JPH0514615B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION This invention relates to dimensional heat recoverable articles and methods of manufacture. A recoverable article is an article that substantially changes its dimensional shape when subjected to heat treatment. Typically, upon heating, these articles recover to their original shape before being deformed; however, as used herein, the term "heat recoverable" refers to the recovery of the new shape even if it has not been previously deformed. It also includes articles that take In its most common form, such articles consist of heat-shrinkable sleeves made from polymeric materials exhibiting elastic or plastic memory, such as those described in U.S. Pat. . For example, U.S. patent no.
As clarified in No. 2027962, the initial dimensionally heat-stable shape may be obtained by a continuous process, such as expanding an extruded tube while hot into a dimensionally heat-stable shape. may be a temporary shape, but in other cases, a preformed dimensionally heat-stable article is transformed into a dimensionally heat-stable shape in another step. When manufacturing heat recoverable articles, the polymeric material may be crosslinked during any step in the manufacture of the article that enhances the desired dimensional recovery. One method of making heat recoverable articles is to form the polymeric material into the desired heat stable shape and then crosslink the polymeric material to form the article, depending on the type of polymer, at a crystalline melting point or for amorphous materials. The process consists of heating the article to a temperature above its softening point to deform the article, and cooling the article in that state to maintain the deformed state of the article. In use, the article in the deformed state is thermally unstable and will tend to assume its initial thermally stable shape upon application of heat. Other methods involve deforming a substantially uncrosslinked polymer at a temperature below the crystalline melting or softening point of the material to combine one or more material articles and at least one polymeric component into at least one hollow heat recoverable material. It consists of crosslinking the substantially uncrosslinked material after shaping the article. In other articles, the elastic member is held in a stretched state by a second member and heated to soften the member and restore the elastic member. In an article of this type, described for example in GB 1440524, an outer cylindrical elastic member is held in tension by an inner cylindrical member. Heat recoverable articles are known to be very useful for environmentally protecting long substrates, such as communications cable connections. In addition to providing environmental protection, the sleeve is required to withstand internal pressure. This is because the complete connection enclosure is subjected to pressure tests for leakage, as for example in Bell Cycle and Britain Telecom instructions, or because the temperatures reached during use can create significant internal pressures. It is. Although known thermally recoverable sleeves are quite suitable for the conditions encountered in power distribution connection enclosures, many larger communications cables are internally pressurized to exclude moisture.
Sleeves with thicker wall thicknesses that are required to withstand such pressures for long periods of time are more difficult to manufacture, more expensive and require greater skill to install. In U.S. Pat. No. 3,669,157 and Japanese Patent Publication No. 53-13805, it has been proposed to provide heat-shrinkable tubular fabric articles impregnated with certain thermosetting resins. However, the articles disclosed therein were found to be very difficult to install because they caused migration of the resin during recovery, resulting in the resin rupturing the fabric or causing the resin to fall off the fabric. Therefore, these prior art articles have limited utility and are very technical to use in many communications applications. In accordance with one aspect of the invention, the invention provides a dimensional heat recoverable article having a composite structure comprising a heat recoverable fabric and a polymeric matrix material, comprising: (a) the heat recoverable fabric, when heated; (b) the polymer matrix material has a recovery stress (Y) of at least 5 x 10 ^-2 MPa at a temperature above its recovery temperature; At temperatures above, the polymer matrix material has an elongation at break greater than 20% and a secant modulus (X) of at least 10 ^-2 MPa (measured at a pull rate of 300%/min).
, and This is a related part. ] Provided is a heat-recoverable article, characterized in that it has an elongation/temperature profile such that the temperature at which ? is less than 1 is at or above the recovery temperature of the fiber. The present invention also provides a method for manufacturing a dimensionally heat-recoverable article having a composite structure which is recoverable due to a recoverable fiber component, the method comprising: a heat-recoverable fabric as defined above; A method comprising bonding such polymeric materials as a matrix is provided. The term "fiber" as used herein means
It includes filaments, such as monofilaments or multifilaments, and also staple fibers, wires and tapes. The fabrics used in the articles of the invention preferably employ heat-shrinkable fibers in the form of filaments, especially monofilaments. The heat recoverable fibers used in the articles of the invention are preferably 10 ⁻¹ MPa, more preferably 5×
It has a minimum recovery stress of 10 ⁻¹ MPa and usually at least 1 MPa at temperatures above the transition temperature of the fiber. Theoretically there is no upper limit to the recovery stress, but in practice it is 200 MPa, and more generally the highest value normally achieved by polymeric fibers is 100 MPa. The fibers are preferably formed from a polymeric heat recoverable material. "Recovery temperature" of a polymeric heat recoverable material means the temperature at which substantially complete recovery of the polymeric material is achieved. Generally, the recovery temperature is the crystalline melt transition temperature if the polymer is crystalline, or the glass transition temperature if the polymer is amorphous. In many forms of articles of the invention, the polymer matrix softens at a temperature below the recovery temperature of the heat recoverable fibers so that the matrix material has the required elongation and secant modulus and equation (1) The temperature (T) below 1 is the same as the recovery temperature of the fiber. The present invention, however, also encompasses the case where the rigid matrix material holds the fibers against recovery in a temperature range above the recovery temperature of the fibers and then softens to allow the fibers to recover. Preferably, the heat recoverable fibers are formed from a polymeric material that provides the fibers with good physical properties and particularly good creep resistance. Olefin polymers such as polyethylene and ethylene copolymers, polyamides, polyesters, acrylic polymers and other polymers are used, preferably polymers that can be crosslinked. Particularly preferred polymeric materials for the fibers include 0.94-0.97 g/
It is based on polyethylene with a density of cc, a weight average molecular weight (Mw) of 80×10 ³ to 200×10 ³ and a number average molecular weight (Mn) of 15×10 ³ to 30×10 ³ . Preferably the recovery temperature of the fiber is 60°C or higher, most preferably 80-250°C, e.g. 120-250°C.
