GB2114572A - Bituminous/plastics insulating material - Google Patents

Abstract

Insulating material comprises expanded plastics beads encapsulated in bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents. The expanded beads are encapsulated in the bitumen or compound while the latter is in liquid form in a hot process. The encapsulated beads are subsequently pressed together and distorted to form a body with voids between the beads substantially eliminated. The main advantages of the invention are that the resultant body is stronger and more water resistant than those bodies which have previously been obtained.

Description

SPECIFICATION Insulating material The present invention relates to an insulating material comprising expanded plastics beads which are each completely encapsulated in bitumen or a bituminous compound, and to a method of manufacture thereof.

Materials are in principle known, for instance from British Patent Specification 1,592,096, which comprise expanded polystyrene beads covered with bitumen of low softening point, together with an emulsifier.

Also proposed have been materials according to British Patent Specification 1,344,235 where again an emulsified bitumen is used to coat expanded polystyrene beads in a volume ratio of about 1 to 6.

According to the present invention there is provided an insulating material comprising expanded plastics beads which are each encapsulated in bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents, such encapsulation having been formed with the bitumen or compound in liquid form in a hot process.

The present invention also provides an insulating material in the form of a body comprising expanded plastics beads which are each encapsulated in bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents, such encapsulation having been formed with the bitumen or compound in liquid form in a hot process, the encapsulated beads having been subsequently pressed together and distorted to form a body with voids between the beads substantially eliminated.

Further, the present invention provides a method of making an insulating material by heating bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents to a temperature appreciably above its softening point in order to make it liquid and free running and processing expanded plastics beads therewith so as to completely encapsulate each of the beads.

The present invention also provides a method of making an insulating material body by heating bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents to a temperature appreciably above its softening point in order to make it liquid and free running and processing expanded plastics beads therewith so as to completely encapsulate each of the beads, and, while the encapsulating bituminous material is in a semiliquid state, pressing the beads together and distorting them so as substantially to eliminate voids betwen the beads.

By a semi-liquid state we mean that the bitumen or compound is hot enough to be tacky but not hot enough to be runny.

One consequence of the feature of the invention that the bitumen or bituminous compound applied to the beads is free from solvents, light oils, emulsifiers and the like is that the coating can be waterproof. For in stance, if an emulsifier is used, there is a risk that in the presence of water the emulsion will revert back to the liquid phase and thus not provide a waterproof coating. A problem with using solvents for bitumen, of course, is that they tend also to be solvents for expanded plastics beads, and this is also avoided with the present invention where the encapsulation of the individual beads is of better continuity and water tightness, and the material, whether in the form of beads or of a body, is therefore useful in situations where water or damp may occur without the beads taking up the moisture.

In addition, insofar as the prior art has contemplated the use of expanded polystyrene beads covered with low softening point bitu men, these suffer from the major disadvan tage that the presence of hot sunshine or elevated temperature will soften the bitumen and any assembly of such coated beads will lose its cohesive strength.

Particularly useful results can be achieved if the bitumen or bituminous compound used has a softening point significantly greater than the melting point of the beads, e.g. by 10 to 20 C or more, and if it is solid at ambient temperature so that after encapsulation cooled beads can readily be separated and remain separated without mutual adherence.

Preferably the plastics beads are of polysty rene, preferably in the form of expanded poly styrene spheres, in which case they have a melting point of about 95 to 100 C. The bituminous compound is preferably an asphalt and preferably has a softening point of at least 11 5'C (Institute of Petroleum Needle Method). In one preferred embodiment the asphalt is heated to 1 85 C during the encap sulation process. Preferably the bitumen or bituminous compound has a penetration value of 1 to 6, preferably 1 to 4, at a conditioned temperature of 25 C.

When the insulating material is in the form of a body it may have a continuous hard and smooth surface. This can be achieved by the step of applying a heated surface over all surfaces of the body, which will generally be in the form of a board.

The step of pressing the encapsulated beads together to form a body can be per formed between moving endless belts, on a table using a reciprocating roller, by passing the material on a moving belt beneath a roller or by simple compression. Preferably, how ever, the beads are cooled after encapsulation, separated from each other, and reheated when pressed together so that the encapsulat ing material becomes sticky or tacky, but not runny. It is also possible for satisfactory re sults to be obtained when the beads are further expanded, or re-expanded, while being pressed together so as to be urged against one another and interlock with and have substantially straight edges between one another.

