Self-adhesive shaped body which is adapted to the anatomy, has a proprioceptive effect and is intended for medical purposes, having a bond strength of from 1 N/cm to 25 N/cm, an extensibility of more than 10%, a thickness of more than 0.5 mm and a resilience of more than 50% for a tensile stress of 5 N/cm2.

The invention relates to a self-adhesive shaped body, also referred to as a cushioning pad, and possessing high resilience, for orthopaedic purposes, especially for prophylaxis, postoperative treatment and therapy, especially for more rapidly reestablishing the function of injured joints, such as knee, ankle, shoulder, elbow and/or wrist joints.
The bandaging of joints, for example following injury or in the case of degenerative disorders, is a known method of orthopaedic treatment. The spectrum ranges from simple winding with more or less elastic bandages, through ready-made bandages in a wide variety of embodiments, and on to braces and splints of complex construction.
Additionally, the functional dressing technique, known as taping, is a treatment method for the prophylaxis and therapy of injuries, diseases and alterations on the locomotor apparatus. The purpose of taping is to mimic the capsular ligament structures and so achieve selective support and stabilization.
The actual tape dressing is applied in strips comprising preferably inelastic self-adhesive bands, known as straps, or in conjunction with self-adhesive bands having short-pull elasticity. It protects, supports and relieves vulnerable, damaged or disrupted parts of a functional unit. It permits selective loading within the pain-free sphere of movement, but prevents extreme or painful movements.
The application of such dressings, however, requires expert skill and experience and, consequently, cannot in general be performed by non-experts without taping experience.
A large number of bandages are known which aim to reestablish the function of injured joints.
EP 0 027 172 A1 describes a bandage in tube form for supporting and/or compressing knee, ankle, elbow and/or wrist joints. An adhesive coating of the bandage is not described.
An epicondylitis bandage is disclosed by EP 0 250 409 A1. An epicondylitis bandage of this kind consists essentially of a tube section comprising elastic material, the tensile stress in the peripheral direction being alterable by way of a tensioning strap which extends essentially in the peripheral direction and has a closure. The bandage is not self-adhesive.
DE 41 01 965 A1 discloses a joint bandage comprising elastic bandage material with a soft and a hard component and at least one friction core. Self-adhesive properties are not described. The joint bandage permits targeted transverse frictional massage for the more rapid reestablishment of the functions of injured joints such as knee, ankle, elbow, shoulder and wrist joints and has an insert which in the applied state acts on the joint and is designed as a compression cushioning pad, this pad having a form determined by the bone projections and tendon insertions of the joint and, as a shaped body, being formed from a soft or soft-elastic material in which at least one friction core comprising a hard or incompressible material is arranged and is fixed in its position in the material of the shaped body.
DE 42 37 389 A1 describes a knee joint bandage having corresponding anatomical forms. Self-adhesive properties are not described. The bandage for overcharge phenomena, femoropatellar pain syndromes and the patella tip syndrome, comprising an elastic bandage material in tube form with an encircling insert comprising a wavy knit, possesses, in the front part of the bandage, a cushioning pad which is situated in the region over the patella with the bandage applied, is upwardly open and leaves the quadricipital tendon free, and, in the rear part of the bandage, one or two cushioning pads which are arranged at a distance from one another and which act on the insert of the ischiocrural musculature.
It is an object of the invention to provide an anatomically designed shaped body for orthopaedic purposes which on the basis of the self-adhesive properties adheres to the skin or to an underlaid material, whereby owing to the high resilience of the shaped body when correctly applied a massage effect is established which leads to a more rapid reestablishment of the function of injured joints, such as knee, ankle, shoulder, elbow and/or wrist joints. In addition, the shaped body ought to improve the proprioceptive effect.
This object is achieved by means of a self-adhesive shaped body which is adapted to the anatomy and has a proprioceptive effect and is intended for medical purposes, as is described in the main claim. The subsidiary claims depict advantageous embodiments of the invention.
Accordingly, the invention provides a self-adhesive shaped body which is adapted to the anatomy, has a proprioceptive effect and is intended for medical purposes, having
a bond strength of from 1 N/cm to 25 N/cm,
an extensibility of more than 10%,
a thickness of more than 0.5 mm and
a resilience of more than 50% for a tensile stress of 5 N/cm2.
The shaped body of the invention is based on a composition which is designed so as to be self-adhesive by virtue of appropriate process steps or formulation with tackifiers.
To significant extents the body comprises an elastic polymer selected from the group consisting of polyurethane, polyester, polyether, polyepoxide, polyolefin and/or an elastic polymer based on a natural or synthetic rubber.
The technical properties of the shaped body may be adjusted depending on the field of use. In some cases, strongly adhering systems, or else less pressure-sensitive adhesive systems, are required for the shaped body. To this end, appropriate additives such as tackifier resins, plasticizers, stabilizers and other auxiliaries may be added to the respective system.
Advantageous embodiments exhibit a bond strength of from 1.5 to 22 N/cm, with particular preference from 1.5 to 18 N/cm. In one specific embodiment for the knee the bond strength is 14.5 N/cm. In another specific embodiment, for the elbow, the bond strength is 16.0 N/cm.
In one particularly preferred embodiment, the composition used to produce the shaped body is a thermoplastic hot-melt composition. The softening point of the thermoplastic hot-melt composition should be greater than 50xc2x0 C., since the application temperature in the course of production is generally at least 70xc2x0 C., preferably between 90xc2x0 C. and 190xc2x0 C. If desired, postcrosslinking by means of UV or electron beam irradiation may be appropriate. This depends on the chosen structure of the parent polymer or its additives.
The blending of block copolymers based on SEPS and SEBS for producing a shaped body of the invention, in particular, is notable for its diverse possibilities for variation. For particularly strongly adhering systems, the cohesive adhesive composition is based preferably on diblock (A-B) or triblock (A-B-A) block copolymers and/or mixtures thereof, preference being given to a diblock copolymer fraction of less than 80% by weight. The hard phase A is ideally polystyrene or its derivatives, and the soft phase B comprises ethylene and propylene and/or butylene or mixtures thereof.
The chain of the phase B may also include fractions of other kinds, such as, for example, isoprene, butadiene or similar substances. However, polystyrene blocks may also be present in the soft phase B, in proportions of up to 20% by weight. The overall styrene content, however, should always be lower than 65% by weight, preferably less than 40% by weight, with particular preference from 3 to 35% by weight. Preference is given to styrene fractions of between 3% by weight and 35% by weight, since a lower styrene fraction makes the adhesive composition more conforming.
In one advantageous embodiment the adhesive composition is composed as indicated below:
The aliphatic or aromatic oils, waxes and resins used as tackifiers are preferably hydrocarbon oils, waxes and resins, with the consistency of the oils, such as paraffinic hydrocarbon oils, or of the waxes, such as paraffinic hydrocarbon waxes, accounting for their favourable effect on the adhesion. Plasticizers used are medium- or long-chain fatty acids and/or their esters. These additions serve to establish the adhesion properties and the stability. If desired, further stabilizers and other auxiliaries are employed.
Filling the cohesive adhesive composition with mineral fillers, fibres, or hollow or solid microbeads is possible, so as to give, for example, a body of this kind comprising a hard core and a soft periphery. In use, this may give rise to a deep-down massage.
Advantageous for special applications are core materials having a Shore hardness (A) of less than 90, preferably from 80 to 10, with particular preference from 70 to 20. Rxc3x6mpp gives the following explanations in relation to the Shore hardness (Rxc3x6mpp Lexikon Chemiexe2x80x94Version 1.5, Stuttgart/New York: Georg Thieme Verlag 1998): According to DIN 53505 (1987-06), in the testing of elastomers and rubber, the Shore hardness corresponds to the resistance to penetration of a cone frustum (A or C) or of a rounded cone (D), as measured by the compression of a spring having defined spring characteristics and as expressed in dimensionless Shore A (C, D) hardness units. In the case of the testing of steel, the Shore rebound hardness is measured in the so-called scleroscope, in which the rebound height of a hammer which falls on the test surface in a vertical tube is measured.
In other embodiments, this core material is not adhesive.
For specific application, furthermore, natural rubber or other synthetic rubber types, such as butyl rubber, chloroprene and silicone rubber, may be used.
For stressed joint regions in particular, stringent requirements are imposed in respect of the adhesion properties. For ideal application, the shaped body should possess a high tack. Furthermore, so that there is no slipping, the pressure-sensitive adhesive composition chosen for producing the shaped body is required to possess high shear strength. The targeted reduction in the glass transition temperature of the pressure-sensitive adhesive composition, as a consequence of the selection of the tackifiers, of the plasticizers and of the polymer molecule size, and of the molecular distribution of the components employed, achieves the necessary bonding, appropriate to its function, with the skin, even at critical points on the human locomotor system, and/or with an underlaid material. Product properties such as tack and shear stability may be quantified readily with the aid of a dynamomechanical frequency measurement. In this case, use is made of a rheometer controlled by shearing stress. The results of this measurement method give information on the physical properties of a substance by taking into account the viscoelastic component. In this instance, at a predetermined temperature, the cohesive adhesive composition is set in oscillation between two plane-parallel plates with variable frequencies and low deformation (linear viscoelastic region). Via a pickup control unit, with computer assistance, the quotient (Q =tan xcex4) between the loss modulus (Gxe2x80x3, viscous component) and the storage modulus (Gxe2x80x2, elastic component) is determined.
