WO1991017885A1

WO1991017885A1 - Laminate and method for production thereof

Info

Publication number: WO1991017885A1
Application number: PCT/SE1991/000358
Authority: WO
Inventors: Bengt Andersson
Original assignee: Glasis Ab
Priority date: 1990-05-21
Filing date: 1991-05-21
Publication date: 1991-11-28
Also published as: SE9001812D0; SE9001812L; SE466644B; AU7905891A

Abstract

A laminate comprises a layer (5) containing a polymeric material and at least one further layer (6). The latter is formed by a layer of expanded metal, which is at least partially embedded in the polymer material layer. In a process for producing the laminate these layers are pressed together, preferably in connection with heating.

Description

LAMINATE AND METHOD FDR PRODUCTION THEREOF.

FIELD OF THE INVENTION AND PRIOR ART

This invention is related to a laminate comprising a layer containing polymeric material and at least one further layer. Moreover, the invention is related to a process for producing such a laminate according to the precharacterizing portion of enclosed claim 14.

In connection with such laminates it is on one hand desired to obtain a structure having as good a strength as possible. On the other hand it is desirable that the structure of the laminate should be such that the emission of gases, volatile substances, water vapour etc. occurring on curing of the polymeric material may happen relatively rapidly so that the pressing times on production of the laminate do not become burdensome or unreason¬ able from a production technical point of view. The latter aspect is particularly relevant when one or both of the surface layers of the laminate consist of a material impermeable to the cleaving products in connection with curing of the polymeric material, such as tight plastic layers or metal layers.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a laminate and a process for production thereof involving substantial advantages in at least some of the regards discussed hereinabove.

This object is obtained according to the invention by the further layer in the laminate being formed by an expanded metal layer. which is at least partially embedded in the polymer material layer.

Such an expanded metal layer has surprisingly turned out to be associated to considerable advantages in laminates of the nature here in question. From the point of view of strength, the expan¬ ded metal layer is. excellent since it gives the laminate a very good resistance. Due to the uneven topography of such an expanded metal layer, it will be extremely well anchored in the polymeric material also when the expanded metal layer is pressed on to the surface area of the polymeric material layer. It is to be speci¬ fically stressed that an expanded metal layer comprises a netlike structure having net bridges which will be inclined relative to the main plane of the expanded metal layer. Furthermore, expanded metal layers have the advantages that they are constituted of a single coherent material piece, which is a distinction relative to conventional nets, which are produced from interwoven threads.

Due to the netlike structure of the expanded metal layer, it will of course also allow good passage, substantially perpendicularly to the plane of the laminate, of constituents emitted during curing of the polymeric material on production of the laminate. However, one has also been able to establish on practical produc¬ tion tests, that the expanded metal layer in this regard involves advantages also when surface layers impermeable to the emission products are at hand on both external sides of the laminate. More specifically, the occurrence of one or more expanded metal layers in the polymeric material layer between the tight surface layers will cause a substantially improved emission of cleaving products such as gas and water vapour in a direction towards the edge surfaces of the laminate, where the polymeric material layer is exposed. Thus, it seems as though the expanded metal layer simplifies and expedites the discharge along the same so that the pressing times may be shorter and the pressing temperatures higher then when expanded metal layers are not used or when other types of layers are used. Also in this case the cause for the favourable action of the expanded metal layer appears to emanate from its peculiar structure and possibly also from the fact that an individual expanded metal layer is formed by a single material piece. The explanation would appear to be that cavities are obtained in the area of the expanded metal layer due to the fact that the polymeric material is not capable of entirely adjoining to the expanded metal layer all around its inclined bridge portions. These cavities, which are more or less connected in the plane of the expanded metal layer, do accordingly simplify vapour and gas emission. On production of laminates having expanded metal layers on both sides surrounded by polymeric material and externally thereof tight surface layers, it is accordingly suitable that the nature of the polymeric material and the pressing conditions are chosen so that the cavities really are obtained. This is enhanced by locating sheets of polymeric material on both sides of the expanded metal layer in the course of production, said sheets of polymeric material then being pressed against the expanded metal layer and bonded together via the openings of the expanded metal layer without entirely adjoi¬ ning to all surfaces of the expanded metal layer.