The temperature is 150℃. When fibers are crosslinked by radiation, it is convenient to incorporate a crosslinking step into the manufacture of the fibers. The fibers are extruded and drawn at a temperature below their melting point, preferably at a rate of 800 to 2000%, and then irradiated to effect crosslinking. Another less preferred method of producing fibers is to extrude the fibers,
It consists of irradiating to crosslink, then heating the fiber, preferably above its melting point, to draw the fiber, and then cooling the drawn fiber. The high density polyethylene fibers are preferably irradiated with a dose of about 5 to 35 Megarads, more preferably about 5 to 25 Megarads, most preferably about 7 to 18 Megarads, especially 10 to 18 Megarads. Typically, the gel content of the crosslinked fibers is greater than 20%, preferably greater than 30%, and most preferably greater than 40%. In practice, gel contents greater than 90% are not easily achieved. Fibers produced in this way can have high strength even after recovery. Other advantages of irradiating fibers are discussed below in connection with lamination. The heat-recoverable fabric can be made solely of heat-recoverable fibers as described above, or can include other fibers in addition to the heat-recoverable fibers, if desired. If the fabric contains such other fibers,
R in the above formula (1) relates only to the heat-recoverable fiber component. The fabric may be knitted, woven, non-woven, or braided. The recoverable fibers may be part of the fabric itself when it is made, or they may be additional and inserted after the base fabric has been produced. In a preferred embodiment, the fabric is woven. The woven fabric may include only heat recoverable fibers or may include heat recoverable fibers along with non-heat recoverable fibers or filaments. Fabrics include, for example, twill, broken twill, satin, sateen, leno, plain weave, hops weave, satin and combinations of various weaves, single or multiply weave, e.g. May be woven into a 3-ply weave. Preferably the cloth is
It is a woven fabric having heat-shrinkable fibers in one direction and dimensionally heat-stable fibers in the other direction, so that the fabric as a whole is recoverable in only one direction. The following description therefore generally refers to such fabrics. However, the features described also apply to other fabrics. On the other hand, the fabric may be knitted if desired, and may be warp-knit or weft-knit. If the fabric is made of heat-recoverable fibers alone, it is recoverable in two directions, but if the fabric is made of heat-recoverable fibers and heat-stable fibers, which is preferred for knitted fabrics, If knitted, recovery is only possible in one direction, whether warp or weft insertion. The average effective volume fraction of heat-recoverable fibers in a composite structure along a given direction depends, among other things, on the fiber dimensions, the type of weave or knitting, and the direction considered. In this specification, the average effective volume fraction R used in the above equation (1) is calculated by multiplying the cross-sectional area of each heat-recoverable fiber by the vector component of the fiber in a predetermined direction, and calculating the cross-sectional area perpendicular to the direction under consideration. It is defined as the sum of the values divided by the total cross-sectional area of the composite structure taken on a plane, averaged along the direction of consideration. Therefore, if a heat-recoverable fiber is present at an angle α to the considered direction, the product of the cross-sectional area of the fiber and its component in the considered direction is:
It is given by woven fiber area x cosα. The sum of this value for all fibers cut by planes perpendicular to the direction under consideration, divided by the total area of the composite structure, gives the R value at a particular point along the direction under consideration. The average value of the R value over the entire length of the relevant fabric section in the direction under consideration is used in equation (1) above and in claim 1. In the case of weaving where all the heat recoverable fibers are parallel to each other (warp or weft in the case of weaving) and the direction under consideration is parallel to the recoverable fibers (i.e. recovery direction), The average value of R is given by dividing the total cross-sectional area of all recoverable fibers by the total cross-sectional area of the composite structure. The heat recoverable fabric is preferably bonded to, and more preferably embedded in, the polymer matrix material. The advantages of irradiation already mentioned above appear here. If before or after forming the fibers into cloth,
If irradiated (especially in the presence of oxygen),
Chemical changes occur on the surface that significantly improve the bonding of the matrix material. At or above the recovery temperature of the fibers, the polymeric matrix material should be capable of limited flow under pressure, such that the matrix material substantially blocks the fibers. Retains the integrity of composite structures without physical recovery.
Preferably, the polymeric matrix material has a temperature of greater than 50%, more preferably
Elongation at break greater than 100%, especially 400-700%
and preferably has a 20% secant modulus of at least 5×10 ⁻² MPa, more preferably at least 10 ⁻¹ MPa (measured at a tensile rate of 300%/min). Although the specified properties of the polymer matrix material do not necessarily have to be applied after recovery, it is desirable that the product be flexible at room temperature. Thus, for example, the polymer matrix material may be subsequently cured and heat set by heating. However, the cure rate must be slow enough under the recovery conditions to not adversely affect the aforementioned physical properties of the polymer matrix material during fiber recovery. Thus, for example, the polymer forming the matrix material may contain hydrolyzable grafted silane groups that can subsequently crosslink the material in the presence of moisture. on the other hand,
The matrix material may contain a polymer, preferably a rubber and especially an acrylic rubber, the rubber containing an epoxy group and a curing agent that is insoluble at room temperature, such as dicyandiamide. The polymer matrix material can be either thermoplastic or elastomeric. in general,
It is desirable that the polymer matrix material and the recoverable fiber material be chemically or physically compatible, and more preferably chemically and physically compatible. This means that both are of similar or the same chemical type and that the relevant physical properties of both are similar or the same during lamination, installation and use. In particular, it is desirable that the matrix and fibers be low density polyethylene and high density polyethylene, respectively. Additionally, other compatible polymer pairs can be selected by those skilled in the art. Examples of thermoplastic materials suitable as matrix materials include ethylene/vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, polyethylene (including linear low density and high density), polypropylene, polybutylene, polyester, polyamide, Mention may be made of polyetheramides, perfluoroethylene/ethylene copolymers and polyvinylidene fluoride. If we consider the second class of materials, this includes acrylonitrile-butadiene-styrene block copolymers, acrylic elastomers and copolymers thereof, including acrylates and methacrylates,
For example, polybutyl acrylate, and poly2-
Ethylhexyl acrylate, vinyl acetate and ethylene copolymer (VAE), polynorbornene,
Included are polyurethanes and silicone elastomers. The polymeric material forming the matrix is transparent (at least to visible light),
Alternatively, it may be completely opaque, or it may have any opacity between these two extremes. If the opacity is increased, for example by blending a small amount (not more than about 5% by weight) of carbon black into the matrix, the time required for recovery appears to be shorter.
