CA1163543A - Method for the lamination of foam including a reinforcing scrim - Google Patents

Method for the lamination of foam including a reinforcing scrim

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Publication number
CA1163543A
CA1163543A CA000367736A CA367736A CA1163543A CA 1163543 A CA1163543 A CA 1163543A CA 000367736 A CA000367736 A CA 000367736A CA 367736 A CA367736 A CA 367736A CA 1163543 A CA1163543 A CA 1163543A
Authority
CA
Canada
Prior art keywords
scrim
heating element
foam
heating
adjacent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000367736A
Other languages
French (fr)
Inventor
Robert A. Ii Hay
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Priority to CA000367736A priority Critical patent/CA1163543A/en
Application granted granted Critical
Publication of CA1163543A publication Critical patent/CA1163543A/en
Expired legal-status Critical Current

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Abstract

ABSTRACT

Thermoplastic foam bodies are laminated together with a joint therebetween containing a rein-forcing scrim. Friction during the conveyance of the foam bodies past a heating assembly is equalized by passing the scrim through the heating assembly.

27,634B-F

Description

3 5 ~ 3 METHOD FOR L~MINATING FOAM BODIES
I~CLUDING A REINFORCING SCRIM

The present invention resides in an improved method for the preparation of laminated synthetic resinous thermoplastic foam bodies which incorporate a reinforcing scrim therein.

More particularly, the present invention resid~s in an improved method for the preparation of thermoplas~ic ~oam laminates wherein an undesirable bowing or curvature of the laminate is avoided.

Frequently, it is desired to laminate bodies of synthetic resinous thermoplastic fo~m together by passing a heated blade therebetween to heat-plastify adjacent surfaces o~ the bodies. The adjacent surfaces are then pre~sed toyether to fuse the surfaces together to provide a laminated body of the desired size. For many processes, it is desirable to incorporate within such a laminate a reinforcing scrim such as a glass fiber reinforcing scrim. Such laminates may be employed for the insulation of cryogenic vessels by the so-called spiral generation technique. Such a technique is dis-closed in U.S. Patent Nos. 4,017,346 and 4,050,607. An 27,634B-F -l-i635~3 apparatus for preparing laminates suitable for the spiral generation process is set forth in ~nited S-tates Patent No.
4,049,852 while various configurations of laminates suitable for the spiral generation process are set forth in United States Patent Nos. 3,919,034; 3,924,039; and 3,954,539. OEtentimes, such laminates, after preparation, show a somewhat cur~ed configuration along the longitudinal axis. The reason for the development of such undesired curvature ~as not understood and when it occurred it was frequently in an undesired direction which necessitated extra mechanical manipulation of the laminate, also referred to in the art as a billet or log, in order to have it conform to the desired configuration. In the thermal insulation for cyrogenic vessels, undesired mechanically induced tensila stresses in the insulation should be avoided in order to minimize the possibility of the insulating laminate cracking under thermal stress.
The invention resides in a generally continuous method for the preparation of an elongate laminate from a plurality of foam bodies formed from a synthetic resinous thermoplastic material having a reinforcing scrim embedded between said foam bodies, including the steps of heating adjacent surfaces of adjacent foam bodies to a temperature sufficient to plasticize the foam body surfaces, contacting the adjacent heated and plasticized surfaces of the foam bodies, and cooling the plasticized surfaces to form a rigid bond between the foam bodies incorporating the reinforcing scrim therein, the reinforcing scrim being positioned relative to the major surfaces of a planar heating element during the heating of the adjacent foam surfaces whereby a first portion of the scrim is in frictional contact with one surface of the heating element
-2-
3 ~ ~ 3 and a second portion of the scrim is in frictional contact with an opposite surface of the heating element, to thereby obtain a laminate exhibiting a desired degree of curvature.

-2a-;~, .

-2b-3 5 d~ 3 The invention further resides in a continu-ous method for the preparation of an elongate laminate of synthetic resinous, thermoplastic foam body incor-porating a reinforcing scrim therein, wherein adjacent foam surfaces of adjacent foam bodies are heated by means of a generally planar heating element having first and second oppo~ed heating surfaces to a temper-ature sufficient that on contact of the adjacent foam surfaces and ~ooling thereof, a rigid bond is achieved between the bodies the improvement which comprises pass-ing the reinforcing scrim, the scrim being in the form of one scrim folded over the heating element or the scrim comprising two separate portions, a portion dis-posed on each of the major heating surfaces, over the major surfaces uf ~he planar heating element during the heating of the adjacent foam surfaces to thereby obtain a lamina~e exhibiting a d~sixed degree of curva-ture.

The method of the present invention will become more apparent from the following specification taken in co~nection with ~he drawing wherein:

~ igure 1 is a schematic side view of a lami~ation apparatus in acccrdan e with the invention;

Figure 2 is a top view of the lamination apparatus of Figure l;

Figure 3 is a partly-disassembled heating blade assembly as used in the apparatus of the invention;

Figure 4 is a sectional view of the heating blade of the ~ssembly of Figure 3 showing the passage of a reinforcing scrim therethrough; and 27,634B-F -2b-3 S ~L 3 Figure 5 is a sectional view of an embodiment of the present invention in which a pair of heating blades are employed.