Further preferable features of the laminate according to the invention and in addition the features of the process according to the invention are more specifically defined in the claims. In particular, it should be mentioned that especially good proper¬ ties of the laminate according to the invention have been ob¬ tained when the polymer material layer has comprised a composite material containing a curable resin, a fibrous material and a thermoplast. It is then preferred that the thermoplast occurs in the starting composite material in the form of substantially evenly distributed expanded thermoplastic particles.

The term "expanded metal" or "expanded metal layer" used in the application aims at that which is illustrated in Fig 4 in the drawings, namely a netlike metal structure formed by one single coherent metal piece. The expanded metal layer comprises meshes, the width of which may be varied in dependence upon the prevai¬ ling conditions and there are, in the net structure, connecting bridges 1, which will be more or less inclined relative to the main plane of the expanded metal layer. An expanded metal layer of the nature illustrated in Fig 4 is produced in a manner known per se starting from a metal sheet illustrated in Fig 3, said metal sheet being provided with a pattern of suitably mutually displaced and substantially parallel slots 3. This slotted metal sheet is then subjected to stretching substantially perpendicu¬ larly to the longitudinal direction of the slots, i.e. in the direction of the arrows 4, until the structure illustrated in Fig 4 has been obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the enclosed drawings, a more specific descrip¬ tion of embodiment examples of the invention will follow herein¬ after.

In the drawings:

Fig 1 is a diagrammatical cross section through a laminate according to the invention;

Fig 2 is a cross section view similar to Fig 1 but illustrating an alternative embodiment:

Fig 3 is a diagrammatical view illustrating the production of expanded metal; and

Fig 4 is a view illustrating the expanded metal in its final condition.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The laminate illustrated in Fig 1 comprises a layer 5 containing a polymeric material and at least one further layer 6, which is formed by a layer of expanded metal having the basic character illustrated in Fig 4. The expanded metal layer 6 is in the example located in the area of one side of the polymeric layer 5 and partially embedded therein. As can be seen, individual bridge portions 1 in the netlike expanded metal extend obliquely rela¬ tive to the planes of the polymeric layer 5 as well as the expanded metal layer 6.

As illustrated in Fig 1 a surface layer 7 may be provided on that side of the polymeric layer 5 which is opposite to the expanded metal layer. The polymeric layer 5 bonds the surface layer 7 to itself and the latter may for instance be formed by a metal layer, e.g. a sheet or foil of steel or aluminium or alloys thereof. According to an alternative, the surface layer 7 could instead be formed by a layer of plastics or other material. In the case of plastics, it is preferred that the surface layer 7 in itself is formed by a laminate. According to a further alterna¬ tive, an additional expanded metal layer, which is located more or less close to the surface, may be provided instead of the tight surface layer 7. However, said additional expanded metal layer should also be at least partially embedded in the polymer material 5. Thus, one would then obtain a sandwich structure having two expanded metal layers located at the surface and partially exposed outwardly and a polymer core located there¬ between. However, it is to be added that one or more further expanded metal layers could be located between these expanded metal layers located at the surface, said further expanded metal layers then being entirely embedded in the polymeric material. Such interposition of one or more further expanded metal layers could of course also be provided in the polymeric material 5 between the expanded metal layer 6 and the surface layer 7 according to the embodiment illustrated in Fig 1.

In the variant according to Fig 2 the laminate has on both sides of the polymeric material layer 8 substantially tight surface layers 9, e.g. of metal or plastic and between these surface layers, at least one expanded metal layer is embedded in the polymer material layer 8. Thus, two or more expanded metal layers could also here be located embedded in the polymeric material 8 between the surface layers 9. The surface layers 7 and 9 could, if so desired, be formed by perforated layers or otherwise layers provided with holes.