Also, the resistance of the material to thermal damage, especially flame thermal damage and UV damage, is reduced. The matrix material (or a portion thereof) may be crosslinked, for example a crosslinked ethylene/vinyl acetate copolymer, linear low or high density polyethylene or acrylic elastomer. The material can be crosslinked by irradiation or other means such as chemical crosslinking (e.g. chemical crosslinking using peroxide crosslinkers).
It can be crosslinked by However, the physical properties of the matrix at the recovery temperature are specified after the crosslinking step. If irradiation is used, doses of 10 megarads or less are preferred, especially doses of 3 to 7 megarads. The degree of crosslinking obtained thereby makes it possible to recover the matrix along with the fibers, especially during thermal recovery using a torch, and also to prevent the matrix from moving or falling during thermal recovery. The recovery rate of the composite material after irradiation is at least 50%, in particular at least 70%, compared to before irradiation These lines are considered typical for olefinic polymers, e.g. polyethylene at low irradiation, but the person skilled in the art It is then possible to select the dose appropriately depending on the different concentrations of prorad that may be present. Composite structures can be manufactured using a single irradiation if the matrix and fiber beam responses are made comparable. The oriented fiber beam response was increased by the addition of Prorad,
The beam response of less oriented matrices is reduced by the addition of antirad. Otherwise a separate crosslinking step is desirable.
Another property of post-lamination crosslinking (particularly irradiated crosslinking) is that crosslinks are formed in the recoverable fibers and/or between other fibers present, thereby making the structure a true composite. This helps to preserve the structure, especially under harsh recovery conditions. This may eliminate the need for physical interengagement, allowing less stringent lamination methods to be employed. The heat-recoverable fabric is preferably bonded to the polymeric matrix material; this bond may be adhesive, ie physical or chemical surface interaction or also mechanical interengagement may be provided. Most preferably, the heat recoverable fabric is embedded within a polymeric matrix material, thereby forming a composite structure. This “buried”
means that the polymeric matrix material surrounds at least a major portion of the surface area of the fibers making up the fabric. Although the fibers are preferably completely surrounded by the polymeric matrix material, it is possible, and sometimes desirable, for substantially less than the entire fiber surface area to be surrounded by the polymeric matrix. This is possible if a fiber-matrix bond is formed. Sufficient fiber area must be bonded or interengaged with the polymeric matrix material to provide a composite structure that retains the integral structure during recovery of the article. For the purpose of disambiguation, the term matrix refers to a material that (partially or completely) surrounds the fibers and also a material that simply rests on the surface of the fibers but does not penetrate into the fiber lattice. It also includes. Preferably, the polymer matrix material is substantially unstressed, at least on the surface of the composite structure facing the heat source, and (as described in British Patent Application No. 8300217) at least 0.03mm, especially at least 0.01mm,
Furthermore, it has a thickness of at least 0.2 mm, for example 0.2 to 2 mm. This is because it improves the ability of the composite structure to be heat recovered using a conventional propane torch. In a composite structure, the ratio of the volume occupied by the heat recoverable fibers of the fabric to the total volume of the composite structure is at least about 0.01:1, preferably about
0.1:1 to about 0.8:1, more preferably about 0.2:1 to about
The ratio is 0.4:1. In composite structures, the volume of heat recoverable fibers in a given composite structure unit volume is dependent on the strength of the fibers, the strength of the polymer matrix, and the integrity of the fiber/polymer matrix structure at recovery conditions. where an acceptable recovery product has the formula: (both values at a temperature T higher than the recovery temperature of the fiber). R is the average effective volume fraction of heat recoverable fibers in the composite structure. ] was found to be obtained when is less than 1. Preferably, X/Y (1-R)/R is less than 0.5, more preferably less than 0.5. Composite structures can be formed, for example, by laminating one or more layers of polymeric matrix material to a heat recoverable fabric. Sufficient heat and pressure is preferably applied to cause at least a major portion of the fabric to bond to, or create a sufficient amount of mechanical interengagement with, the polymeric matrix material. In this way,
The result is a composite structure that recovers as a unit when heat is applied. The method of bonding the fibers to the matrix is as follows:
For example, impregnation, solution coating, slurry coating, powder coating, reactive prepolymers (eg acrylic prepolymers activated by ultraviolet light or peroxides) can be employed. In any bonding method, an amount of heat that will cause the fabric to recover should not be applied unless appropriate measures are taken to prevent the fabric from recovering. The heat recoverable articles of the present invention can be used in many applications. It is particularly suitable for enclosing long substrates such as pipes, conduits, cables, etc. A layer of a sealant or adhesive composition can be applied to the surface of the heat recoverable article.
