GB2260100A

GB2260100A - Surface-reinforced thermoplastic plate and processes for producing it

Info

Publication number: GB2260100A
Application number: GB9219454A
Authority: GB
Inventors: Claude Dehennau
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 1991-09-16
Filing date: 1992-09-15
Publication date: 1993-04-07
Anticipated expiration: 2012-09-15
Also published as: GB2260100B; FR2684595A1; BE1005387A3; DE4231008A1; ES2040663B1; IT1255363B; GB9219454D0; ES2040663A1; ITMI922122A1; ITMI922122A0

Abstract

A thermoplastic plate 2 is reinforced with sections of a tape 1 which consists of an assembly of parallel continuous fibres impregnated with a thermoplastic. The tapes are positioned symmetrically on both faces of the plate, the distance between two neighbouring sections of tape, on each face of the plate, being at most equal to four times the width of a section of tape. In the figure only plates B, D, F, G, K exemplify the invention. The reinforced plate can be produced by injection moulding or by thermoforming under compression and exhibits an improved rigidity. One application is for a vehicle trim unit. <IMAGE>

Description

?,7! r 1 ', t 1 _ 1 t Surface-reinforced thermoplastic plate and processes

for producing it The present invention relates to thermoplastic plates reinforced at the surface by sections of a tape consisting of a group of parallel. continuous fibres impregnated with a thermoplastic, and to simple processes 5 for producing such plates.

By the term plate the Applicant intends to denote not only plates but also any planar or profiled elongate article whose thickness, not necessarily uniform, can vary between 1 and 20 mm and more.

It is well known at present to produce ribbons or tapes consisting of a group of parallel continuous fibres impregnated with a thermoplastic. Such products and their production method are described especially in European Patent EP-B-274,464 and in British Patent GB-1,259,085.

In particular, these products can be advantageously employed for producing, by winding. hollow and elongate articles such as pipes, which have remarkable mechanical properties.

The Applicant has envisaged using sections of such tapes for surface-reinforcing thermoplastic plates when they are moulded, but has found that the reinforced plates thus obtained generally tend to distort when being demoulded.

After numerous disappointing attempts the Applicant nevertheless succeeded in producing reinforced plates which no longer tend to distort when being demoulded.

The present invention consequently relates chiefly to a plate made of optionally filled thermo- plastic surface-reinforced with sections of a tape consisting of a group of parallel continuous fibres impregnated with a thermoplastic. which is char"acter"aed in that the sections of tape are positioned symmetrically on both faces of the plate, the distance between two neighbouring sections of tape, on each face of the plate, being at most equal to four times the width of the said sections of tape.

It has been found, in fact, that when the conditions set out above are met it is possible to obtain reinforced plates of excellent qualities and exhibiting mechanical properties, in particular a flexural stiffness, which are remarkable.

The thermoplastic constituting the plate may be of any kind and, to give an example, vinyl, olefin, acrylic and similar resins may be mentioned in particular.

The thermoplastic impregnating the sections of tape is preferably chosen as a function of that constituting the plates. It is preferable, in fact, that these thermoplastics be compatible and can adhere firmly together under the effect of heat. In a preferred embodiment the thermoplastics constituting the plates and those impregnating the tapes are identical.

The continuous fibres embedded in the sections of tape can be of any kind and are chosen as a function of the required mechanical properties. By way of examples there.may be mentioned vegetable fibres, synthetic fibres and inorganic fibres such as glass, metal, carbon, ceramic, quartz and similar fibres, inorganic fibres and, in particular, glass fibres being frequently preferred.

The sections of tape may be of any length whatever which depends on the size of the plates, and their cross-section is generally rectangular. The width of the sections of tape may vary between 0.5 and 5 cm, a larger width not being ruled out, and their thickness may vary between 0. 1 and 1 cm, it being possible for a greater thickness to be envisaged in special cases.

As a general rule the sections of tape are arranged on both f aces of the plate in parallel to one of its edges. However, an oblique arrangement of some or all of the sections of tape is not excluded by any means. Similarly, in the plate in accordance with the invention some of the sections of tape can be arranged parallel to an edge of the plate and the remainder parallel to the 1 5h 1 1 adjacent edge of the plate.