It is preferred that the expanded metal layers 6, 10 are of steel or aluminium or an alloy containing at least one of these metals. The area weight of an individual expanded metal layer 6, 10 is suitably in the range 100-5000 g/m². An area weight in the range 400-1500 g/m² is preferred.

Although the expanded metal layer in Fig 4 is indicated as comprising openings having substantially equally long sides, this is not any requirement. Thus, expanded metal layers having openings with a more or less oblong form may also be used.

It appears from Fig 1 that cavities 11 occur between the poly¬ meric material in the layer 5 and a side, which is turned away therefrom, of the inclined bridge portions 1 in the expanded metal layer. Such cavities 11 are produced if the nature (den¬ sity, compressibility, flow rate etc. during pressing) of the polymeric material and the pressing conditions are chosen for this purpose. The cavities extend into the polymeric material and simplify, accordingly, the emission of products cleaved on curing. The cavities 11 also simplify such emission substantially parallel to the plane of the expanded metal layer 6.

In case of an embedded expanded metal layer (see e.g. the embodi¬ ment according to Fig 2) it is even more important to carry out the laminate production so that also in that case similar cavi¬ ties 11 are obtained. For this purpose it is suitable to make the polymeric material layer 8 composed of two part layers 13 which on their internal sides are bonded mutually in an interface 12 as well as to the expanded material layer 10 and which possibly present the tight surface layers 9 on their external sides. Thus, the cavities are also obtained here due to a suitable selection of the nature of the polymeric material and the pressing condi¬ tions and enhance substantially the gas emission parallel to the plane of the expanded metal layer. The interface 12 between the part layers 13 are of course occurring in the openings of he expanded metal layer. It would, at least in theory, be possible to have the polymer part layers 13, especially when the width of the expanded metal layer 10 in the direction of thickness of the laminate is large, not adjoining to each other or adjoining only over relatively small interface areas 12, in which case the connection of the layers 13 entirely or to a substantially extent, is carried out by the expanded metal layer 10. However, this involves a reduced joining strength, which, however, may be acceptable in certain applications.

The polymer material layer 5, 8 contains at least one cured resin. In that connection it is preferred that the polymer material layer is formed by a composite material containing, in addition to the cured resin, a fibrous material and a thermo¬ plast.

It is preferred that the polymeric composition which is intended to form the polymeric layer 5, 8 is produced as a semi-manufac¬ ture in the form of a foam composite material having the fibrous material in web form, the web-like material being impregnated with the curable resin and the thermoplast and formed into a sheet structure, in which the curable resin exists in B-stage. On pressing of the laminates illustrated, for example, in Figs 1 and 2, one or more such sheet structures are used to form a polymeric material layer 5 and each of the part layers 13 of the layer 8 respectively. Before the press used is closed, one or more such sheet structures are placed between the expanded metal layer 10 and one of the surface layers 9, on production of the laminate according to Fig 2, whereas one or more additional sheet struc¬ tures are located between the expanded metal layer and the remaining surface layer. During a subsequent pressing with application of heat, these sheet structures will be bonded mutually as well as to the expanded metal layer and the surface layers while producing a laminate having an excellent strength. The foam composite material may for instance be produced in the following manner. A pre-condensate of a waterbased curable resin is. produced in a conventional manner and the water contents is regulated so that a dry content of 30 to 75 percent by weight is obtained. The solution obtained in this way is provided with unexpanded thermoplastic particles, so called microspheres, in such an amount that the weight proportion microspheres: resin in the final foam composite material varies between 4:1 and 1:50. It is preferable to allow the microspheres to be included in such an amount that they in an expanded state form 70-95, preferably 85-95, percent by volume of the foam composite material. A webshaped material is impregnated with the mixture of resin and microspheres in a conventional manner, e.g. by moving the web down into a bath of the mixture or by spraying the mixture on to the web. The impregnated web, the degree of inpregnation of which may be regulated e.g. by pressing with rolls, is then subjected to heat, suitably in the form of circulating hot air having a temperature 80-150°C so that the resin cures to B-stage and the microspheres expand. In this connection it should be pointed out that a cureable resin, which is in A-stage, is meltable, cross linked to a small degree and soluble in acetone and other sol¬ vents. A resin in C-stage is unmeltable, entirely cross linked and insoluble. The B-stage is a stage between the A- and C-sta- ges.