The sealant may be a mastic and the adhesive may be a heat activated adhesive such as a hot melt adhesive. Hot melt adhesives that can be used include polyamide and ethylene/vinyl acetate copolymer based adhesives.
Such adhesives are known, see for example US Pat. Nos. 4,018,733 and 4,181,775. If desired, thermosetting adhesives may be used (see for example GB 2104800). Proper selection of the polymer matrix material allows the polymer matrix material to function as an adhesive to secure and seal the recovered composite structure to the substrate. The fabric may be embedded in one or more polymeric matrix materials to impart desired properties. For use in enclosing long substrates, each surface of the fabric can be laminated with a layer of matrix material, with the surfaces that will be inward facing in use laminated with a polymeric matrix material with adhesive properties. , while the outer surface may be laminated with a matrix material. As will be readily apparent, the matrix material may be selected depending on the inherent and other desired properties of the polymeric material itself, or may include various other desired properties, such as antioxidants, UV stabilizers, pigments, anti-tracking agents, etc. Additives may be supplied. The heat recoverable article of the present invention is typically a sheet, but may have any other shape, such as a tube. The tube shape also includes a structure in which a large number of tube-shaped portions are mutually continued, such as a branched structure. This branch structure is used where a cable is connected to one or more other cables, or where two or more pipes are connected together. The heat recoverable sheets of the present invention can be used to form cable connection cases, pipe segments or pressure vessels (see GB Patent Application No. 8300221). The heat recoverable article of the present invention has been found to be particularly suitable for use in enclosing connections between pressurized communication cables. The recovered article is surprisingly resistant to the effects of pressure, and preferred embodiments are impermeable and approximately
It has sufficient hoop strength to be able to withstand 70 KPa pressure conditions (a typical pressure used in pressurized communication systems) and against rupture at the operating temperatures of such systems. When forming cable connection cases, the sheets of the invention are used with some type of internal support, such as a generally cylindrical liner with a tapered end. Preferably, the liner is shaped such that: its larger central portion fits around bulky cable connections, and its tapered ends meet at the transition where the dimensions reduce to the cable. Compatible. The liner may be of the wrap-around type, in which case the liner preferably consists of halves with a crown or other end support, or a rigid liner wrapped around the cable connection. The crowned end may again provide an end support member. This end support member is secured with tape onto the cable. In this method, a pressure vessel is formed around an object (such as a cable connection), the sheet material provides an impermeable creep-resistant and tear-resistant enclosure, and the liner Meet impact resistance, axial strength and other mechanical requirements. Certain other configurations may be added if the connection case or pressure vessel is intended to hold pressure during use rather than simply pressure testing for integrity prior to use. Valves on other pressure access points are usefully supplied with resilient seats,
Furthermore, it may be added to the inner liner.
Fabric-based seats are well suited for feeding valves or other instruments that must pass through the seat. This is because tearing is less likely to occur. Even if a fiber breaks during insertion of the bulb, the damage will not propagate and, if care is taken, a hole for the bulb can be created by simply pushing apart adjacent fibers. A second characteristic desired in a pressurized connection case is some means of preventing any bond between the outer sleeve and cable from being separated by internal pressure. A satisfactory result is to provide surfaces such that one surface engages (preferably couples) the cable and the other surface engages (preferably couples) the sleeve, thereby allowing the two surfaces to open. Obtained using strips of material with The strip of material preferably has a U-shaped or V-shaped cross section and is mounted on the re-entry side facing the connection case. Other uses for composite structures include communications, high voltage,
It encompasses the environmental protection, repair or insulation of a wide range of substrates in the electronic, oil and gas, and manufacturing industries. For example, in addition to manufacturing cable connection cases, we also manufacture cable jackets for their high strength and
Repairs can be made by installing new composite materials, which have significant advantages due to their flexibility and corrosion resistance. It is also possible to protect the pipes from corrosion or other damage, in which case the coating of sealants, especially mastic, on composite structures is desirable. Pipe insulation can also be formed using composite structures, in which case certain other insulation materials, such as foam materials, can also be used, if desired. Thermal and/or electrical insulation can also be provided. Another use of composite structures is in the production of hollow articles that serve as housing and protection for a wide range of elements. Yet another use for composite structures is in securing two or more articles, such as pipes or cables, to a long substrate. If the pipe or cable must be secured under very adverse conditions, some type of tight and environmentally resistant securing is required. One particularly important example of such an application is the protection of electrical wiring running along the outer surface of a helicopter rotor blade girder. In some cases, electrical wiring may need to run along the outer surface of the girder of the rotor blade before passing through the blade. For example, such wiring is used to power heating elements located along the leading edge of the blade to prevent ice formation of the blade. In this example, the wires are held along the surface of the girder by restoring the heat-recoverable article of the present invention thereon. Fabric recovery articles have been found to be particularly suitable for this application due to their relatively high abrasion resistance which prevents or reduces damage that can occur from exposure to the elements. In addition, the relatively strong forces exerted on the substrate by the attached heat recoverable article prevent or reduce any movement of the electrical wiring due to centrifugal or other forces that occur when the blade is in operation. be able to. Furthermore, the fact that the fabric article has a relatively high tear resistance makes it possible to restore protrusions on girders such as nuts and bolts. A helicopter rotor blade is supported by a girder that is attached at one end to the rotor blade gearbox. A number of heating pads are located along the leading edge of the rotor blades to prevent ice formation on the blades, and power is supplied to the heating pads along a wiring harness. First, a heat-shrinkable wraparound composite structure is restored over the portion of the girder over which the harness extends to hold the harness rigidly on the girder. Preferably,
The composite structure is formed from laminated heat shrinkable fabrics in which the laminated polymer layers are unirradiated and the recovery ratio of the composite structure is approximately 2:1. Of course, it is possible to irradiate the stacked layers or to vary the recovery rate. Preferably, the cover is formed as a wraparound article and is supplied with a rail-channel type fastening device. On the underside of the cover, a hot-melt adhesive, such as an ethylene/vinyl acetate copolymer-based or polyamide-based adhesive, is provided to secure the cover to the girder and prevent water ingress along the harness. good. Depending on the use of the cover, it may be desirable to cover the entire surface of the cover with adhesive or to cover the excess along the edges with adhesive. For many applications, the resilient composite structures of the present invention are preferably made in an open shape, such as a tube. The sheet is easy to manufacture in this way and is also easy to install since there is no need to access the free edge of the substrate to be surrounded. However, one of the problems that arises here is how to secure the sheet in a wrapped shape around the substrate. What is needed is some means of securing the recoverable fibers at opposite ends of the sleeve together. Solutions can be broadly divided into four categories. The first is to provide a wrap or other bond between opposite ends of the sheet, in which case a patch may optionally be used to prevent separation of the overlapping ends during recovery.