Q=tan xcex4=Gxe2x80x3/Gxe2x80x2
A high frequency is chosen for the subjective sensing of the tack and a low frequency for the shear strength. A low numerical value denotes low tack and good shear stability.
In accordance with the invention, to form the shaped body, preference is given to pressure-sensitive adhesive compositions in which the ratio of the viscous component to the elastic component at a frequency of 100 rad/s at 25xc2x0 C. is greater than 0.4, or to adhesive compositions where the ratio of the viscous component to the elastic component at a frequency of 0.1 rad/s at 25xc2x0 C. is less than 0.5, preferably between 0.35 and 0.02, with very particular preference between 0.3 and 0.05. The adhesive compositions are also preferably formulated so that at a frequency of 0.1 rad/s they have a dynamic-complex glass transition temperature of less than 25xc2x0C., preferably of less than 10xc2x0C., with very particular preference from 5xc2x0 C. to xe2x88x92150xc2x0C.
Because of the ratio, chosen ideally in accordance with the invention, the cushioning pads exhibit favourable resilience properties. In one preferred embodiment, with a tensile stress of 5 N/cm, based on the width of the article, a resilience of more than 50%, preferably from 55% to 98%, with particular advantage from 60% to 90%, is obtained. In this way, fatigue of the material, as occurs for example under the load conditions of a sport, is reduced. The high shear strength of the adhesive composition is achieved by means of the cohesive nature of the polymer, especially block copolymer.
A further-reaching improvement in relation to the known prior art can be achieved by providing extensible embodiments of the cushioning pads. In this case, an improvement in the proprioceptive effect is found for long-term application, since cushioning pads of inadequate extensibility do not bond durably and thus have a much-reduced, or absent, proprioceptive effect. The extensibility depends on the corresponding use of the product. In general, extensions of more than 10% are necessary. For one specific embodiment on the knee, the minimum extensibility should be 70%; for another specific embodiment for use on the elbow, it should be 50%.
In one particular embodiment, the shaped body may be dehered by extension; for this purpose, as well, good extensibility of the cushioning pad material is required.
Another particular embodiment of the shaped bodies is doped with releasable substances having a local or systemic action. In one specific case, the shaped body which can be dehered by extension has been treated with an active substance which can be released to the skin.
The shaped bodies may be produced from the melt of the abovementioned composition. A variety of production processes may be suitable in this case, whereby advantages may arise depending on the intended use. Common modes of production are casting, compression moulding, injection moulding, spraying, extrusion, calendering and also punching, embossing, stretching, cutting or a combination thereof.


An improved tube inspection probe delivery system that supports a probe pusher that drives a cable connected to the probe through a flexible conduit into a tube for inspection. The probe pusher is mounted on an elevator that advances the probe pusher toward or retracts the probe pusher from the general direction of the tube as the probe is moved from tube to tube for inspection of a plurality of tubes, to maintain a substantially constant slack in the flexible conduit. The probe drive system includes a containment to control contamination that may be emitted from the tube during the inspection process.

Pressurized water nuclear reactors employ steam generators to isolate and place a radioactive coolant, flowing in the primary circulation loop, in heat exchange relationship with a secondary fluid from which steam is generated to circulate in a secondary circulation loop. The steam generally is employed to drive a turbine to perform work, e.g., motor an electric generator. In the primary loop the reactor coolant is heated by the nuclear reactions occurring in the reactor core and circulated through a hot piping leg to a hemispherical bowl shaped portion of the primary side of the steam generator generally known as the channel head. The channel head is separated, by a partition across its diameter, into inlet and outlet plenims, which are covered by a tube sheet through which the terminating ends of U-shaped heat exchanger tubes are fastened. Each of the U-shaped heat exchanger tubes originate in a bore in the tube sheet passing from the inlet plenim of the channel head and terminate in a bore in the tube sheet that communicates with the outlet plenim of the channel head. A cylindrically shaped secondary side of the steam generator is disposed around and over the tube sheet and the U-shaped heat transfer tubes. Hot, radioactive water from the reactor core circulates through the primary side of the steam generator, while non-radioactive water is introduced into the secondary side. The tube sheet and heat exchanger tubes hydraulically isolate but thermally connect the primary side to the secondary side. Hot radioactive water from the primary side flows through the interior of these heat exchanger tubes while the exterior of these tubes come into contact with the non-radioactive water in the secondary side in order to generate non-radioactive steam.
In the secondary side of the steam generator exterior portions of the U-shaped heat exchanger tubes are supported by and extend through bores present in a plurality of horizontally supported plates that are vertically spaced along the elongated length of the tubes. Small annual spaces are present between the heat exchanger tubes and the bores in the support plates, and the tube sheet, which are known in the art as xe2x80x9ccrevice regions.xe2x80x9d Such crevice regions provide only a very limited flow path for the feed water that circulates throughout the secondary side of the steam generator, which causes xe2x80x9cdry boilingxe2x80x9d to occur wherein the feed water boils so rapidly that these regions can actually dry out during operation of the steam generator. This chronic drying out causes impurities in the water to precipitate and collect in these crevice regions. These precipitates ultimately create sludge and other debris that promotes the occurrence of corrosion in the crevice regions which, if not repaired, can ultimately cause the tube to crack and to allow radioactive water from the primary side to contaminate the non-radioactive water in the secondary side of the steam generator.
Eddy current probe systems are employed to monitor the extent of degradation in the walls of the heat exchanger tubes that result from corrosion. One such system is described in U.S. Pat. No. 5,174,165 issued Dec. 29, 1992 to the assignee hereof. One of the services performed at a nuclear power plant is eddy current inspection of the steam generator tubing using such a system. The inspection involves insertion and removal of various configurations of eddy current probes in the high radiation and contaminated area of a nuclear steam generator. Minimizing personal time and equipment near the manway opening through which access to the interior of the steam generator is obtained (generally referred to as the steam generator platform) is highly desirable due to the elevated radiation level in that area. Typically the probes are attached to a long flexible piece of tubing (poly) and driven with a probe pusher through a flexible conduit to an area of interest or the entire length of the steam generated tube. One end of the flexible conduit is generally fixed to the probe pusher while the opposite end is attached to and positioned under the steam generator tube with a robotic manipulator. Usually two probe pushers are used, side by side, so that two tubes can be inspected simultaneously.
Pushing the probe into the tube can be difficult due to many factors including steam generator U-bends, the length of poly, bends in the conduit, the overall length of the conduit used, moisture and restrictions in the steam generator tube. For these reasons, the probe pushers are usually located on the steam generator platform or mounted directly on the steam generator to minimize the length of flexible conduit through which the probe has to be pushed. Therefore, the probe operators are exposed to a high radiation area and the probe pusher equipment cannot be set up until the steam generator manways are removed or they would be in the way of that operation.
A second problem during eddy current inspection is that the amount of conduit in the steam generator needs to be increased or decreased as the robotic manipulator moves to various tube locations. This task is typically accomplished by manually adding or removing sections of the flexible conduit on the steam generator platform, which is a source of radiation exposure time for the field service operators.
A third area of concern is the containment of radioactive particles that are carried from the steam generator tubing by the eddy current probe and poly. Typically, eddy current testing is a major contributor of radioactive contamination on the steam generator platform, which increases down time for decontamination, monitoring, and field service personnel change out due to personnel contamination. Localized vacuum systems located near the probe pusher wheels or poly are utilized to capture radioactive particles but there is still spread of radioactive particles due to the ineffectiveness of the vacuum systems and the physical handling of probes and polys during replacement.
A final problem is that, quite frequently, the probe must be passed through calibration standards during an eddy current inspection program. If the standards are fastened to the manway, the robot must flip the conduit upside down making it difficult to remotely pass the probe through the standard. If the standards are placed in line with the conduit they make the probe pushing difficult due to management of the long standard in the steam generator.
To further improve the inspection process it would be desirable to locate the probe pushers remote from the steam generator without compromising the push capability. This would reduce personnel exposure by enabling field service personnel to operate and service the pushers and probes in a lower radiation exposure area. It would also remove the current equipment from the steam generator platform and provide additional space for other activities in a normally congested work area. Furthermore, it would enable the equipment to be set up and functionally tested prior to removal of the steam generator manways providing a direct time savings for the field crew and in some situations plant critical path.
It is an object of this invention to overcome these difficulties.
These and other objects are achieved by a system and method which enables the eddy current probe drive system to be located below the steam generator platform without impeding the push capability of the probe pushers. This is accomplished by mounting the probe pushers on an elevator that can raise and lower the conduit toward or from the tube sheet to maintain the slack in the conduit substantially the same for all positions of the robotic arm under the tube sheet. This minimizes the number of bends in the conduit which can cause an obstruction to the movement of the probe and maximizes a straight section between the manway and the probe pusher in which the calibration standard can be incorporated.