The cureable resins, which preferably come in question are formed by so called formaldehyde-based resins with carbamide, phenol, resorcinol or melamine. However, cureable resins may also be used more generally, such as polycondensated resins, e.g. polyi ide and polyadded resins, e.g. polyuretane.

The web shaped material may be formed by a woven or non-woven, organic or inorganic material, amongst which glass fibre, mineral fibre, cellulose fibre, polyester fibre may be mentioned in particular. It is also important that the web shaped material has a sufficient porosity to be able to be impregnated with the mixture of resin and microspheres in a satisfactory manner. Furthermore, the web shaped material should not be too thick, and the thickness may suitably vary between 0.1 and 5 mm. The reason why the web shaped material must be thin is that one otherwise risks obtaining an uneven expansion of the microspheres since the peripherical microspheres on supply of heat expand first and then form a heat insulating layer, which prevents the more centrally located microspheres from expanding, and in such a case one obtains a non-homogenous product of a worse quality.

The microspheres used on production of the foam composite mate¬ rial according to the invention have shells which may be formed by copolymers of vinyl chloride and vinylidene chloride, copoly¬ mers of vinyl chloride and acrylonitrile, copolymers of vinyli¬ dene chloride and acrylonitrile, and copolymers of styren and acrylonitrile.

Furthermore, copolymers of methyl methacrylate should be mentio¬ ned, which contain up to about 20 percent by weight styrene, copolymers of methyl methacrylate and up to about 50 percent by weight of combined monomers of ethyl methacrylate, copolymers of methyl methacrylate and up to about 70 percent by weight of orto chlorostyrene. The particle size of the unexpanded spheres and, accordingly, of the expanded spheres may vary within wide limits and is chosen with guidance by the properties, which are desired of the final product. As an example on particle sizes for unex¬ panded spheres one may mention 1 μm to 1mm, preferably 2 μm to 0,5mm and in particular 5 μm to 50 μm. The diameter of the microspheres increases on expansion with a factor 2-5. The unexpanded spheres contain volatile liquid expanding agents, which are evaporated on the application of heat. These expanding agents may be formed by freons, hydrocarbons, such as n-pentane, i-pentane, neopentane, butane, i-butane and other expanding agents, which conventionally are used in microspheres of the nature here defined. The expanding agent may suitably form 5-30 percent by weight of the microsphere. The microspheres may be added to the resin solution as dried particles or in a suspension e.g. in an alcohol, such as methanol. The proportion resin to microspheres in the impregnation solution may, as has previously been pointed out, vary .within wide limits and this proportion affects the properties of the final product. Conversely, one can, accordingly, choose a suitable relation resins to microspheres in the mixture starting from a certain field of use and certain desired properties of the final product. This proportion may easily be determined by preparatory experi¬ ments in laboratory scale.

The mixture of resins and microspheres may, if so desired or required, be provided with various additives, such as stabili¬ sers, coupling agents, fillers, fire retarding additives and/or pigments.

The foam composite material present as a sheet structure may for instance have an area weight within the range 40-10 000 g/m .