In this case, the bond is generally formed between the matrices at opposite ends, so care must be taken to ensure that the restoring forces of the fiber are properly transferred from the peel to the matrix at its ends. Second
, some means of penetrating the sheet is used;
In this case, the fabric is used directly. Generally, this technique is not possible with continuous sheet materials because of tearing problems. However, the resistance to tearing of fabric-based materials is very high. Examples of this type of fastening include the use of pre-inserted fasteners such as stitches, staples, rivets, press-studs, or multiple fasteners placed adjacent to the lap joint of the sheet and penetrating both thicknesses of the sheet. The use of means with protrusions is included. This second form is described later in more general terms.
A third broad type of fastening involves connecting the opposing ends together by some type of fastening means, such as a C-shaped channel or a reusable device. It is to form a part. This is accomplished by bonding material to the edges or by folding the edges themselves (possibly around rods extending along the length of the sheet). The resulting end of the sleeve will therefore have a similar shape to the rail of a rail-channel fastening as disclosed in GB 1155470. A fourth technique to be described involves forming the fabric in a double fold without terminating in opposite ends where the recoverable fibers are connected. An example is the use of a recoverable weft on a shuttle loom and the insertion of a surrounding member between the weaves at each end or the use of special selvedges. Other possibilities are to weave a closed pocket at each end, or to weave into a tube structure, flatten the tube and then insert a sealing rod or other member into the flattened tube. It is used as a sheet that can be applied. Although these techniques are described using the term woven, they can be applied mutatis mutandis to other fabrics, such as braids and knits. Some of the encapsulation techniques described above are described in UK Patent Application No.
Described in No. 8300223. When the recoverable sheet of the present invention is used in a wraparound configuration, it is desirable to use flaps under the opposing ends that are brought together. Such a flap may be integral with the seat;
Improves environmental sealing and pressure retention if necessary. The second technique for holding a sheet in a wrap-around configuration as described above will now be described more generally. Since the resilient composite structure can be penetrated, it is thereby possible to form hollow articles of various shapes, not only tube shapes, but also hollow articles of various shapes, such as bends and T-joints, or simply It is also possible to form separate branches as cylindrical articles. Therefore, generally speaking, two or more parts of a composite structure can be connected together using a mechanical connection device that penetrates the fabric. Preferably, the connecting device is one or more staples. The connected portions may be discontinuous or separate portions of a single piece of composite material. When using stitches, each row of stitches preferably
With 200 to 800 stitches, the row of stitches closest to the edge of the fabric is preferably at least four fibers away from that edge. For high float fabrics such as cotton sateen, where the high float is perpendicular to the connecting line, a spacing of at least 6 fibers is preferred. This means that for preferred types of fabric the edge overlap is at least 8 to
10 mm, preferably at least 16 or 20 mm. Of course, edges may be provided, but this increases the thickness of the fabric and is generally undesirable. To reduce the possibility of cutting the heat-recoverable fibers by the stitching (or stapling) operation, the needle (or staple) must be very sharp at its tip and cut between the heat-recoverable fibers of the fabric. It has a maximum diameter comparable to the distance. The advantages of stitching or stapling are: When a fiber contracts axially and recovers, its diameter or volume increases. As a result, the pores in the fabric through which the steps or staples are passing contract and the fabric grips the stitches or staples, thereby increasing the strength of the connection. Reducing the size of the pores helps any adhesive layer or matrix material to completely fill the pores, thus reducing the possibility of fluid leaking through the recovered article, which can e.g. It is particularly useful in articles used for environmental sealing in connection cases or corrosion protection of pipes or pipe insulation. Typically, composite structures are required to include a single piece of fabric embedded or bonded to a matrix polymer. However, in some cases, the composite structure may have multiple fabrics, e.g. two fabrics, with layers of polymer matrix between them, optionally with the matrix polymer facing outward. It may also be present on the surface. 1
Articles using fabrics exceeding 100% are particularly useful when surrounding substrates with high internal pressures, or when used in articles that are exposed to particularly severe mechanical attack. The invention will now be described in more detail with reference to the accompanying drawings. FIG. 1 is a perspective view of a wraparound article of the present invention (the thickness of the composite structure is exaggerated for clarity); FIG. 2 is a cross-sectional view of the article of FIG. , FIG. 3 shows the first layer after being wrapped around the base material.