In the preferred embodiment a tent is slipped over the probe pusher having an open end through which the conduit passes and a vacuum port at a spaced distance from the open end, with the end of the tent opposite the open end closed. A vacuum drawn through the port draws air into the tent and funnels substantially all the contamination out the vacuum port from which it can be collected. Preferably, the tent is provided with a number of access doors through which the probe pusher, conduit and probe can be accessed for maintenance.
Preferably, retractable legs are provided that can stabally support the system during operation and retract for transport and storage to reduce the overall size of the system. Desirably, the legs are provided with height adjustments that can change the angular orientation of the probe pushers relative to the tube sheet.

Tube non-destructive testing probe drive elevator and contamination containment system


A non-reusable needle-bearing safety medical device is provided. The device is operable for inserting an intravenous catheter into a patient. The device includes a needle for piercing the patient""s skin and guiding the catheter into the vein of the patient. The needle is operable in two positions, an extended position, in which the needle projects forwardly from a housing, and a retracted position, in which the needle is retracted into the barrel so that the needle is enclosed by the barrel to prevent inadvertent contact with the needle after use. A needle retainer releasably retains the needle in the projecting position against the bias of a spring that biases the needle rearwardly toward the retracted position. After use, the operator displaces an actuator to release the needle. The spring then propels the needle rearwardly into the retracted position. In this way, the device is non-reusable and the needle is shielded to prevent contact with the sharpened tip of the contaminated needle.

The present invention relates to needle-bearing medical devices used, for example, to insert catheters or guide wires into blood vessels of patients or to sample fluid from patients. More specifically, the invention relates to such a device having a retractable needle feature for rendering the device non-reusable and safely disposable.
Various types of medical devices employ a needle for piercing the skin of a patient for diagnostic or therapeutic purposes. One such device is an intravenous catheter insertion device, wherein a needle-mounted catheter is positioned within a patient""s vein. Once the catheter is properly positioned, the catheter insertion device is withdrawn leaving the catheter in place. Handling of such needle-bearing medical devices after the needle is withdrawn from the patient can result in transmission of various pathogens, most notably human immune virus (HIV), to uninfected medical personnel, due to an inadvertent needle prick.
Since the mid-1980s, concern over the risk of accidental needle stick injuries has spawned a number of design approaches for safety needle devices. Such devices can be broadly categorized as sliding sheath needle devices, wherein a physical barrier is positioned about the needle tip after use, and as needle-retraction devices, wherein the tip of the needle is retracted into the device after use. The category of needle retraction devices can be further subdivided into manual and automatic retraction devices. Manual retraction devices, as exemplified by U.S. Pat. Nos. 4,026,287 to Haller, U.S. Pat. No. 4,592,744 to Jagger, U.S. Pat. No. 4,808,169 to Haber et al. and U.S. Pat. No. 5,067,490 to Haber, require the user to pull or slide a needle-engaging mechanism rearwardly for a sufficient distance to retract the needle into the device. In automatic needle retraction devices, a biasing member, such as a spring, is employed to push or pull the needle into the device in response to activation of some release mechanism by the user. Such devices are exemplified by U.S. Pat. No. 4,813,426 to Haber et al. and U.S. Pat. No. 5,125,414 to Dysarz.
U.S. Pat. No. 4,747,831 assigned to Becton Dickinson and U.S. Pat. No. 4,900,307 to Kulli show respective automatic retractable-needle catheter stylets and syringes. The devices shown in the last-mentioned two patents are disclosed to be actuatable by the user who applies a simple unitary motion that entails a simple single-stage actuation movement in just one direction. Specifically, these latter patents show devices in which retraction is effected by depressing a single surface or member for a short distance in a single direction. Hence, during use of such devices, the user must be mindful not to prematurely trigger the needle retraction mechanism by accidentally contacting the surface for actuating the retraction mechanism. Since medical needle bearing devices are frequently employed under distracting circumstances, it would be desirable to provide an automatic needle retraction mechanism in which a compound action or dual motion is required by the user in order to effect automatic retraction of the needle. Such a mechanism would desirably require the user to act upon more than one surface of the retraction mechanism to effect withdrawal of the needle into the device. It further would be desirable to require that such actions to retract the needle occur along different directional axes to further decrease the likelihood of undesired premature or accidental retraction of the needle.
Of the aforementioned prior art devices which have automatic needle retraction mechanisms, all require a needle structure having an enlarged head, lip or rim extending radially outwardly from the axis of the needle to provide a block or enlarged surface on the needle which is biased toward retraction by the spring and which can be restrained against retraction by a latching arrangement or latch mechanism. In such devices, failure of the latch mechanism can occur to cause premature retraction of the needle. Hence, it would be desirable to provide an automatic needle retraction mechanism in which the latch mechanism operates more directly upon the needle.
After use of a needle bearing medical device, a small volume of contaminated fluid or blood may remain inside the needle after it is withdrawn from the patient. Depending upon the gauge of the needle used with the device, such residual fluid or blood may be ejected from the forward end of the needle during the rearward acceleration experienced in retraction of the needle. Such forward fluid ejection can result from insufficient capillary adhesion to retain the residual fluid against inertial forces during needle retraction, or against the hydraulic force exerted upon the residual fluid by inrushing fluid or air during rearward acceleration in retracting the needle. It would also be desirable to provide a structure in an automatic needle retraction device that would prevent such ejection of residual blood or fluid from the forward end of the needle during retraction.
In accordance with one aspect of the present invention, there is provided a needle retraction mechanism for a needle bearing medical device wherein a needle retaining member is bonded directly to the needle for selectively holding the needle in a projecting configuration from the device. The needle retaining member has an axial extension configured to provide at least one finger, and preferably a plurality of separable fingers that are joined about a central bore for holding the needle axially within the bore. Mutual engagement between the fingers and the needle can be enhanced by adhesive or thermal bonding. The needle retainer is positioned within the device to restrain the needle against rearward bias exerted upon the needle by a spring. The spring is preferably also bonded directly to the needle, so that neither the bias force or the counteracting restraining force is required to be mediated by any additional structure connected to the needle.
In accordance with another aspect of the present invention, the needle bearing medical device is provided with an automatic retraction mechanism in which the user is required to execute a dual or compound motion in order to actuate the needle for withdrawing the needle into the device by movement of a biasing member. The preferred compound motion requires the user to effect two motions on separate surfaces of the device. Furthermore, these motions are preferably designed to be effected in distinct directions in order to assure intentional needle retraction.
In accordance with another aspect of the present invention, a dual-motion needle retraction mechanism is provided in combination with respective catheter insertion and guide wire insertion devices.

Catheter insertion device with retractable needle


The invention relates to a composite material which has at least one formation comprising fibers and aerogel particles and is characterised in that the fibrous formation contains at least one thermoplastic fibrous material to which the aerogel particles are bound and by which the fibers in the formation are bound together. It also relates to a process for the production of said composite material, and the use thereof.

The present invention relates to a composite material that contains at least one formation of fibrous material and aerogel particles, a process for the production of this, and the use thereof.
Because of their very low density, high porosity, and small pore diameters, aerogels, in particular those with porosities of greater than 60% and densities of less than 0.4 g/cm3, exhibit very low thermal conductivity and for this reason are used as thermal insulating materials as is described, for example, in EP-A-O 171 722.
However, their great porosity results in very poor mechanical stability, both of the gel from which the aerogel is dried, as well as of the dried aerogel itself.
In the broadest sense, i.e., when regarded as xe2x80x9cgels with air an the dispersed material,xe2x80x9d aerogels are manufactured by curing a suitable gel. When used in this sense, the term xe2x80x9caerogelxe2x80x9d includes aerogels in the narrower sense, such as xerogels and cryogels. A gel is designated as an aerogel in the narrower sense if the liquid is removed from the gel at temperatures above the critical temperature and starting from pressures that are above the critical pressure. In contrast to this, if the liquid is removed from the gel sub-critically, for example with the formation of a liquid-vapour boundary phase, then the resulting gel is, in many instances, referred to as xerogel. It should be noted that the gels according to the present invention are aerogels in the sense that they are gels with air as the dispersed material.
The process that shapes the aerogel in concluded during the sol-gel transition. Once the solid gel structure has been formed, the external shape can only be changed by size reduction, for example, by pulverizing. The material is too brittle for any other form of processing.
For many applications, however, it is necessary to use the aerogel in certain shapes. In principle, the production of shaped parts is possible even at the gel is being formed. However, the replacement of solvents, typically required during production, and which is governed by diffusion (with respect to aerogels, see, for example, U.S. Pat. No. 4 610,863 and EP-A 0 396 076; with respect to aerogel composite materials, sea, for example, WO 93/06044), and the dryingxe2x80x94which is similarly governed by diffusionxe2x80x94lead to production times that are economically unacceptable. For this reason, it is appropriate to carry out a shaping stage after the production of the aerogel, which is to say, after it has been dried, and to do this without any essential change of the internal structure of the aerogel taking place with respect to the particular application.
For many applications, e.g., in order to insulate curved or irregularly shaped surfaces, it is necessary to use flexible panels or mats of insulating material.