When producing the laminates according to e.g. Figs 1 and 2, the required number of sheets consisting of the foam composite material and the expanded metal layers occurring and possible surface layers are combined and the combination is pressed as an elevated temperature. The pressing time, temperature and pressure are substantially chosen with regard to the type of resin and microspheres used and of course with regard to the actual type of laminate. The time for the pressing may often vary between 20 seconds and 30 minutes. The temperature may vary between 100 and 200°C and the pressure between 0.01 and 3 MPa. If the laminate aimed at does not have any particular surface layers, particular¬ ly attractive effects may be obtained by the "free" surface, i.e. the surface turned towards the press plate, of the foam composite material becoming entirely smooth since the microspheres adjacent to the press plate may be caused to collapse by the press force if the same is suitably chosen. However, when particular surface layers are used is may be suitable to choose such conditions that the expanded microspheres do not collapse. It is to be mentioned that it is not necessary to use a fibrous material in web or fabric shape. Thus, the fibrous material of organic or inorganic origin, e.g. glass fibre, mineral fibre, cellulose fibre, polyester fibre, could be dispersed in the polymer composition used for producing the polymer layers 5, 8.

On production of the laminates according to e.g. Figs 1 and 2, the surface layers, when being of metal, may have an area weight between 100 and 20 000 g/m². When using surface layers of plas¬ tics material, these may have a thickness between 0.05 and 5 mm. The plastic surface layers may be formed by prefabricated sheets or sheetlike elements, such as formaldehyde-based high pressure sheets or high pressure layers and polyester-based sheets and layers. Combinations of various curable plastics may of course be used for the surface layers.

Non-limiting examples on production of the foam composite mate¬ rial as a semi-manufacture and laminates according to the inven¬ tion follow hereinafter:

Example 1

A glass fibre felt of 50 g/m² is impregnated with a dispersion of VDC/ACN microspheres from KemaNord AB and the fenol resin solu¬ tion 9916 from Casco, having a dry content of 60%, where the dry content relation is MS:PF 2:1. (VDC = vinylidene chloride, ACN = acrylonitrile, MS = microspheres, PF = Phenol formaldehyde resin) .

After dipping into the impregnation bath, the excess is pressed away by means of rolls. The felt is subsequently treated with air at 120^βC, water being expelled until a residual moisture of 7 percent by weight remains and at the same time the microspheres expand. The sheet product obtained is suitable to be used for the polymer layers 5, 8 in the laminates according to Figs 1 and 2 in the desired number, laminate pressing being carried out at 0.25 MPa and 125°C for 10 minutes. The polymer layer obtained is formable in itself at a temperature of about 120°C.

Example 2

A process as in example 1 but with the relation MS:PF 1:1 counted on the dry contents.

Example 3

A process as in example 1 but with the relation MS:PF 1:2 counted on dry contents.

Example 4

A laminate having the structure appearing from Fig 1 was produced by applying in a press a plate of an aluminium alloy and having an even thickness of 1 mm and in addition an expanded metal layer of untreated aluminium and having meshes 20 x 10 mm. The area weight of the expanded metal was 1 300 g/m². A polymer composi¬ tion containing a phenol resin, glass fibre (comprising 25 percent by weight of the composition) and expanded thermoplastic particles, so called microspheres, evenly distributed in the composition was applied between the aluminium plate and the expanded metal layer. The composition has suitably the character of the sheet like foam composite material described above and present as a semi-manufacture. The area weight of the polymer composition was 850 g/m .

Pressing together was then carried out at the temperature 150°C, the pressure 0.5 MPa and for a time of 3 minutes, which gave an intimately joined laminate having a thickness of 5.5 mm.

The laminate had a rigidity vastly exceeding a homogenous alumi¬ nium plate having a corresponding total weight. Laminates according to the invention have excellent properties as far as fire resistance and heat insulation are concerned and can easily be machined by punching, bending and other forming opera¬ tions without breaking the foam polymer layers 5, 8. The lami¬ nates according to the invention have excellent properties for use as a building and construction element in a variety of situations where a good strength and/or attractive surface is required. Use as surface forming layers in buildings and vehicles may be mentioned as examples.

The laminates described and the process for production thereof may of course be varied in many ways within the scope of the invention.