FIGS. 4 and 5 are exploded cross-sectional views showing the end regions of the articles shown in FIGS. 4 and 5; FIGS. FIG. FIG. 1 shows a perspective view of an article of the invention, which is in the form of a wraparound device and is suitable for wrapping long substrates such as communications cable connections. Are suitable. The article is formed from a composite sheet 1 having heat-shrinkable filaments 3 in the warp direction and multifilament glass threads 4 in the weft direction. The fabric is completely embedded within the matrix polymer material 5, as shown more clearly in FIG. The matrix material 5 comprises two laminae 6 and 7 formed from a thermoplastic polymer, the laminae being laminated to opposite sides of the fabric, for example by a melt lamination process, and then cross-linked to each lamination 6. and 7 are glued to cloth and other flakes.
The flakes exhibit desired flow properties under selected recovery conditions. After the composite sheet is formed, a rail is formed along each of the ends extending along the weft direction and provides a means for holding the ends together after the article is wrapped around the substrate. supply Before or after forming the rails on the article, the composite sheet 1 is provided with a layer 10 of a sealant or adhesive, for example mastic or hot melt adhesive. This article has been found to have significant advantages over prior art articles. It has a very high ability to withstand hoop stresses caused e.g. by internal pressure, can be heat-shrinked by a torch with significantly lower chances of damage, is resistant to abrasion, and also has a very high tear resistance. . FIG. 3 is an enlarged exploded cross-sectional view showing the sealing rail of the article in position after the article has been wrapped around the substrate. Each rail is constructed by wrapping the excess portion of the composite sheet around a rod 12 formed from a high melting point material, such as nylon, and pressing surfaces 13, 14 or the excess portion together to form the rod 12 and the sheet. by forming a wall between other parts of the wall and then heating the remaining parts to fix them in the shape shown and cause partial recovery of the fibers in the wall. As shown, in one of the end portions:
The composite sheet is folded back on itself, while at the other end the sheet extends beyond the rail to form an underlying sealing flap. After the device has been wrapped around the substrate, the two end portions are brought together until they are engaged and a metal channel is fitted onto the rail, as shown for example in British Patent No. 1155470. to hold the end portions together and then the article is recovered. FIG. 4 shows a modification of the article shown in FIGS. 1-3 in which the composite sheet is folded along each end portion and provided with a separate polymeric sealing member 15 having a sealant layer 16. has been done. The sealing member may be formed from rubber or other elastomer, polyethylene, or the like. FIG. 5 shows still another improved example of the article, in which the sealing member 1
5 is joined to one of the end sections during manufacture. Next, examples will be shown to specifically explain the present invention. Example 1 Heat recoverable fabrics suitable for use in heat recoverable articles of the present invention were prepared by weaving high density polyethylene monofilament into fabrics in various weaves and then subjecting the fabrics to irradiation. . The fabric was irradiated with a 6 MeV electron beam in air at a dose rate of 0.24 Mrad/min. The properties of the fibers and fabrics are shown in Tables 1 and 2.

【table】

[Table] * Measured by refluxing in xylene.

【table】

[Table] Example 2 Twill fabric (60/1
0.23.6/3.9 cm) was extruded into a 0.5 mm thick sheet and laminated to a barely, if any, irradiated polymer matrix material to produce a heat recoverable composite sheet. Lamination was carried out by pressing between silicone rubber sheets under conditions appropriate to the polymer matrix material used. Lamination conditions are shown in Table 3.

[Table] Ethylene
The obtained composite structure was treated with a 6MeV electron beam,
Irradiation was allowed for a time sufficient to give a dose of 2.4 or 6 M rads for each sample at a dose rate of 0.24 M rads/min in air at room temperature. The properties of the polymer matrix materials are shown in Table 4. Table 5 also shows the recovery rate (%) of the composite structure.
In Table 5, the composite structures are from fabric N0.11 to
The composites were prepared by lamination with the polymer matrices shown in Table 4 and irradiation with an absorbed dose of 4M rad. The recovery rate of the composite structure is at least 40%, more preferably at least
65%, especially at least 70%.

【table】

[Table] Table 5 Composite Polymer matrix Recovery rate (%) 1 EVA 460 70 2 EVA 250 69 3 Linear low density polyethylene 68 4 DYNH-3 60 Example 3 High density cloth with a diameter of 0.29 mm as warp It was formed using polyethylene filament and 8-shaft satin using 75ECG glass fiber yarn as the weft. The density of the fabric (warp density/weft density) measured in fibers/inch or fibers/cm was 90/16 or 35.4/6.3. The fabric was irradiated with a 1.5 MeV electron beam at a dose of 15 Mrad to reach a gel content of 37.3% (refluxed with xylene) and 100% of the warp fibers.
The secant modulus was set to 0.60 (at 150°C). The fabric was then extrusion laminated with low density polyethylene at a melt temperature of 260° C. between cooled metal rolls and rubber faced rolls. The polyethylene has a thickness of 0.6mm on one side of the fabric and on the other side
It had a thickness of 0.3mm. After lamination, the composite is
Further irradiation was performed with a high-energy electron beam to a dose of 4M rad. The low density polyethylene used had a melt flow index of 3.0, a number average molecular weight of 14,800 and a weight average molecular weight of 114,800. After completion of the second electron beam irradiation, the low density polyethylene flakes constituting the matrix material had the following properties: 100% secant modulus at 60°C 4.8 MPa 100% secant modulus at 150°C 0.03 MPa Tensile strength at 150°C 0.13 MPa Elongation at break at 150°C 670% Gel content (refluxed with xylene) 39.2% Complex viscosity at 150°C and 1.0 RAD5 ^-1 2.79
×10 ⁵ poise High density polyethylene fibers irradiated with a dose of 20 Mrad have the following properties: 100% secant modulus at 150°C 0.29 MPa Tensile strength at 150°C 2.18 MPa At break at 150°C Elongation: 780% Gel content (refluxed in xylene): 42.25% Recovery force: 0.62 MPa Recovery rate: 87% Samples of the sheets thus formed were cut into dimensions of 15 inches (6 cm) in the warp direction and 30 inches (12 cm) in the weft direction. by wrapping the opposite ends parallel to the weft direction around a 3.5 mm diameter nylon rod, pressing the sealed area into the desired shape and heating to effect partial recovery of the fabric. A closure device as shown in FIG. 5 was then supplied. Before the closure device is formed,
0.4mm thick layer of polyamide adhesive (U.S. Patent No.