DE-A 33 46 180 describes rigid panels from shaped bodies based on silicic acid aerogel obtained by flame pyrolysis combined with reinforcement by long mineral fibres. However, this silicic acid aerogel that is extracted from flame pyrolysis is not an aerogel in the above sense since it is not manufactured by curing a gel, and for this reason it has a completely different pore structure. Mechanically, it is much more stable and for this reason can be pressed without destruction of the microstructure, although it has a greater thermal conductivity than typical aerogels in the above sense. The surface of a moulded body such as this is extremely delicate and for this reason must be hardened, as by the use of a binder, or by being covered with a film. Furthermore, the resulting shaped body cannot be compressed.
DE-A-44 18 843 describes a mat of a fibre-reinforced aerogel. It is true that, because of the very high proportion of aerogel, these mats display a very low level of thermal conductivity, but they require relatively protracted production times because of the above-described diffusion problems. In particular, it is only possible to manufacture thicker mats by combining a number of thinner mats, and this involves additional outlays.
It is the task of the present invention to produce a composite material that is based on aerogel granulate, that has a lower level of thermal conductivity, and is both mechanically stable and easy to manufacture in the form of mats or panels.
This problem has been solved by a composite material that contains at least one formation of fibrous materials and aerogel particles, which is characterised in that the fibrous formation contains at least one thermoplastic fibrous material with which the aerogel particles are connected and by which the fibres are connected to each other in the formation in such a way that the thermoplastic fibres at the surface are fused and on cooling result in a joining of the fibres to each other and to the aerogel particles. This thermal consolidation ensures a stable fibrous formation and ensures that the aerogel particles are bonded to the fibres.
Here, a fibrous formation in understood to be any formation that can be produced using a surface-forming technique. Examples of such surface formations are textile fabric, random-fibre matting, knitted fabrics, and fleeces, with fleeces being preferred.
Fleeces understood to include the so-called stable fibre mats, i.e., random-fibre mats of fibres that are of finite length, as well as spun-fibre mats, i.e., those that are of continuous fibres.
In the case of thermoplastic fibres, hereinafter referred to as the first fibre material, these can be fibres of a thermoplastic, organic material such as, for example, polyolefin fibres, polyamide fibres, or preferably polyester fibres. The fibres can be round, trilobal, pentalobal, octalobal, in the form of strips, or be shaped like fir trees, dumb bells, or otherwise. Hollow fibres can also be used. The first fibre materials can be a smooth or crimped.
In addition, the fibrous formation can contain at least one extra fibre material that is bonded to the first fibres of thermoplastic material during the thermal consolidation process. To this end, the melting point of the material from which these fibres are made may not be lower than the temperature at which the fleece becomes thermally consolidated. In the case of the fibres, these can be both inorganic fibres, such as mineral or glass fibres, or organic fibres, such as polyolefin, polyamide, or polyester fibres or mixtures thereof. It is preferred that the additional fibres be of the identical material as the first fibres, although of another profile, another diameter, or display another type of crimping and/or another degree of elongation.
The fibres can be modified by conventional additives, for example anti-static agents such as carbon black. The fibres that are contained in the formation can contain IR opacifiers, such an carbon black, titanium dioxide, iron oxide, or zirconium dioxide, as well as mixtures of these, in order to reduce the radiation contribution to thermal conductivity. The fibres may also be dyed in order that they are coloured.
The diameter of the fibres that are used in the composite material should preferably be smaller than the mean diameter of the aerogel particles, so that a high proportion of aerogel can be bound into the composite material. The selection of very fine fibres makes it possible to produce mats that are very flexible, whereas the use of thicker fibres results in bulkier mats that are stiffer on account of their greater resistance to bending.
The denier of the fibres is preferably between 0.8 and 40 dtex.
Mixtures of fibres that are of different materials, with different profiles and/or different deniers can also be used. Mixing in thicker fibres results in greater resistance to bending. In order to achieve good consolidation of the fleece, on the one hand, and to ensure good adhesion of the aerogel granulate on the other hand, the proportion by weight of the first, thermoplastic fibrous material should be between 10 and 100%-wt, preferably between 40 and 100%-wt, relative to the total quantity of fibre.
Of the spun fleeces, those that are of fibres of synthetic polymers, the so called spun bonds, are preferred; these are produced from random-laid freshly melt-spun filaments. They consist of continuous synthetic fibres that are of polymer materials that can be melt-spun. Suitable polymer materials are, for example, polyamides such as polyhexamethylene diadipamide, polycaprolactam, aromatic or partially aromatic polyamides (aramids), aliphatic polyamides such as nylon, partially aromatic or fully aromatic polyesters, polyphenylsulfide (PPS), polymers with ether or keto groups, such as polyetherketones (PEK) and polyetherether ketone(PEEK),or polybenzimidazoles.
It is preferred that the spun mats consist of melt-spinnable polyesters. In principle, all known polyester materials that are suitable for the production of fibres can be used. Polyesters of this kind consist mainly of building blocks that are derived from aromatic dicarboxylic acids and from aliphatic diols. Common aromatic dicarboxylic acid building blocks are the divalent radicals of bensenedicarboxylic acids, in particular of terephthalic acid and isophthalic acid. Common diols have 2 to 4 carbon atoms, ethylene glycol being particularly suitable. Particularly advantageous are spun fleeces that consist of at least 85 mol-% polyethyleneterephthalate. The remaining 15 mol-% is then built up from dicarboxyltc acid units and glycol units that act as so-called modifying agents and which permit the practitioner skilled in the art to alter the physical and chemical properties of the filaments that are produced. Examples of such dicarboxylic acid units are radicals of isophthalic acid or of aliphatic dicarboxylic acids such as, for example, glutaric acid, adipic acid, sebacic acid; examples of modifying diol radicals are ones of the long-chain diols such as propanediols or butanediol, of di- or triethylaneglycol or, to the extent that they are present in small quantities, of polyglycol with a molar weight of approximately 500 to 2000. Particularly preferred are polyesters that contain at least 95 mol-% polyethyleneterephalate (PET), in particular those of unmodified PET.
If the composite materials according to the present invention are also to have a flame-retardant effect, it is an advantage if they have been spun from flame-retardant modified polyesters. Such flame-retardant modified polyesters are known. They contain additives of halogen compounds, in particular bromine compounds or, what is particularly advantageous, they contain phosphonic compounds that are condensed into the polyester chain.
It is particularly preferred that the spun mat contain flame-retardant modified polyesters that are condensed into the chain component group of formula (I)
wherein R stands for alkylene or polymethylene with 2 to 6 carbon atoms or phenyl, and R1 stands for alkyl with 1 to 6 carbon atoms, aryl, or aralkyl, these being condensed in. It in preferred that in Formula (1) R stands for ethylene and R1 stands for methyl, ethyl, phenyl, or o-, m-, or p-methyl-phenyl, in particular methyl. Spun mats of this kind are described, for example, in DE-A-39 40 713.
It is advantageous that the polyesters contained in the spun fleeces have a molecular weight corresponding to an intrinsic viscosity (IV) of 0.6 to 1.4 as measured in a solution of 1 g polymer in 100 ml dichloracetic acid at 25xc2x0 C.
The individual denier of the polyester filaments in the spun mats is between 1 and 16 dtex, preferably 2 to 8 dtex.
In another embodiment of the present invention, the spun fleece can also contain another fibre material as carrier fibres. Spun fleeces of this kind are described in EP-A-0,446,822, EP-A-0,530,769, and EP-A-0,590,629.
Examples of polymers from which the carrier fibres can be derived are polyacrylonitrile, polyolefins such as polyethylene, essentially aliphatic polyamides such an nylon 6.6, essentially aromatic polyamides (aramids), such as poly-(p-phenylene terephthalate) or copolymers containing a proportion of aromatic m-diamine units to inprove solubility, or poly-(m-phenylene isophthalate), essentially aromatic polyesters such as poly-(p-hydroxybenzoate) or preferably essentially aliphatic polyesters such as polyethylene terephthalate.
The proportion of the two types of fibres relative to each other can be selected within a very wide range. although attention must be paid to the fact that the proportion of the thermoplastic fibres must be sufficiently great that the adhesion of the carrier fibres to the thermoplastic fibres makes the fleece material strong enough for the intended application. Then, the proportion of thermoplastic fibres usually amounts to less than 50%-wt relative to the weight of the mat material.
Suitable thermoplastic fibres are, in particular, modified polyesters with a melting point that is 10 to 50xc2x0 C., and preferably 30 to 50xc2x0 C. lower than that of the raw material used for the fleece material. Examples of ouch fibre materials are polypropylene, polybutylene terephthalate, or polyethylene terephthalate modified by condensing in longer-chain diols and/or isophthalic acid or aliphatic dicarboxylic acid.
The carrier fibres and the thermoplastic fibres are preferably built up from one class of polymer. It is to be understood that all the fibres that are used have been no selected from a class of substances that once the fleece reaches the end of its useful life, it can be recycled without any problem.
The individual fibre denier of the carrier fibres and of the thermoplastic fibres can be selected within very wide limits. Examples for such denier ranges are 1 to 16 dtex, preferably 2 to 6 dtex.
In one other embodiment, the spun fleece can be finally consolidated after mechanical consolidation by needling and/or by means of fluid jets, optionally with the help of a chemical binder, for example, one that is based on a polyacrylate.