The plate in accordance with the invention can also be reinforced on one or both of its faces with additional sections of tape arranged symmetrically to 5 each other between neighbouring sections of tape.

The plate in accordance with the invention can finally be subsequently covered, on one or both of its faces, with a film of any coating whatever so as to mask the sections of tape, should this be found necessary.

The plate in accordance with the invention is, furthermore, illustrated by Figure 1 of the attached drawings, in which various possibilities are shown with regard to the arrangement of the sections of tape 1 on a thermoplastic plate 2 shown in cross-section.

In this figure the alternative forms of arrangement A, C, E, H, I, J and L, which do not f orm part of the scope of the invention, result in plates which distort during the demoulding, whereas the alternative forms of arrangements B, Di F, G and K, which do form part of the scope of the invention, result in plates which do not distort.

In particular, the alternative forms A, C, E, H and L do not obey the condition of symmetry on both f aces of the plate, the alternative form E additionally does not obey the condition of maximum distancing between the neighbouring symmetrical sections of tape, and the alternative f orms 1 and J do not obey the condition of symmetry on one face in the case of additional sections of tape.

The invention also relates to processes for producing economically a reinforced thermoplastic plate as described above.

According to a first process the plate is pro duced by the injection moulding technique.

In this case the sections of tape are provision ally attached beforehand to the walls of the injection mould cavity before it is closed with a view to the moulding of the plate.

The provisional attachment of the sections of tape can be obtained in particular using double-faced adhesives arranged at the ends or over the whole length of the sections of tape. It has. in fact, surprisingly been found that such a method of provisional attachment is sufficient to prevent any undesirable displacement of the sections of tape during the subsequent injection moulding operation. After cooling and demoulding of the plate the double-faced adhesives can be easily pulled away from the moulded plate. It is quite obvious, however, that other methods of provisional attachment can be envisaged without departing thereby from the scope of the present invention.

It has been found that when the abovementioned technique is employed the sections of tape adhere perfectly and definitively to the surface of the plate. Such a result is astonishing in itself since, in principle, the thermoplastic constituting the sections of tape placed in contact with the molten thermoplastic injected into the mould does not reach a sufficient temperature to melt.

According to a second process, which can be advantageously exploited when the plate is intended to be subjected to a thermoforming treatment, use is made of this operation to produce the plate in accordance with the invention.

In this case, the sections of tapes are provi sionally attached beforehand to the walls of the thermo forming moulds.

According to an alternative embodiment which can be advantageously employed in this latter process, at least some of the sections of tape can be arranged on the thermoplastic plate or while it is being preheated with a view to its thermoforming.

The reinforced plate in accordance with the invention and processes for producing it are, further more, illustrated in the examples of practical embodi ments which will follow and in which reference will be 7 made in particular to Figure 2 of the attached drawings, which shows, in diagrammatic cross-section, a device for thermoforming using compression. Example 1 A plate in accordan e with the invention is produced from Eltex P HY202 trademark polypropylene using the injection moulding technique. Eltex P HY202 is a polypropylene marketed by the Applicant. A Battenfeld BMT 240 injection press and an 10 injection mould for plates 350 x 110 mm in size with a thickness of 3 mm are employed for this purpose. The sections of tape employed for reinforcing the plate have a length of 295 mm and are cut from a tape with a width of 10 mm and a thickness of 0.4 mm, consist15 ing of a group of continuous and parallel glass fibres impregnated with Eltex P HY202 polypropylene, the fibre content of the tape being 50 % by weight. In order to produce a reinforced plate according to the variant K of the attached Fig. 1, 10 sections of 20 tape are attached in the appropriate places on the walls of the open injection mould cavity, maintained at 3CC, this being done with the aid of a doublefaced adhesive tape. After closure of the mould, thus lined, the 25 molten polypropylene is injected, the set temperatures of the 10 control zones of the extruder being 200-200-200200-200-200-240-250-255 and 255C respectively and the set temperature of the channel conveying the melt towards the mould being 255C. After cooling and opening of the injection mould a reinforced plate is obtained which does not exhibit any tendency to distortion. Furthermore, after pulling away the double-faced adhesives it is found that the sections of tape have not been displaced in any way in the mould 35 during its filling and that they are embedded, in the appropriate places, in both surfaces of the plate, the adhesiveness being beyond reproach.