Preferably such further or re-expansion is brought about by the injection amongst the beads of superheated steam at between 1 50 C and 1 80 C. As an indication of appro private further expansion, which can be due to pentane or other gases retained within the heads, it can be mentioned that in a preferred case the initial volume ratio of beads to bitumen is between 25 and 30 to 1 and the final volume ratio is approximately 40 to 1. Preferably the beads pass in a covergent run between endless belts, while expanding outwards towards the belts. This arrangement has the advantage of improving uniformity of b-ad size in the finished product, and excluding voids thus making the body more strong both flexurally and in compression.If mere external compression were relied on, beads near the surface would tend to be squashed, while those near the middle would not be to such an extent, so as a weaker product would result. The use of hot steam and the material becoming tacky in the present invention aids adhesion when the bitumen cools.

It is possible and preferred to obtain bodies according to the invention with flexural strength of 30-45psi (2.10-3.15kg/cm2) measured according to B.S. 4370 and compression strength of 1 5-25psi (1.05-1.75kg/cm2) at 25 C and 20% compression.

A preferred feature of the invention concerns the proportions of bitumen or bituminous compound to beads. Preferably, at the mixing stage, the volume of beads is at least 20 times the volume of bitumen or compound, and while the ratio can extend from 20 to 1 up to at least 50 to 1, a preferred range is 25 to 40 to 1. As a result, the volume of weight ratio of the product, whether in the form of a body or in the form of individual encapsulated beads, is high, which is clearly most acceptable in an insulating material where the insulating effect increases with volume. The weight ratio is preferably aproximately one part by weight of beads to one-and-a-half parts by weight of bitumen or bituminous material.

In order to ensure that all beads are, so far as possible, encapsulated with bitumen or compound it is also referred to keep the aggregate surface are of the beads relatively low. This can be done by using beads of not less than a certain size, preferably 2mm, and by ensuring that the beads do not include "fines", the presence of which would greatly increase surface area with negligible increase in volume. Thus it is preferred that the diameter of the smallest beads is not less than one fifth, and generally not less than one half of the diameter of the largest beads, while most advantageously the beads are of substantially uniform size. Thus beads of from 2 to 10, preferably 3 to 6mm in diameter are preferred. There are particular advantages in uniformity and strength of end product if the size distribution of the beads is kept small.

In the case of bodies according to the invention which are boards, desirable thicknesses are between 3 to 10cm, typically 5cm and in other dimensions the board size can be selected as desired but it is envisaged that boards of say 60 x 1 20cm will prove particularly useful for ease of manufacture, storage, handling and installation.

It is, of course, very surprising that in the method of the invention beads can be successfully encapsulated by bituminous compound, which is hotter than the melting point of the beads, Such, however, is the case.

Initially, before encapsulation, the beads will tend to be coherent due to static charges built up on them but is has been found that when they are added to the hot bitumen the bitumen immediately forms itself into a thin coating all around and one each bead. The beads will not individually accept more than this minimum coating, which provides complete encapsulation, and excess bitumen is passed from one bead to another in a remarkable way. Thus, on the addition of the beads to the mixer containing hot bitumen, the bitumen spreads itself in a most unexpected way so as entirely to encapsulate each bead with bitumen or compound. In a short time all beads are encapsulated, i.e. entirely covered with bitumen.The result of this is that the static forces initially holding the beads together are destroyed although thereafter the bitumen tends to hold the beads together, after cooling, or at least initial cooling, occurs in the mixer.

The invention extends to the beads encapsulated with the bitumen or compound in loose form. On discharge from the mixer any adherence caused by the bitumen or compound can be removed by a gentle vibratory operation. The result is an aggregate of waterproofed, exceedingly light and buoyant insulating beads which are useful in situations where buoyancy is desired because the beads cannot absorb water even after prolonged immersion. In certain insulating applications, for instance in filling cavities with insulating material, such beads may be exceedingly useful.

In embodiments comprising bodies such as boards the cooled mix, or the mix while cooling, is removed from the mixer and then as previously described pressed to such an extent that voids between the beads are substantially removed, i.e. the beads deform but their volume will not be substantially changed, and indeed is preferably increased due to additional heating and blowing. Com pression of a heap of loose beads to about 2/3 thickness is normally sufficient, though greater compression increases the possibility of absolutely all voids being removed. One object of the pressing step is that there should be no path through the board formed by interconnected voids. This permits maximum board thickness, and thus the maximum insulating effect, for a given weight of material.