The weight to area ratio of the spun fleece is between 20 and 500 g/cm2, and between 30 and 250 g/m2.
The volumetric percentage of the aerogel within the composite material should be as high as possible, and should amount to at least 40%, and should preferably be above 60%. In order to achieve mechanical stability of the composite material, the percentage should not, however, exceed 95%, and should preferably not be above 90%.
Aerogels that are suitable for the compounds according to the present invention are those that are based on metal oxides that are suitable for the sol-gel technique (C. J. Brinker, G. W. Scherer, Sol-Gel Science. 1990, Chaps. 2 and 3), for example, Si or Al compounds, or those based on organic substances that are suitable for the sol-gel technique, ouch as melamine-foraldehyde condensates (U.S. Pat. No. 5,086,085) or resorcinol-formaldehyde condensates (U.S. Pat. No. 4,873,218). They can also be based on mixtures of the above-cited materials. It is preferred that aerogels containing Si compounds, especially SiO2 aerogels, and in particular SiO2 aerogels, be used. The aerogel can contain IR opacifiers, such as carbon black, titanium dioxide, iron oxide, or zirconium dioxide, as well as mixtures of these, in order to reduce the radiation contribution to thermal conductivity.
Furthermore, the thermal conductivity of the aerogels decreases as porosity increases and density decreases. For this reason, aerogels with porosities of greater than 60% and densities of less than 0.4 g/cm3 are especially preferred.
The thermal conductivity of the aerogel granulate should be less than 40 mW/mK, and in particular less than 25 mW/mK.
In one preferred embodiment, the aerogel particles have hydrophobic surface groups. In order to avoid any subsequent collapse of the aerogels by the condensation of moisture within the pores, it is advantageous if hydrophobic groups which are not split off when acted upon by water be present covalently on the inside surface of the aerogel. Preferred groups for the permanent hydrophobisation are trisubstituted silyl groups of the general formula xe2x80x94Si(R)3, with trialkyls and/or triarylsilyl groups being preferred, with each R independently being a non-reactive, organic radical such as C1-C18-alkyl or C6-C14-aryl, preferably C1-C6 alkyl or phenyl, in particular methyl, ethyl, cyclohexyl, or phenyl, which can be additionally substituted with more functional groups. Particularly advantageous for permanent hydrophobisation of the aerogel is the use of trimethylsilyl groups. The incorporation of these groups can be effected as has been described in WO 94/25149, or it can be done by gas-phase reaction between the aerogel and an activated trialkylsilane derivative, such as chlortrialkysilane or a hexaalkylsilazane, for example (Cf. R. Iler, The Chemistry of Silica, Wiley and Sons, 1979).
The size of the grains will depend on the use to which the material is put. However, in order to be able to bind in a large percentage of aerogel granulate, the particles should be greater than the diameter of the fibres, preferably greater than 30 xcexcm. In order to achieve a high level of stability, the granulate should not be too coarse, and the grains should preferably be smaller than 2 cm.
Granulate with a favourable bimodal grain size distribution can be used to achieve a high volumetric percentage of aerogel. Other distributions could also be used.
The fire rating of the composite material is determined by the fire rating of the aerogel and of the fibres. In order to arrive at the most favourable fire rating for the composite material, non-flammable fibres such as glass or mineral fibres, or fibres that are difficult to ignite, such as TREVIRA CS(copyright), should be used.
If the composite material consists only of the fibrous formation that contains the aerogel particles, the aerogel granulate may break when the composite material is subjected to mechanical loads, or can break away from the fibres so that the fragments can fall out of the formation.
For this reason, for specific applications, it is advantageous that the fibre fleece be covered on one or both sides with, in each instance, at least one covering layer, which covering layers can be identical or different. As an example, the covering layers can be cemented over the thermoplastic fibres by means of another adhesive during thermal consolidation, the covering layer being, for example, preferably a metal foil or a metallised plastic film. In addition, the particular covering layer can itself consist of a plurality of layers.
What is preferred in a fibre-aerogel composite material in the form of mats or panel, which has a fibrous formation that contains an aerogel as the middle layer and on each aide has a covering layer, at least one of these covering layers containing layers of fine thermoplastic fibres, with the individual fibre layers being thermally consolidated in and of themselves and to each other. The covering layer can also contained bi-component fibres. Bi-component fibres are chemical fibres of two rigidly connected polymers that are of different chemical and or physical structure, which have areas with different melting points, i.e., areas of a low melting point and areas of a higher melting point. Typically, these fibres are in the form of a core-and-covering structure in which the low melting point components form the covering, or else they are of a side-by-side structure.
The choice of the fibres for the covering layer is governed by the same factors as those that govern the choice of fibres for the fibre formation in which the aerogel particles are bonded in. In order to obtain the densest possible covering layer, however, the fibres should be of a diameter smaller than 30 xcexcm, and preferably smaller than 15 xcexcm.
In order to arrive at the greatest stability or density of the surface layers, the layers in the covering layer can be needled.
A further object of the present invention is to describe a process for manufacturing the composite material according to the present invention.
Production of the composite material according to the present invention is described in detail below with respect to the preferred fibre mat, although it is not restricted to this period Yorker.
Either staple fibres in the form of commercially available cardings or cards of continuous fibres are used to manufacture the fibre fleece. Whereas the fleece can be laid up using the procedures familiar to the practitioner skilled in the art, the aerogel granulate is scattered. Attention must be paid to achieving the most even possible distribution of the granulate grains when the aerogel granulate is introduced into the fibre composite. This can be done by using commercially available sprinkling apparatuses.
When a covering layer is used, it is possible to lay up the fibre fleece on a covering layer when the aerogel is being sprinkled on; once this process is ended, then the upper covering layer is put in place.
It covering layers that are of finer fibre material are used, the covering layer that is of fine fibres and/or bi-component fibres is laid up using known processes and optionally needled as described above; the fibre composite that contains the aerogel is then placed on this. For a further, upper covering layer, a layer can be laid up using fine fibres and/or bi-component fibres, as for the lower covering layer, and then optionally needled.
The resulting fibre composite is thermally bonded, optionally under pressure, at temperatures above the melting point of the fibre material that has the lowest melting point. The pressure is between normal pressure and the compressive strength of the aerogel that is used. The length of time that the temperature acts on the material is to be selected so as to ensure that only the surfaces of the fibres melt.
The complete processing procedures can, if preferred, be carried out continuously using installations familiar to the practitioner skilled in the art,
Because of their low thermal conductivity, the panels and mat according to the present invention are suitable for use as thermal insulation material.
In addition to this, the panels and mat according to the present invention can be used as sound absorbing material, either directly or in the form of resonance absorbers since they have a low acoustic velocity and, compared to monolithic aerogels, they provide greater acoustic attenuation. In addition to the damping effect of the aerogel material, depending on the permeability of the fibre fleece, there is also additional damping caused by air friction between the pores in the fibrous formation. The permeability of the fibre fleece can be adjusted by changing the diameter of the fibres, the density of the fleece, and the grains size of the aerogel particles. If the fibrous formation also contains covering layers, these covering layers should permit the sound waves to penetrate into the fibrous formation and not reflect the sound waves to any great extent.
In addition to the foregoing, because of the porosity of the fibrous formation and, in particular, the great porosity and the surface to volume ratio of the aerogels, the panels and mat according to the prevent invention are also suitable as adsorption materials for liquids, vapours, and gases. A specific adsorption effect can be achieved by modifying the surface of the aerogel.

Fibrous-formation aerogel composite material containing at least one thermoplastic fibrous material, process for the production thereof, and use thereof


A formaldehyde-free aqueous binder comprising

The present invention relates to the use of formaldehyde-free binders for producing shaped articles and boards from finely divided natural materials, for example wood chips, wood fibers, sisal fibers, jute fibres, flax fibers or cork chips.
Shaped articles, for example boards, are frequently produced from such renewable raw materials using formaldehyde condensation resins as binders. The disadvantage of these binders is the emission of formaldehyde not only during the manufacture of the boards and shaped articles but also during their later use.
EP 445 578 discloses shaped articles composed of finely divided materials (including wood fibers) in which condensation products of a mixture comprising at least one high molecular weight polycarboxylic acid and at least one polyfunctional amine, alkanolamine or alcohol are used as binders. The disclosed high molecular weight polycarboxylic acids are polyacrylic acid poly(methyl methacrylate-co-n-butyl acrylate-co-methacrylic acid) and poly(methyl methacrylate-co-methacrylic acid). The polyhydric alcohols and alkanolamines used are 2-hydroxymethyl-1,4-butanediol, trimethylolpropane, glycerol, poly (methyl methacrylate-co-hydroxypropyl acrylate), diethanolamine and triethanolamine. Maleic acid is mentioned as a possible comonomer for preparing the high molecular weight polycarboxylic acids, but the use of maleic acid copolymers is not more particularly described. Preference is given to the use of xcex1,xcex2-unsaturated carboxylic acids. The use of triethanolamine as crosslinker is mentioned in an Example, but only in combination with an aqueous dispersion of a copolymers of methyl methacrylate and methacrylic acid obtained in an emulsion polymerization.
