. Other purposes and advantages of the invention will appear from the following illustrative examples, which are not limited the scope of the invention. In the examples , all parts are given by weight unless otherwise specified. INVENTION EXAMPLE 1 In 7 liters of water containing 2.9 g of a cationic dispersant based on fatty acid (Cartarspers DS1 of Sandox) , 29 g of glass fibers which are sized to have good dispersion in aqueous medium (reference R16 EX25 supplied by Owens Corning * -Fiberglas Europe) having an average length of 13 mm and 16 microns diameter were added with strong stirring. 6 g of synthetic pulp were then introduced with moderate stirring. After suitable dispersion,- -59 g of polypropylene powder, of mean particle size of 700 microns and 6 g of coupling agent (maleic anhydride-grafted polypropylene supplied by EXXON CHEMICAL as EXXELOR 2011) were added. After dilution until the suspension contains about 5 g of solids per liter, the mixture vas then splitted into two streams. Each stream was admitted onto a wire screen 30 through a head box 18 or 20, dewatered then dried according to the conventional paper making technique. A roll of continuous glass web 16 with a basis weight of "-.80 g/m 2 and a width of 28 cm was also laid onto the wire 30 between the first and second head box 18, 20. The arrangement of the head boxes 18, 20 and the continuous glass web 16 feeding is schematically illustrated in figure 3. The composite sheet thus obtained / illustrated in figure 4, had a basis weight of 2700 g/m 2 and comprised sufficient cohesion to be handled, stored, transported and in which the various components of the formulation have been perfectly retained. To make the final industrial product from this sheet, three of such composite sheets may for example be superposed and, after having effected preheating up to a temperature of the order of 180"C to 201"C, the assembly may be moulded under pressures of 40 to 100 kg/cm 2 for a cycle less than 30 seconds. INVENTION EXAMPLE 2 This example differs from the preceding one in that the composition of the slurry contained 2.65 g of dispersant, 26.5 g of fiberglass, 6 g of polypropylene pulpex, 1 g of flocculent, 61.5 g of polypropylene and 6 g of coupling agent. In addition to the compositional change, two rolls of continuous glass web 16 were introduced. COMPARATIVE EXAMPLE 3 This example differs from Example 1 in that the composition of the slurry contained 4.2 g of dispersant, 42 g of fiberglass, 6 g of polypropylene pulpex, 1 g of flocculent, 46 g of polypropylene and 6 g of coupling agent. No continuous glass web 16 was introduced. INVENTION EXAMPLE •* 400 g of the moulded industrial product as described in Example 1 was placed into a infrared oven heated at a temperature of 300-320°C for « * .5 minutes. This well heated product was then transferred to a mould set at 60-80 °C and shaped like a box. The sample was moulded under pressures of 100 to 200 kg/cm 2 for a cycle time of less than 5 minutes. The moulded box was cut into 24 pieces as well known to those skilled in the composite art. Ash content analyzes showed that the minimum and maximum ash contents were 34.17X and 42.56 f. respectively. COMPARATIVE EXAMPLE 5 This example differs from Example 4 in that a competitive sample from Elastogran, Elastopreg B100M45, was preheated and moulded. On close examination of the moulded box, some wall sections are not filled. Data from the examples 1 to 3 are detailed in the table below to illustrate the effect of unidirectional fibers on mechanical properties. Example 1 and 2 contain two levels of unidirectional web, the properties are much higher than comparative Example 3 which contains only random chopped fibers. A competitive sample from Elastogran, Elastopreg B100 M45 , was also analyzed and the properties are shown comparable to our Example 1, except the competitive sample contains 100 X unidirectional fibers versus only 18 X unidirectional fibers in the invention sample. When the sample was highly loaded with unidirectional fibers, poor fiberglass dispersion and incomplete filling of a mould are observed as shown by comparison of invention Example 4 versus comparative Example 5. T A B L E ..', Total glass content '., UD glass content '., Chopped glass content Flexurai modulus Flexural strength Tensi Le s rength Charpy strengt"