Another object is that the beads should so press one upon its neighbours, that they become distorted and interlocked, contacting one another along straight lines as the material is viewed in section. This confers high flexural and compressive strength to the resultant board. Thus, when this is done the resulting board is waterproof, substantially void free and in fact a structure of considerable strength and very little weight. The boards and bodies can if desired be further improved by the surface treatment previously described, which is in effect an "ironing" treatment whereby a heated surface is passed all over each surface of the board.This softens the bitumen, and to some extent melts beads which are on the surface and the result is a hard, durable, smooth, handleable and abrasion resistant surface which increases the waterproofness and surface hardness of the panels and ensures that each always remains individually sealed.

Bodies of the invention, by reason of the very small quantities of bitumen or bituminous compound used, remain exceedingly light but are nevertheless robust and offer excellent insulating possibilities. At least some of the possible applications of the bodies and boards will be obvious, for instance in building, in roofing or walls where a heat insulating function is obtained in a most convenient and consistent way. Because they can be factory produced quite easily, and are convenient for stacking and handling they will be exceedingly easy and cheap to transport and to install accurately.

In order that the invention may be more clearly understood the following description is given by way of example only with reference to the accompanying drawings, in which: Figure 1 is an illustration of a cross section of a sample of solid material according to the invention; Figure 2 is a schematic view of apparatus used in performing the method of the invention in making a solid insulating material according to the invention.

Shown in Fig. 1 is a drawing to full scale of a cross section cut through a sample of material 10 according to the invention. The white areas such as 11 represent beads and the black lines bounding them are the asphaltic encapsulating coating 12. Attention is particularly directed to the fact that there is notable uniformity of bead size through the section, that is to say the beads are not noticeably smaller near the edges than they are in the middle. This is brought about by heating and further or re-expansion of the encapsulated beads in the body forming step. Another feature to be noted is the absence of voids between the beads. This uniformity leads to relatively low bead surface area which means that a minimum of bituminous material is required in order to provide a satisfactory waterproofing encapsulation of each bead, and adhesion of the beads to each other.

As shown in Fig. 2 the plastics beads are initially deposited in a mixer 15 which already contains bitumen or bituminous compound in softened form, preferably asphalt at 1 85 C, so that the compound fully encapsulates all beads. The beads are partially cooled, tipped onto a conveyor 16 for further cooling, passed under a roller 17 to separate them and make them discrete, and then fed to a hopper. At this point the encapsulated beads constitute a material according to the invention. From the hopper the beads are fed at a controlled rate onto the lower of two endless belts 21. An upper belt is shown at 22. The belts 21, 22 converge over a first part of their run and then extend parallel to one another. Extending into the space between the belts are tubes 24 to convey superheated steam to the region of the beads.Due to pentane or other gases retained in the beads, these will expand further when heated, ensuring that pressure exists within the material throughout its thickness as it is formed, and not merely near its edges due to the convergence of the belts. Shown at 25 and 26 are supply rolls of plastics sheet to cover the endless belts 21 and 22 and corresponding take-up rolls for these plastics sheets are provided at the other end so as to prevent the material adhering to the endless belts. The body is formed in the converging part of the run between the belts, and the downstream parallel parts of the run are chilled to cool the thus formed body.

The solid materials of the invention which thus comprise encapsulated polystyrene beads compressed together comprise a weather resistant insulating board which is able to withstand continuous rainfall without taking up moisture and thus retaining its thermal efficiency as an insulator. Moreover, the preferred use of a high softening point bitumen which is solid at ambient temperature means that there is no fear of failure in the construction of the material in hot weather or hot climates.

As a result the material can be installed as a thermal insulation for instance for flat roofs and it can be installed above the normal roof waterproofing layer. This allows the waterproofing layer itself to be installed at its most effective position which is directly onto the roof deck and it also provides protection of the waterproofing layer against extremes of temperature and ultraviolet light so that the life of that layer is itself extended significantly.

In addition, of course, the material of the invention provides exceedingly favourable insulation properties in a strong, easy to handle, form.

Claims (39)

1. An insulating material comprising expanded plastics beads which are each encapsulated in bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents, such encapsulation having been formed with the bitumen or compound in liquid form in a hot process.

2. A material according to claim 1, wherein the beads are free-flowing, the bitumen or bituminous compound being solid at ambient temperature.

3. An insulating material in the form of a body comprising expanded plastics beads which are each encapsulated in bitumen or bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents, such encapsulation having been formed with the bitumen or compound in liquid form in a hot process, the encapsulated beads having been subsequently pressed together and distorted to form a body with voids between the beads substantially eliminated.

4. A material according to claim 3, wherein the bitumen or bituminous compound is solid at ambient temperature.

5. A material according to claim 3 or 4 which has a smooth outer surface.

6. A material according to claim 3, 4 or 5, wherein the beads are so distorted from spherical form as to interlock with and have substantially straight edges between one another.