However, the water resistance of the shaped wood-fiber articles described in EP 445 578 leaves something to be desired.
EP 583 086 discloses formaldehyde-free aqueous binders for producing mechanically stable, heat-resistant glass fiber webs. The binders comprise polycarboxylic acids, polyols and a phosphorus-containing reaction accelerant. There is no mention of the binder being used for binding finely divided natural materials.
EP 651 088 describes the bonding of cellulose substrates, especially fiber webs, with aqueous compositions of polycarboxylic acids, polyols and phosphorus-containing accelerants. The presence of phosphorus-containing compounds, for example sodium hypophosphite monohydrate, as reaction accelerant is mandatory in these binders.
The production of shaped articles, especially chipboard, is mentioned as a possible use; however, the use of maleic acid or maleic anhydride copolymers together with alkanolamines for this purpose is not disclosed.
It is an object of the present invention to provide highly reactive formaldehyde-free binders for producing boards and shaped articles from finely divided natural materials. The shaped articles and boards shall have good mechanical properties, especially low water swellability.
We have found that this object is achieved by the use of a formaldehyde-free aqueous binder comprising
A) a free-radically polymerized polymer containing from 5 to 100% by weight of units derived from an ethylenically unsaturated acid anhydride or from an ethylenically unsaturated dicarboxylic acid whose carboxyl groups can form an anhydride group, and
B) an alkanolamine having at least two hydroxyl groups,
as binder for renewable raw materials in the form of fibers or chips to produce shaped articles.
The present invention also provides shaped articles obtainable by the foregoing use.
The aqueous binder of this invention includes a polymer A) containing from 5 to 100% by weight, preferably from 5 to 50% by weight, particularly preferably from 10 to 40% by weight, of units derived from an ethylenically unsaturated acid anhydride or an ethylenically unsaturated dicarboxylic acid whose carboxyl groups are capable of forming an anhydride group hereinafter referred to as monomer a)).
The acid anhydrides are preferably dicarboxylic anhydrides. Suitable ethylenically unsaturated dicarboxylic acids are generally those having carboxylic acid groups on vicinal carbons. The carboxylic acid groups can also be present in the form of their salts.
Preferred monomers a) are maleic acid or maleic anhydride, itaconic acid, narbornenedicarboxylic acid 1,2,3,6-tetrahydrophthalic acid, 1,2,3,6-tetrahydrophthalic anhydride, their alkali metal and ammonium salts or mixtures thereof. Maleic acid and maleic anhydride are particularly preferred.
As well as monomer a), the polymer may additionally contain monomer b).
Monoethylenically unsaturated C3-C10-monocarboxylic acids, (monomer b1), for example acrylic acid, methacrylic acid, ethylacrylic acid, allylacetic acid, crotonic acid, vinylacetic acid, maleic monoesters such as methyl hydrogen maleate, their mixtures and their alkali metal and ammonium salts.
Linear 1-olefins, branched-chain 1-olefins or cyclic olefins (monomer b2), for example ethene, propene, butene, isobutene, pentene, cyclopentene, hexene, cyclohexene, octene, 2,4,4-trimethyl-1-pentene with or without 2,4,4-trimethyl-2-penten, C8-C10-olefin, 1-dodecene, C12-C14-olefin, octadecene, 1-eicosene (C20), C20-C24-olefin; metallocene-catalytically prepared oligoolefins having a terminal double bond, for example oligopropene, oligohexene and oligooctadecene; cationically polymerized olefins having a high xcex1-olefin content, for example polyisobutene.
Vinyl and allyl alkyl ethers having from 1 to 40 carbon atoms in the alkyl radical, which alkyl radical can carry further substituents such as hydroxyl, amino or dialkylamino or one or more alkoxylate groups (monomer b3), for example methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl cyclohexyl ether, vinyl-4-hydroxybutyl ether, decyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, 2-(diethylamino)ethyl vinyl ether, 2-(di-n-butylamino)ethyl vinyl ether, methyldiglycol vinyl ether and also the corresponding allyl ethers and mixtures thereof.
Acrylamides and alkyl-substituted acrylamides (monomer b4), for example acrylamide, methacrylamide, N-tert-butylacrylamide, N-methyl(meth)acrylamide.
Sulfo-containing monomers (monomer b5), for example allylsulfonic acid, methallylsulfonic acid, styrenesulfonate, vinylsulfonic acid, allyloxybenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and their corresponding alkali metal or ammonium salts or mixtures thereof.
C1-C8-Alkyl or C1-C4-hydroxyalkyl esters of acrylic acid, methacrylic acid or maleic acid, or acrylic, methacrylic or maleic esters of C1-C18-alcohols alkoxylated with from 2 to 50 mol of ethylene oxide, propylene oxide, butylene oxide; or mixtures thereof (monomer b6), for example methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 1,4-butanediol monoacrylate, dibutyl maleate, ethyldiglycol acrylate, methylpolyglycol acrylate (11 EO), (meth)acrylic esters of C13/C15-oxo alcohol reacted with 3,5,7,10 or 30 mol of ethylene oxide, or mixtures thereof.
Alkylaminoalkyl (meth)acrylates or alkylaminoalkyl (meth)acrylamides or quaternization products thereof (monomer b7), for example 2-(N,N-dimethylamino)ethyl (meth)acrylate, 3-(N,N-dimethylamino)propyl (meth)acrylate, 2-(N,N,N-trimethylammonio)ethyl (meth)acrylate chloride, 2-dimethylaminoethyl(meth)acrylamide, 3-dimethylaminopropyl (meth)acrylamide, 3-trimethylammoniopropyl(meth)acrylamide chloride.
Vinyl and allyl esters of C1-C30-monocarboxylic acids (monomer b8), for example vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl 2-ethylhexanoate, vinyl nonanoate, vinyl decanoate, vinyl pivalate, vinyl palmitate, vinyl stearate, vinyl laurate.
N-vinylformamide, N-vinyl-N-methylformamide, styrene, xcex1-methylstyrene, 3-methylstyrene, butadiene, N-vinylpyrrolidone, N-vinylimidazole, 1-vinyl-2-methylimidazole, 1-vinyl-2-methylimidazoline, N-vinylcaprolactam, acrylonitrile, methacrylonitrile, allyl alcohol, 2-vinylpyridine, 4-vinylpyridine, diallyldimethylammonium chloride, vinylidene chloride, vinyl chloride, acrolein, methacrolein and vinylcarbazole and mixtures thereof.
As well as monomer a), the polymer can additionally contain from 0 to 95% by weight of monomere b. Preferably, as well as monomer a), the polymer additionally contains monomer b in amounts from 50 to 95, particularly preferably from 60 to 90, % by weight.
Preferred monomers are acrylic acid, methacrylic acid, ethene, propene, butene, isobutene, cyclopentene, methyl vinyl ether, ethyl vinyl ether, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, vinyl acetate, styrene, butadiene, acrylonitrile and mixtures thereof.
Particular preference is given to acrylic acid, methacrylic acid, ethene, acrylamide, styrene and acrylonitrile and mixtures thereof.
Very particular preference is given to acrylic acid, methacrylic acid and acrylamide and mixtures thereof.
The polymers can be prepared according to customary polymerization processes, for example by mass, emulsion, suspension, dispersion, precipitation or solution polymerization. The polymerization processes mentioned are preferably carried out in the absence of oxygen, preferably in a stream of nitrogen. By whichever method the polymerization is carried out it is carried out in customary equipment, for example stirred tanks, stirred tank cascades, autoclaves, tubular reactors and kneaders. Preference is given to using the method of solution, emulsion, precipitation or suspension polymerization. The methods of solution and emulsion polymerization are particularly, preferred. The polymerization can be carried out in solvents or diluents, for example toluene, o-xylene, p-xylene, cumene, chlorobenzene, ethylbenzene, technical-grade mixtures of alkylaromatics, cyclohexane, technical-grade aliphatics mixtures, acetone, cyclohexanone, tetrahydrofuran, dioxane, glycols and glycol derivatives, polyalkylene glycols and derivatives thereof, diethyl ether, tert-butyl methyl ether, methyl acetate, isopropanol, ethanol, water or mixtures such as, for example, isopropanol/water mixtures. The preferred solvent or diluent is water with or without proportions of up to 60% by weight of alcohols or glycols. The use of water is particularly preferred.
The polymerization can be carried out at temperatures from 20 to 300xc2x0 C., preferably from 60 to 200xc2x0 C. Depending on the choice of polymerization conditions, it is possible to obtain weight average molecular weights for example within the range from 800 to 5 000 000, especially from 1 000 to 1 000 000. The weight average molecular weights Mw are preferably within the range from 2000 to 400 000. Mw is determined by gel permeation chromatography.
The polymerization is preferably carried out in the presence of compounds forming free radicals. These compounds are required in an amount of up to 30, preferably 0.05 to 15, particularly preferably from 0.2 to 8, % by weight, based on the monomers used in the polymerization. In the case of multicomponent initiator systems (eg. redox initiator systems), the foregoing weights are based on the sum total of the components.