No. 4018733 or No. 4181775) was applied to the surface of a 0.6 mm polyethylene flake by a hot melt coating method. Wraparound articles produced in this manner have a recovery ratio of 4:1 (i.e. 75
%). This article was tested by creating a branch that split a 43 mm polyethylene jacketed communications cable into two 19 mm diameter polyethylene jacketed cables. Aluminum liner with foldable crown-like end (Raychem “XAGA”)
(registered trademark)) were arranged in a branched manner such that the central cylindrical part had a diameter of 92 mm. The article was then wrapped around the cable and liner and recovered onto them by heating with a propane torch. The article was sealed against leakage of pressurized gas between the article and the cable jacket in a known manner, and the crotches of the branches were sealed using clips as described in US Pat. No. 4,298,415. The cable was pressurized to an internal gauge pressure of 15 psi (1.05 Kg/cm ² ) and the branches were subjected to temperature cycling tests. In each cycle of the temperature cycle test, the temperature was raised from room temperature (23℃) to 60℃ over 1 hour.
The temperature was kept at 60°C for 4 hours, the temperature was lowered from 60°C to -30°C over 2 hours, and the temperature was kept at -30°C for 4 hours.
The temperature was then raised to room temperature (23°C) over 1 hour.
No leakage was recorded even after 10 cycles. Example 4 The fabric has a weft density of 18 threads/inch (7.1 threads/cm) and the recovery ratio of the composite fabric is 3.7:1 (or 73%)
Example 3 was repeated except that. Example 5 Example 3 except that the weft was changed from ECG75 glass fiber to ECG150 glass fiber, the fabric density was 90/18 (30.5/6.3 cm), and the recovery ratio in the warp direction was 4:1.
repeated. Example 6 Example 3 was repeated except that the glass fibers were replaced with multifilament yarns formed from aromatic polyamide filaments (commercially available from DuPont under the tradename "Kevlar"). This product had properties substantially similar to those of Example 3, but had a substantially higher trousers tear value (measured according to the British Standard) of 150N. Comparative Example 1 As a comparative example, a heat shrinkable fabric was made using a standard b-stage epoxy resin matrix polymer. The epoxy resin had the following composition: parts by weight of components Epoxy resin (Epoxy No. 475) (trade name
EPON1001, Ciel Chemical Co.) 70 Epoxy graft acrylic rubber modifier (Note 1) 30 Anchor 1699 (Product name) 9.8 Azelaic acid dihydrazidoimidazole (Accelerator) 1 Note 1: Acrylic elastomer (acid value 3000) (Product name "Vamac") (commercially available from DuPont) with bisphenol A epoxy resin (commercially available under the trade name "Epikote 1001") to have 11 epoxy groups per acid group. Each component was dissolved in methyl ethyl ketone to prepare a liquid with a solid content of 20%. Diameter 0.35 as warp
mm as unirradiated high density polyethylene and weft
60/12 (23.6/4.7cm) with ECG150 glass fiber
This solution was applied several times to a 2-up, 2-down twill fabric so that the resulting composite fabric had a thickness of about 0.75 mm. The composite fabric was then heated at 60°C for 1 hour,
B-staged epoxy resin. When the article thus formed is heated with a torch to recover, the viscosity of the matrix polymer decreases almost immediately to a value of about 50 poise, and then in a very short time the viscosity of the surface layer of the matrix decreases. A skin was formed on the matrix material that rose above 10 ⁸ poise, foamed, and inhibited fiber recovery to some extent. In addition, a large number of polyethylene fibers were cut during the recovery. Comparative Example 2 The fabric described in Comparative Example 1 was irradiated with a high-energy electron beam at a dose of 10 Mrad. When heated with a torch, the matrix material swells and
Cracks and numerous bubbles formed within the matrix material.
The maximum recovery ratio recorded was approximately 2:1 due to curing where the cured or partially cured matrix material holds the fibers against their recovery forces.

[Brief explanation of drawings]

1 is a perspective view of a wraparound article of the present invention; FIG. 2 is a cross-sectional view of the article of FIG. 1; and FIG. 3 is a view of the article shown in FIG. 1 after it has been wrapped around a substrate. An exploded cross-sectional view showing the end region of the article, and FIGS. 4 and 5 are exploded cross-sectional views showing the end region after the article shown in FIGS. 1-3 has been wrapped around a modified substrate. FIG. DESCRIPTION OF SYMBOLS 1... Composite sheet, 3... Heat-shrinkable filament, 4... Glass thread, 5... Matrix polymer material, 6, 7... Thin piece, 10... Adhesive layer, 1
2...Rod, 15...Sealing member, 16...Sealant layer.