Claims

1. A laminate comprising at least one layer (5, 8, 13) containing a polymeric material and at least one further layer, c h a r a c t e r i z e d in that the further layer comprises a layer of expanded metal which is at least partly embedded into the polymeric material layer.

2. A laminate according to claim 1, c h a r a c t e r i z e d in that it on at least one side of the polymeric material layer comprises a substantially tight surface layer (7, 9).

3. A laminate according to claim 2, c h a r a c t e r i z e d in that the surface layer (7, 9) comprises a metal layer.

4. A laminate according to claim 2, c h a r a c t e r i z e d in that the surface layer (7, 9) comprises a plastic layer.

5. A laminate according to any of claims 2-4, c h a r a c t e r i z e d in that the expanded metal layer (6, 10) is arranged at or adjacent to that side of the polymeric material layer which is opposite to the substantially tight surface layer (7) .

6. A laminate according to claim 1, c h a r a c t e r i z e d in that expanded metal layers are arranged at or adjacent to the two opposite sides of the poly¬ meric layer.

7. A laminate according to any of claims 2-4, c h a r a c t e r i z e d in that substantially tight surface layers (9) are arranged on its two external sides and that at least one expanded metal layer (10) is embedded in said at least one polymeric material layer (8, 13) between the surface layers.

8. A laminate according to any preceding claim, c h a r a c t e r i z e d in that cavities (11) exist between the polymeric material and portions of the expanded metal layer.

9. A laminate according to any preceding claim, c h a r a c t e r i z e d in that the expanded metal layer (6, 10) is of steel or aluminium or an alloy containing at least one of these metals.

10. A laminate according to any preceding claim, c h a r a c t e r i z e d in that the area weight of the expan¬ ded metal layer is in the range 100-5000 g/m² , preferably 400-1500 g/m².

11. A laminate according to any preceding claim, c h a r a c t e r i z e d in that the polymeric material layer contains at least one cured resin.

12. A laminate according to claim 11, c h a r a c t e r i z e d in that the cured resin is a formal¬ dehyde-based resin, preferably a phenol resin.

13. A laminate according to claim 11 or 12, c h a r a c t e r i z e d in that the polymeric material layer is formed by a composite material comprising, in addition to the cured resin, a fibrous material and a thermoplast.

14. A laminate according to claim 13, c h a r a c t e r i z e d in that the thermoplast is in the form of expanded particles.

15. A process for producing a laminate comprising at least one layer (5, 8, 13) containing a polymeric material and at least one further layer (6, 10), the laminate being obtained by pressing, preferably in connection with heating, c h a r a c t e r i z e d in that an expanded metal layer is used as the further layer (6, 10) and that the expanded metal layer on pressing is embedded at least partially in the polymeric material layer.

16. A process according to claim 15, c h a r a c t e r i z e d in that a polymeric composition containing a curable resin, a thermoplast and a fibrous material is used as a starting material for production of the polymeric material layer.

17. A process according to claim 16, c h a r a c t e r i z e d in that a formaldehyde-based resin, particularly a phenol resin, is used as the curable resin.

18. A process according to claim 16 or 17, c h a r a c t e r i z e d in that the thermoplast exists in the polymer composition in the form of expanded thermoplastic partic¬ les, which preferably are substantially uniformly distributed in the polymer composition.

19. A process according to any of claims 16-18, c h a r a c t e r i z e d in that the polymer composition has been produced as a semi-manufacture in the form of a foam compo¬ site material having the fibrous material in web form, the web form material having been impregnated with the curable resin and the thermoplast and formed into a sheet structure, in which the curable resin exists in B-stage, and that one or more such sheet structures are used on pressing of the laminate.

20. A method according to any of claims 15-19, c h a r a c t e r i z e d in that the nature of the polymer material and the pressing conditions are adjusted so that cavi¬ ties (11) occur between the polymer material and portions of the expanded metal layer.