Examples of suitable polymerization initiators are peroxides, hydroperoxides, peroxodisulfates, percarbonates, peroxyesters, hydrogen peroxide and azo compounds. Examples of initiators which can be water-soluble or else water-insoluble are hydrogen peroxide, dibenzoyl peroxide, dicyclohexyl peroxodicarbonate, dilauroyl peroxide, methyl ethyl ketone peroxide, di-tert-butyl peroxide, acetylacetone peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl perneodecanoate, tert-amyl perpivalate, tert-butyl perpivalate, tert-butyl perneohexanoate, tert-butyl per-2-ethylhexanoate, tert-butyl perbenzoate, lithium, sodium, potassium and ammonium peroxodisulfate, azodiisobutyronitrile, 2,2xe2x80x2-azobis(2-amidinopropane) dihydrochloride, 2-(carbamoylazo)isobutyronitrile and 4,4-azobis(4-cyanovaleric acid).
The initiators can be used alone or mixed with each or one another, for example mixtures of hydrogen peroxide and sodium peroxodisulfate. The polymerization in aqueous medium is preferably carried out using water-soluble initiators.
It is equally possible to use the known redox initiator systems as polymerization initiators. Such redox initiator systems include at least one peroxide-containing compound combined with a redox coinitiator, for example reducing sulfur compounds, for example bisulfites, sulfites, thiosulfates, dithionites and tetrathionates of alkali metals and ammonium compounds. For instance, combinations of peroxodisulfates with alkali metal or ammonium bisulfites can be used, for example ammonium peroxodisulfate and ammonium disulfite. The ratio of peroxide-containing compound to redox coinitiator is within the range from 30:1 to 0.05:1.
The initiators or redox initiator systems can be combined, in addition, with transition metal catalysts, for example salts of iron, cobalt, nickel, copper, vanadium and manganese. Examples of suitable salts are iron(II) sulfate, cobalt(II) chloride, nickel(II) sulfate, copper(I) chloride. Based on monomers, the reducing transition metal salt is used in a concentration of from 0.1 ppm to 1 000 ppm. For instance, combinations of hydrogen peroxide with iron(II) salts can be used, for example 0.5 to 30% of hydrogen peroxide with 0.1 to 500 ppm of Mohr""s salt.
Similarly, a polymerization in organic solvents can be carried out using the abovementioned initiators combined with redox coinitiators and/or transition metal catalysts, for example benzoin, dimethylaniline, ascorbic acid combined with solvent-soluble complexes of heavy metals, such as copper, cobalt, iron, manganese, nickel and chromium. The amounts of redox coinitiators or transition metal catalysts customarily used here customarily range from about 0.1 to 1 000 ppm, based on the amounts of the monomers used.
If the polymerization of the reaction mixture is started at the lower limit of the suitable temperature range for the polymerization and subsequently completed at a higher temperature, it is advantageous to use at least two different initiators which decompose at different temperatures, so that a sufficient concentration of free radicals is available within every temperature interval.
To prepare polymers having a low average molecular weight it is frequently advantageous to carry out the copolymerization in the presence of regulators. Customary regulators can be used for this, for example organic SH-containing compounds, such as 2-mercaptoethanol, 2-mercaptopropanol, mercaptoacetic acid, tert-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and tert-dodecyl mercaptan, C1-C4-aldehydes, such as formaldehyde, acetaldehyde, propionaldehyde, hydroxylammonium salts such as hydroxylammonium sulfate, formic acid, sodium bisulfite or isopropanol. The polymerization regulators are generally used in amounts from 0.1 to 10% by weight, based on the monomers. The average molecular weight can also be influenced by the choice of suitable solvent. For instance, polymerization in the presence of diluents having benzylic hydrogen atoms leads to a reduced average molecular weight due to chain transfer.
To prepare higher molecular weight copolymers it is frequently advantageous to carry out the polymerization in the presence of crosslinkers. Such crosslinkers are compounds having two or more ethylenically unsaturated groups, for example diacrylates or dimethacrylates of at least dihydric saturated alcohols, eg. ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,2-propylene glycol diacrylate, 1,2-propylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, neopentylglycol diacrylate, neopentylglycol dimethacrylate, 3-methylpentanediol diacrylate and 3-methylpentanediol dimethacrylate. Similarly the acrylic and methacrylic esters of alcohols having more than 2 OH groups can be used as crosslinkers, eg. trimethylolpropane triacrylate or trimethylolpropane trimethacrylate. A further class of crosslinkers are diacrylates or dimethacrylates of polyethylene glycols or polypropylene glycols having molecular weights from 200 to 9 000 in each case. Polyethylene glycols and polypropylene glycols used for preparing the diacrylates or dimethacrylates preferably have a molecular weight of from 400 to 2 000 in each case. As well as the homopolymers of ethylene oxide and propylene oxide it is also possible to use block copolymers of ethylene oxide and propylene oxide or copolymers of ethylene oxide and propylene oxide containing the ethylene oxide and propylene oxide units in random distribution. The oligomers of ethylene oxide or propylene oxide are also suitable for preparing the crosslinkers, eg. diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate and/or tetraethylene glycol dimethacrylate.
Suitable crosslinkers further include vinyl acrylate, vinyl methacrylate, vinyl itaconate, divinyl adipate, butanediol divinyl ether, trimethylolpropane trivinyl ether, allyl acrylate, allyl methacrylate, pentaerythritol triallyl ether, triallylsucrose, pentaallylsucrose, pentaallylsaccharose, methylenebis(meth)acrylamide, divinylethyleneurea, divinylpropyleneurea, divinylbenzene, divinyldioxane, triallyl cyanurate, tetraallylsilane, tetravinylsilane and bis- or polyacryloylsiloxanes (eg. Tegomers(copyright) from Th. Coldschmidt AG). The crosslinkers are preferably used in amounts from 10 ppm to 5% by weight, based on the monomers to be polymerized.
If the method of emulsion, precipitation, suspension or dispersion polymerization is used, it can be advantageous to stabilize the polymer droplets or particles by means of interface-active auxiliaries. Typically these are emulsifiers or protective colloids. Emulsifiers used can be anionic, nonionic, cationic or amphoteric. Examples of anionic emulsifiers are alkylbenzenesulfonic acids, sulfonated fatty acids, sulfosuccinates, fatty alcohol sulfates, alkylphenol sulfates and fatty alcohol ether sulfates. Examples of usable nonionic emulsifiers are alkylphenol ethoxylates, primary alcohol ethoxylates, fatty acid ethoxylates, alkanolamide ethoxylates, fatty amine ethoxylates, EO/PO block copolymers and alkylpolyglucosides. Examples of cationic and amphoteric emulsifiers used are quaternized amine alkoxylates, alkylbetaines, alkylamidobetaines and sulfobetaines.
Examples of typical protective colloids are cellulose derivatives, polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, polyvinyl acetate, polyvinyl alcohol, polyvinyl ether, starch and starch derivatives, dextran, polyvinylpyrrolidone, polyvinylpyridine, polyethyleneimine, polyvinylimidazole, polyvinylsuccinimide, polyvinyl-2-methylsuccinimide, polyvinyl-1,3-oxazolid-2-one, polyvinyl-2-methylimidazoline and maleic acid or anhydride copolymers as described for example in DE 2 501 123.
The emulsifiers or protective colloids are customarily used in concentrations from 0.05 to 20% by weight, based on the monomers.
If the polymerization is carried out in aqueous solution or dilution, the monomers can be wholly or partly neutralized with bases before or during the polymerization. Examples of suitable bases are alkali metal and alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium oxide, sodium carbonate; ammonia; primary, secondary and tertiary amines, such as ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, dimethylamine, diethylamine, di-n-propylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine and morpholine.
Polyacid amines can also be used for neutralization, for example ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propylenediamine, dimethylaminopropylamine, neopentanediamine, hexamethylenediamine, 4,9-dioxadodecane-1,12-diamine, polyethyleneimine or polyvinylamine.
Ammonia, triethanolamine and diethanolamine are preferred for partially or completely neutralizing the ethylenically unsaturated carboxylic acids before or during the polymerization.
The ethylenically unsaturated carboxylic acids are particularly preferably not neutralized before and during the polymerization. It is similarly preferred not to add a neutralizing agent after the polymerization either, apart from alkanolamine B). The polymerization can be carried out continuously or batchwise according to a multiplicity of variants. It is customary to introduce part of the monomers as initial charge, if necessary in a suitable diluent or solvent and in the absence or presence of an emulsifier, a protective colloid or further assistants, to provide a blanket of an inert gas, and to raise the temperature until the desired polymerization temperature is achieved. However, the initial charge may also be a suitable diluent alone. The free-radical initiator, further monomers and other assistants, for example regulators or crosslinkers, each in a diluent, if necessary, are metered in over a defined period. The addition times may differ in length. For example, the initiator may be added over a longer period than the monomer.
If the polymer is obtained in water following a solution polymerization, there is usually no need to separate off the solvent. If it is nonetheless desired to isolate the polymer, this can be done by spray drying, for example.
If the polymer is prepared by the method of solution, precipitation or suspension polymerization in a solvent or solvent mixture which is volatile in steam, the solvent can be removed by introducing steam into the reaction mixture in order that an aqueous solution or dispersion may be obtained in this way. The polymer can also be separated from the organic diluent by a drying process.