Claims (1)

Claims: 1. A dimensional heat recoverable article having a composite structure comprising a heat recoverable fabric and a polymer matrix material, wherein: (a) the heat recovery fabric comprises fibers that recover when heated; (b) the polymer matrix material has a recovery stress (Y) of at least 5 x 10 ^-2 MPa at a temperature at or above the recovery temperature of the fiber; , the polymer matrix material has an elongation at break of greater than 20% and a 20% secant modulus (X) of at least 10 ^-2 MPa (measured at a tensile rate of 300%/min)
, and This is a related part. ] A heat-recoverable article characterized in that it has an elongation/temperature profile such that the temperature (T) at which T is less than 1 is at or above the recovery temperature of the fiber. 2. The article according to claim 1, wherein the heat-recoverable fiber has a recovery stress of at least 10 ^-1 MPa at a temperature equal to or higher than its recovery temperature. 3. The article according to claim 2, wherein the heat-recoverable fiber has a recovery stress of at least 5 x 10 ^-1 MPa at a temperature equal to or higher than its recovery temperature. 4. The article according to claim 3, wherein the heat-recoverable fiber has a recovery stress of at least 1 MPa at a temperature equal to or higher than its recovery temperature. 5. The article of claim 1, wherein the heat recoverable fibers are formed from a crosslinked polymeric material. 6. The article of claim 5, wherein the heat recoverable fibers are crosslinked to a gel content of at least 20%. 7. The article of claim 6, wherein the fibers have a gel content of at least 40%. 8. The article of claim 1, wherein the fabric comprises dimensionally thermostable fibers. 9. The article according to claim 8, wherein the heat-recoverable fibers are arranged in one direction, and the heat-stable fibers are arranged at an angle to the heat-recoverable fibers. 10. The article of claim 8 or 9, wherein the dimensionally thermostable fibers are glass fibers. 11. The article of claim 1, wherein the polymer matrix material has an elongation at break greater than 50% at or above the fiber recovery temperature. 12. The article of claim 11, wherein the polymer matrix material has an elongation at break of 100% or more at or above the fiber recovery temperature. 13. The article of claim 1, wherein the polymer matrix material is crosslinked. 14. The article of claim 1, wherein the polymeric matrix material has a complex dynamic modulus in the range of 10 ³ to 10 ⁸ cm ² . 15. The article of claim 1, wherein the matrix material surrounds at least a major portion of the surface area of the fibers making up the fabric. 16. The article of claim 15, wherein the fibers making up the fabric are completely enveloped by a matrix polymer material. 17. The article of claim 1, wherein the ratio of the volume occupied by the heat recoverable fibers to the total volume of the composite structure is at least 0.01:1. 18. The article of claim 17, wherein the ratio is in the range of 0.01:1 to 0.8:1. 19. The article according to claim 1, wherein X/Y (1-R)/R [wherein X, Y and R are as defined in claim 1] is less than 0.5. The article according to claim 19, wherein 20 X/Y (1-R)/R is less than 0.05. 21. The article of claim 1 having a layer of adhesive or sealant on at least a portion of the surface of the article. 22 Claim 21 having a layer of hot melt adhesive on at least a portion of the surface of the article
Items listed in section. 23. The article of claim 21 having a layer of mastic on at least a portion of the surface of the article. 24. The article of claim 1, wherein the structure comprises at least two heat recovery fabrics and a layer of polymeric matrix material interposed therebetween. 25. The article according to claim 1, wherein the structure has a tube shape. 26. The structure is open-shaped and has a pair of opposing end regions, and the article further includes a structure for retaining the end regions engaged during recovery of the article. An article according to claim 1, comprising a wrap-around rosier device. 27. The recoverable fibers are arranged substantially parallel to each other and the opposing end regions extend substantially perpendicular to the recoverable fibers.
Items listed in section. 28. An article according to any of claims 1 to 27, wherein the two or more parts of the composite structure are connected together using a mechanical connection device that passes through the fabric. 29. The article of claim 28, wherein the parts of the composite structure are connected together by one or more stitches. 30. The article of claim 28, wherein the parts of the composite structure are connected together with one or more staples. 31. An article according to any one of claims 28 to 30, wherein the composite structure has a hollow shape and is held in the hollow shape at least in part by the mechanical connection device. 32. The article of claim 31, wherein the hollow shape is generally tube-shaped. 33. Claim 3, wherein the hollow shape comprises at least two hollow regions communicating with each other.
Articles described in item 1. 34. The article of claim 33, wherein the hollow shape comprises at least two generally tubular regions. 35. Claim 31, wherein the hollow shape is a branched shape at the end of the generally tube-like region.
Items listed in section. 36. A method of making a dimensionally heat recoverable article having a composite structure rendered recoverable by a recoverable fiber component, the method comprising: (a) fibers that recover when heated; providing a heat-recoverable fabric, the fibers having a recovery stress (Y) of at least 5 x 10 ^-2 MPa at a temperature at or above the recovery temperature; (b) at or above the recovery temperature of the fibers; has an elongation at break of greater than 20% and a secant modulus (X) of at least 20% greater than 10 ^-2 MPa (measured at a tensile rate of 300%/min) at a temperature of )/R [R is the average effective volume fraction or related fraction of heat recoverable fibers in the composite structure along a given direction relative to the total volume of the composite structure. ] has an elongation/temperature profile such that the temperature (T) at which T is less than 1 is at or above the recovery temperature of the fiber. How to characterize it. 37. The method of claim 36, wherein the polymeric material is applied by hot lamination, spray coating or powder coating. 38. The method of claim 36 or 37, further comprising crosslinking the fibers of the fabric before applying the polymeric material. 39 Claim 3 in which the fibers are subjected to irradiation
The method described in Section 8. 40. The method of claim 39, wherein the irradiation is performed in the presence of oxygen. 41. The method according to any of claims 36 to 39, further comprising crosslinking the composite structure. 42. The method of claim 41, wherein the composite structure is subjected to irradiation.