7. A material according to claim 3, 4, 5 or 6 which has a flexural strength of 2.10-3.1 5kg/cm2 and a compression strength of 1.05-1.75kg/cm2 at 25 C and 20% compression.

8. A material according to any preceding claim, wherein the diameter of the smallest beads is not less than one fifth, and preferably not less than one half of the diameter of the largest beads.

9. A material according to any preceding claim, wherein the beads are generally of uniform size.

10. A material according to any preceding claim wherein the softening point of the bitumen or bituminous compound is higher than the melting point of the beads.

11. A material according to any preceding claim, wherein the bitumen or bituminous compound is an asphalt with a softening point of 11 5 C or more (Institute of Petroleum Needle Method).

12. A material according to any preceding claim, wherein the bitumen or bituminous compound is an asphalt which has a penetration value of 1 to 6, preferably 1 to 4, at a conditioned temperature of 254C.

13. A material according to any preceding claim, wherein the beads are of polystyrene.

14. A material according to any preceding claim, wherein the weight ratio is approximately one part by weight of beads to oneand-a-half parts by weight of bitumen or bituminous material.

15. A material according to any preceding claim in which the beads are from 2 to 1 Omm in size.

16. A material according to any preceding claim, wherein the beads are from 3 to 6mm in size.

17. A material according to any preceding claim, wherein the volume ratio of beads to bitumen or bituminous composition is from 25 to 1 to 40 to 1.

18. A method of making an insulating material by heating bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents to a temperature appreciably above its softening point in order to make it liquid and free running and processing expanded plastics beads therewith so as to completely encapsulate each of the beads.

19. A method according to claim 18, wherein the bitumen or bituminous compound is solid at ambient temperature and the beads are separated one from another once coated so as to be free-flowing.

20. A method of making an insulating material body by heating bitumen or a bituminous compound which is free from solvents, light oils, emulsifiers or other liquifying agents to a temperature appreciably above its softening point in order to make it liquid and free running and processing expanded plastics beads therewith so as to completely encapsulate each of the beads, and, while the encapsulating bituminous material is in a semiliquid state, pressing the beads together and distorting them so as substantially to eliminate voids between the beads.

21. A method according to claim 20, wherein the bitumen or bituminous compound is solid at ambient temperature.

22. A method according to claim 20 or 21, wherein the beads are cooled after coating, separated from each other and reheated when pressed together.

23. A method according to claim 20, 21 or 22, wherein the beads are further expanded or re-expanded while being pressed together so as to be urged against one another and interlock with and have substantially straight edges between one another.

24. A method according to claim 23, wherein the further expansion is brought about by the injection amongst the beads of superheated steam at from 150 C to 180 C.

25. A method according to claim 23 or 24, wherein the initial volume ratio of beads to bitumen is between 25 and 30 to 1 and the final volume ratio is approximately 40 to 1.

26. A method according to any one of claims 20 to 25, wherein the beads are pressed together while passing along a convergent run between endless belts.

27. A method as claimed in claim 26 including the step of providing plastics sheets to move with the belts in said run to avoid the material adhering to the belts.

28. A method according to any one of claims 20 to 27 including the step of applying a hot flat surface to the body to provide a smooth surface thereon.

29. A method according to any one of claims 18 to 28, wherein the diameter of the smallest beads is not less than one fifth, and generally not less than one half of the diameter of the largest beads.

30. A method according to any one of claims 18 to 29, wherein the beads are generally of uniform size.

31. A method according to any one of claims 18 to 30, wherein the softening point of the bitumen or compound is higher than the melting point of the beads.

32. A method according to any one of claims 18 to 31, wherein the bitumen or bituminous compound is an asphalt with a softening point of 115 C or more (Institute of Petroleum Needle Method).

33. A method according to any one of claims 18 to 32, wherein the bitumen or bituminous compound is an asphalt which has a penetration value of 1 to 6, preferably 1 to 4, at a conditioned temperature of 25 C.

34. A method according to claim 31, 32 or 33, wherein the asphalt is heated to a temperature of 185"C.

35. A method according to any one of claims 18 to 34, wherein the beads are of polystyrene.

36. A method according to any one of claims 18 to 35, wherein the weight ratio is approximately one part by weight of beads to one-and-a-half parts by weight of bitumen or bituminous material.

37. An insulating material substantially as hereinbefore described.

38. A method for forming an insulating material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

39. An insulating material made by the method of any one of claims 18 to 36 or 38.