Polymers A) are preferably present in the form of an aqueous dispersion or solution having solids contents from preferably 10 to 80%, in particular from 40 to 65%, by weight.
Polymer A) can also be obtained by grafting maleic acid or maleic anhydride or a monomer mixture comprising maleic acid or maleic anhydride onto a grafting base. Examples of suitable grafting bases are monosaccharides, oligosaccharides, modified polysaccharides and alkylpolyglycol ethers. Such graft polymers are described for example in DE 4 003 172 and EP 116 930.
Component B) comprises alkanolamines having at least two OH groups. Preference is given to alkanolamines of the formula
where R1 is hydrogen, C1-C10-alkyl or C1-C10-hydroxyalkyl and R2 and R3 are each C1-C10-hydroxyalkyl.
It is particularly preferable for R2 and R3 to be independently of each other C2-C5-hydroxyalkyl and R1 to be hydrogen, C1-C5-alkyl or C2-C5-hydroxyalkyl.
Examples of suitable compounds of the formula I are diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, methyldiethanolamine, butyldiethanolamine and methyldiisopropanolamine. Triethanolamine is particularly preferred.
The formaldehyde-free binders of this invention are preferably prepared by using polymer A) and alkanolamine B) in such a relative ratio that the molar ratio of carboxyl groups of component A) to the hydroxyl groups of component B) is within the range from 20:1 to 1:1, preferably within the range from 8:1 to 5:1, particularly preferably within the range from 5:1 to 1.7:1 (anhydride groups are here calculated as 2 carboxyl groups).
The formaldehyde-free aqueous binders of this invention are prepared for example simply by adding the alkanolamine to the aqueous dispersion or solution of polymer A).
The binders of this invention preferably include less than 1.5% by weight, particularly preferably less than 1.0% by weight, very particularly preferably less than 0.5% by weight, especially less than 0.3% by weight, in particular less than 0.1% by weight, based on the sum of A)+B), of a phosphorus-containing reaction accelerant. Phosphorus-containing reaction accelerants are mentioned in U.S. Pat. No. 651,088 and U.S. Pat. No. 583,086. They are in particular alkali metal hypophosphites, phosphites, polyphosphates, dihydrogenphosphates, polyphosphoric acid, hypophosphoric acid, phosphoric acid, alkylphosphinic acid and oligomers and polymers of these salts and acids.
The binders of this invention preferably include no phosphorus-containing reaction accelerants, or amounts of a phosphorus-containing compound effective for reaction acceleration. The binders of this invention may include an esterification catalyst, for example sulfuric acid or p-toluenesulfonic acid or titanates or zirconates. The binders of this invention can be used as impregnants or coatings. The binders of this invention can be the sole constituent of said impregnants or coatings. However, the impregnants or coatings may additionally include further additives suitable for the particular intended use. Examples of suitable additives are dyes, pigments, biocides, hydrophobicizing agents, wetting agents, plasticizers, thickeners, adhesion improvers, reductants and transesterification catalysts.
The binders of this invention dry at 50xc2x0 C. in 72 hours to a film from 0.3 to 1 mm in thickness and, following a subsequent 15 minutes"" cure at 130xc2x0 C. in air, preferably have a gel content of above 50% by weight, particularly preferably of above 60% by weight, very particularly preferably above 70% by weight.
After curing, the cured films are stored at 23xc2x0 C. in water for 48 hours. Solubles remain in the water. The film is then dried at 50xc2x0 C. to constant weight and weighed. The weight corresponds to the gel content calculated in % by weight, based on the weight before the volatiles are separated off. Constant weight is achieved when the weight decrease over 3 hours is less than 0.5, in particular less than 0.1% by weight.
The binders are used for producing shaped articles from fibers or chips and may include further additives, for examples insecticides, fungicides or fillers, hydrophobicizing agents, such as silicone oils, paraffins, waxes, fatty soaps, water retention aids, wetting agents, flame retardants, such as borates and aluminum hydroxide. The chips or fibers can be chips or fibers composed of renewable raw materials or synthetic or natural fibers, for example from post-use clothing. Suitable renewable raw materials include in particular sisal, jute, flax, coil fibers, banana fibers, hemp and cork. Particular preference is given to wood fibers or wood chips.
The shaped articles preferably have a density of from 0.4 to 1.0 g/cm3 at 23xc2x0 C.
Contemplated shaped articles include boards. The boards are generally at least 1 mm, preferably at least 2 mm, in thickness. Also contemplated are automotive interior parts, for example door inner linings, dashboard members and parcel shelves.
The weight of binder used is generally from 0.5 to 40% by weight, preferably from 1 to 15% by weight (binder solids, calculated as sum of A)+B)), based on the fibers or chips.
The fibers or chips can be directly coated with the binder or mixed with the aqueous binders. The viscosity of the aqueous binder is preferably (especially for the production of shaped articles from wood fibers or wood chips) set to within the range from 10 to 10 000, particularly preferably from 50 to 1 500, very particularly preferably from 100 to 1 000, mPaxc2x7s (DIN 53019, rotary viscometer at 41 sec-1).
The mixture of fibers or chips and the binder can be predried for example at from 10 to 150xc2x0 C. and then be pressed for example at temperatures from 50 to 300xc2x0 C., preferably from 100 to 250xc2x0 C., particularly preferably from 140 to 225xc2x0 C., and pressures from generally 2 to 1000 bar, preferably from 10 to 750 bar, particularly preferably from 50 to 500 bar, to form shaped articles.
The binders are particularly suitable for producing woodbase materials such as wood chipboard and wood fiberboard (cf. Ullmann""s Encyclopxc3xa4die der technischen Chemie, 4th Edition 1976, Volume 12, p. 709-727), which can be produced by bonding subdivided wood, for example wood chips and wood fibers. The water resistance of woodbase materials can be increase by adding a commercially available aqueous paraffin dispersion or other hydrophobicizing agent to the binder or beforehand or subsequently to the fibers or chips.
The manufacture of chipboard is common knowledge and described for example in H. J. Deppe, K. Ernst Taschenbuch der Spanplattentechnik, 2nd Edition, Verlag Leinfelden 1982.
Preference is given to using chips whose average thickness is on average within the range from 0.1 to 2 mm, in particular from 0.2 to 0.5 mm, and which have a water content of less than 6% by weight. The binder which is applied as uniformly as possible to the wood chips using a weight ratio of binder:wood chip; based on the solids content (calculated as A)+B)), which is preferably within the range from 0.02:1 to 0.3:1. Uniform distribution is obtained for example by spraying a finely divided form of the binder onto the chips.
The resin-bound wood chips are then sprinkled out to form a layer with a very uniform surface, the thickness of the layer depending on the thickness desired for the ready-produced chipboard. The sprinkled layer is pressed at a temperature of for example from 100 to 250xc2x0 C., preferably from 140 to 225xc2x0 C. and pressures of customarily from 10 to 750 bar to form a dimensionally stable board. The pressing times required can vary between wide limits and are generally within the range from 15 seconds to 30 minutes.
The wood fibers of suitable quality required for manufacturing medium density fiberboard (MDF) from the binders can be produced by grinding bark-free wood chips in special mills or refiners at about 180xc2x0 C.
To apply binder to them, the wood fibers are generally suspended in an air stream and the binder blown into the resulting fiber stream (xe2x80x9cblow-linexe2x80x9d process). The ratio of wood fiber to binder based on the dry content and solids content, respectively, is customarily within the range from 40:1 to 3:1, preferably within the range from 20:1 to 4:1. The resin-bound fibers are dried in the fiber stream at from 130 to 180xc2x0 C., for example, sprinkled out to form a fiber web and compressed at pressures from 20 to 40 bar to form boards or shaped articles.
The resin-bound wood fibers can also, as described for example in DE-A-2 417 243, be processed to form a transportable fiber mat. This semifabricate can then be further processed in a second, spatially and chronologically separate step, to form plates or moldings, for example door inner linings of automotive vehicles.
The binders of this invention are also suitable for manufacturing plywood and carpentry board according to the commonly known manufacturing processes.
Other natural fiber materials such as sisal, jute, hemp, flax, coil fibers, banana fibers and other natural fibers can be processed into boards and shaped articles using the binders. The natural fiber materials can also be used in mixtures with synthetic fibers, for example polypropylene, polyethylene, polyester, polyamides or polyacrylonitrile. In effect, these synthetic fibers can also act as cobinders alongside the binder of this invention. The proportion of synthetic fiber in this instance is preferably less than 50% by weight, in particular less than 30% by weight, very particularly preferably less than 10% by weight, based on all chips or fibers. The fibers can be processed by the wood fiberboard method. However, it is also possible for preformed natural fiber mats to be impregnated with the binders of this invention with or without the addition of a wetting aid. The impregnated mats are then pressed in the binder-moist or predried state, for example at temperatures within the range from 100 to 250xc2x0 C. and pressures within the range from 10 to 100 bar, to form boards or moldings.
The shaped articles obtained according to this invention have low water absorption, low thickness swelling after water aging and high strength and are formaldehyde-free.

Formaldehyde-free binders for shaped articles

Abstract: is useful as binder for renewable raw materials in the form of fibers or chips to produce shaped articles.