Claims: C LA I M S 1. A process ~er preparing a _nιαi rectionai fioer weo comprising disposing several rovings sice by siαe, eacn having a 05 plurality of inoivicual fiber filaments, and needling transversally said ** cvings, thereoy opening the rovings ana forming a continuous fiber weo therefrom. 2. The process of claim 1, wnerein rovings comprise thousancs of individual continuous fiber fi laments bundling 10 togetner. 3. The crocess cf claim 1 or 2, wnerein said needling is performed with hundreds cf needles, each needle having an enlarged oasis anc being provided on the -ateral surface thereof with prctucerances, such as spikes. 15 4. The crocess of any one cf claims 1 to 3, wherein the rovings are continuous fiber glass rovings, having preferably a width of some millimetres, for instance about 5 millimetres and the continuous fiber filaments have a diameter ranging between 10 and 50 micrometres, preferably between 15 ano 25 micrometres. 20 5. The process cf any one of claims 1 to 4, wherein the needling provides an opening of the rovings from 2 to 6 times the width cf the initial roving width. 6. The process of any one of claims 1 to 5, wherein the needling is performed so as to reach a continuous unidirectional •25 fiber weo having a weight ranging between 50 and 1000 g/m., more 2 2 preferably from 500 g/m to 700 g/m . 7. A continuous unid rectional fiber web, wnich has been obtained from several rovings laid side by side and needled, preferably according to the process of any one of claims 1 to 6. 30 8. A process for preparing a unidirectional composite material, comprising preparing a unidirectional fiber weo as defineσ in claim 7 r as obtained by the process of any one of claims 1 to 6, ana sandwiching this unoi rectiona I fiber web between at least one reinforced thermoolast* c sheet through a wet process. 35 9. Tne process cf claim 5, «ner= * n saiα reinforced tnermcpiast c Layer is laid en eιtne r s * αe c * tne unidirect ona l fiber «ec en an -nclir ■ 'nterrrediate part thereof. 05 10. The process of claim 8 or 9, comprising sancwiching the above-said unidirectional continuous ficer weo between two cuter layers cf reinforced thermoplastic sheets. 11. The process of claim 8 or 9, comprising sandwiching two ' layers cf unidirectional continuous weo between two outer layers cf 10 reinforced thermoplastic sneets. 12. The process cf any one cf claims 8 to 11, wnerein the thermoplastic material cf the reinforced thermoplastic sneet is selectee -rcm a polyolefine, in particular polyethylene, polypropylene aπc copolymers thereof, oolyvynyi chloride, ' 5 polystyrene anc copolymers, polya ioe, saturated polyesters, polyethylene ether, a polycarbonate ana any plastic alloy. 13. The process of claim 12, wnerein the thermoplastic resin is unαer powder form having a mean particle size ranging between 200 micrometres ana 1,000 micrometres, more preferably between 300 20 and 1,000 micrometres. 14. The process of any one of claims 8 to 13, wnerein the reinforcing material of the thermopLastic composite is under fiber form ano is selected from gLass fibers, carbon fibers, ceramic fibers, boron fibers, glass wool, rock wool, metallic fibers, hot 25 melt organic syntnetic fibers, notably aromatic polyamide, polyesters and others ; the length of the reinforcing fibers preferably ranges between 5 mm and 25 mm, and the diameter between 5 and 20 icrαmetres. 15. The process of any one of claims 8 to 14, wherein the 20 reinforced thermoplastic composite sneetO are prepared througn a wet process according to the traditional caper making technology, from a dilute slurry, preferably having from 0.1 to 5 '/. by weight ory content, fed preferably onto an inclined wire. 16. Tne process cf c.aim 13, z>r,ere-~ t"e S.JΓΓV composi ion, en a cy cer.tert r α sιs, cf the :~er- ** .ooi5st c composite sneet, comprises : - tnermcpiast ι c resin vr. e" oowoer for~ 05 - coupling agent - reinforcing fibers - dispersant 0.1 - 10 '.' (with respect te reinforcing fibers) - optionally -Hocculent 0.25 - 1 ',.' 10 - anti-exicant 0.1 - 2 '.' - optionally a colyciefine c ic 2 - 10 '. 17. The process cf cairns 8 to 16, * nerein each thermoplast composite sneet has a basis weight which ranges between 400 g/m" and 5 Kg/- *" , and mere preferably from 800 to 5,000 g/m , ' and most 15 preferaciy arouno 2,800 g/m " . 18. Unαi rectionai thermoplastic composite materials as obtained cy the process according to any one of claims 8 to 17. 20 25 30 -5

Inventors: DE RANCOURT HUBERT FRANCOIS MA, THIBAUDEAU JEAN PIERRE, DE RANCOURT, HUBERT, FRANCOIS, MARIE, THIBAUDEAU, JEAN, PIERRE
Applicants: EXXON CHEMICAL LTD, EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL LIMITED, EXXON CHEMICAL PATENTS INC.
Application year: 1991
Main classification: D21H27
IPC codes: B32B5, D04H3, D21H13, D21H27