Finally, should it be found necessary, the outward appearance of the plate reinforced in this way can be substantially improved by applying a coating film to one or both of its faces, it being possible in particular for such a f ilm to be applied by the coinjection technique.

Example 2

In this example, which refers- to Fig. 2, a reinforced internal trim unit is produced by thermo- forming under compression, for a rear shelf of a motor vehicle.

A plate 6 produced from a 50-50 mixture of polypropylene and wood sawdust and marketed by the company G.O.R. Applicazioni Speciali S.p.A. under the registered trademark Wood Stock. is used for this purpose.

Four parallel sections 7 of a tape according to Example 1, 2 mm apart, are attached, in predetermined places and by means of a double-faced adhesive, to the edge away from the points of attachment of the plate to the vehicle and to the upper surface of the plate, and the plate thus lined is then introduced into a conven tional oven, not shown, with a view to being preheated to the thermoforming temperature.

Four parallel sections 5, also 2 mm apart, of a tape according to Example 1 are then placed, in approp riate and predetermined places, on the lower cavity 3 of a mould for thermof orming under compression, the securing in place being also ensured using a double-faced adhesive.

The preheated plate 6 is then positioned between the cavities 3 and 4 of the thermoforming unit, which are maintained at 250C, so that the sections of tape 5 and 7 are arranged facing each other, a finishing lining 8 consisting of a textile supported by a frame 9 being arranged between the preheated plate 6 and the upper cavity 4.

The thermoforming of the plate under compression is then carried out using the traditional method.

After demoulding, a rear shelf unit is obtained which is reinforced with symmetrical sections of tape 5 and 7 on the profiled edge away from its points for attachment.

It is found, in addition, that the finishing lining 8 perfectly masks the sections of tape 7 and that the visible face of the trim unit thus produced conse quently does not show any unaesthetic defect.

It is found, finally, that the visible sections of tape 5 adhere perfectly to the trim unit.

A trim unit thus obtained is subjected to a flexural test between supporting points and under a load of 4 kg at 800C and a central sag of 7 mm is found after 96 hours.

In comparison, a trim unit which is identical but not equipped with sections of tape 5 and 7 is subjected to the same test and a central sag of 60 mm is found 20 after 96 hours.

It therefore appears that the trim unit obtained according to the process of the invention exhibits a markedly improved rigidity.

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Claims

C L A I M S

1 Plate of optionally filled thermoplastic surf ace reinforced with sections of a tape consisting of a group of parallel continuous fibres impregnated with a thermo plastic, characterised in that the sections of tape are positioned symmetrically on both faces of the plate, the distance between two neighbouring sections of tape, on each face of the plate, being at most equal to four times the width of the said sections of tape.

2. Thermoplastic plate according to Claim 1, characterised in that it additionally comprises, on one or both faces, additional sections of tape arranged symmetrically to each other between neighbouring sections of tape.

3. Thermoplastic plate according to Claim 1, characterised in that the thermoplastic employed for impregnating the tape is chosen so as to be compatible with the thermoplastic constituting the plate.

4. Thermoplastic plate according to Claim 1, characterised in that the thermoplastic employed for impregnat- ing the tape is identical with the thermoplastic constituting the plate.

5. Thermoplastic plate according to Claim 1, characterised in that it is subsequently covered on one or both of its faces with a coating film.

6. Process for producing a surface-reinforced thermoplastic plate according to any one of Claims 1 to 5, characterised in that the plate is produced by moulding in an injection mould and in that the sections of tape are provisionally attached beforehand to the walls of the injection mould cavity.

7. Process for producing a surface-reinforced thermoplastic plate according to any one of Claims 1 to in which the thermoplastic plate i-s intended to be subjected to a thermoforming operation between moulds, characterised in that the sections of tape are provisionally attached beforehand to the walls of the thermoforming moulds.

1 9

8. Process for producing a surface-reinforced thermoplastic plate according to Claim 7, characterised in that at least some of the sections of tape are arranged on the thermoplastic plate before or while it is being preheated with a view to thermoforming.

9. A thermoplastic plate substantially as hereinbef ore described, with reference to the drawings.

10. A process for producing a surface-reinforced thermoplastic plate substantially as hereinbef ore described, with reference to the examples.