In Figures 1 and 2 there is schematically depicted a laminating apparatus 10 comprising in coopera-tive combination a frame and support means (not shown).
Supported on the frame is a supply roll 11 for dispensing therefrom a reinforcing scrim 12. The reinforcing scrim 12 extends between a first series of foam bodies formed from a synthetic resinous material 13 arranyed in end to-end relationship and a second series of foam bodies 14 also formed from a synthetic resinous material.
The foam bodies 13 and 14 have adjacent surfaces with the scrim 12 disposed therebetween. A first pair of 15 feed rolls 15 and 16 con~ey the foam bodies 13, 14 and the scrim 12 toward a second pair of pressure or feed rolls 18 and 19. ~djacent the feed rolls 18 and 19 and remote from the feed rolls 15 and 16 is a heating blade or platen assembly 21. It is preferred to support the scrim 12 between roll 11 and blade assembly 21 with a smooth sheet metal plate (not shown) ~o prevent wrinkling or folding of the scrim. The blade assembly 21 includes a heating element or blade 22 which passes be~ween the foam bodies 13 and 14 and raises the temperature of the adjacent surfaces of the foam bodies 13 and 14 to a temperature sufficient to heat-plastify and collapse the foam material. The foam bodies 13 and 14 are remo~ed from the region of the blade assembly 21 by first and second pairs of draw rolls 23, 24 and 25, 26.
The draw rolls force the heated surfaces o the foam bodies together, to thereby encapsulate the scrim within the heat plastified collapsed foam and between the foam bodies. It will be understood that the heat 27,634B-F -3-, 635~3 plasticized material of the foam bodies will readily pass or flow through the mesh or open spaces provided between the strands of the scrim to meld into each other to thereby unite into a combined layer of the plasticized material with the scrim embedded in the meld. Upon cooling, the plasticized material with the reinforcing scrim substan~ially centrally disposed therein is rigidified to permanently fuse the foam bodies to each other.

In Figure 3 there is depicted a view of a heating blade assembly 21 having an electrical resis-tance heating element 22 of generally flat planar configuration. The heating element 22 is perforated in regions where the maximum generation of heat is desired and may be of a substantially square or r~ctangular conXiguration. The thickness of the heating element is not critical provided that the thickness is sufficient to provide adequate strength during use and provided -that the voltage applied to the plate will produce a current flow sufficient to heat the plate to a tempera-ture sufficient to plasticize or melt the adjacent surfaces of the foam bodies. In a preferred embodiment, the heating element is shaped in a serpentine configuration, somewhat as illustrated in Figure 3. Such serpentine heating elements are well ~nown in th art. The heating element 22 is supported within a first frame or support membar 32 and is suitably insulated therefrom. The heating element is affi~ed to the support member 32 by means of screws 33 which are also electrically insulated from the heating element 22. Remotely disposed from ~he first support member 32 is a second support member 34, of which the bottom half only is shown. The heating element 22 is eiectrically insulated from the support 27,634B-F -4-5 ~ 3 ~5-member 34 by means of insulating material 36 such as a glass cloth-siloxane resin laminate.

A sectional view through the heating element 22 is depicted in Figure 4 wherein a reinforcing scrim 12a is shown passing through a central ~ransversely disposed slot 37 of the element 22. sy passing the reinforcing scrim 12a through the centrally disposed slot of the heating element, the frictional drag on adjacent surfaces of the foam bodies being laminated is approximately equalized such that the tendency for the resultant laminate to warp is substantially reduced.

In Figure 5 there is depicted a sectional view of an alternate heating assembly 40 suitable for the practice o~ the present invention. The heating assembly 40 comprises a first electrical resistance heating element 41 and a like heating element 42 in spaced apart parallel face-to-face relationship with element 41. Preferably, the heating elements have a serpentine configuration such as is illustrated for the heating element of Figure 3. Con~igurations for the heating element other than the preferred serpentine shape may be used and will be readily apparent to persons skilled in the art. Thus, a single reversely bent or U-shaped element could be satisactorily employed in the practice of the invention. Heating elements ~1 and 42 are separated by a plurality of spacers 43 of like discoidal configuration. The spacers 43 are disposed at the terminal ends or xeverse bénds in the heating elements and correspond in location generally to the support members 32 and 34 of Figure 3. Thus, the heating elements of Figure 5 are, ln essence, two heating elements such as are depicted in Figures 3 and 27,634B-F -5-, ~ ~35~3
4 but are positioned in a spaced-apart relat.ionship from each other to provide a path for a reinforcing scrim 12b to be passed therebetween. Preferably, the heating elements for use in the practice of the inven-tion have major opposed parallel faces and have athickness not greater than one-quarter inch and prefer-ably about 3/16 of an inch.

The heating element 22 of Figure 3 is preferably prepared from a perforated stainless steel sheet having a thickness of about 1/8 inch and the heating element 40 of Fi~ure 5 is prepared from perforated stainless steel sheets each having a thickness of about 1/16 of an inch ànd spaced about 1/16 of an inch apart to permit the passage therebetween of the reinforcing 1~ scrim 12b. For the lamination of polystyrene foam having a density of about two (2) pounds per cubic foot, the heating elements are heated to a temperature, as indicated by a thermocouple manually positioned on the surface of the heating element to a temperature of about 600F. A convenient source of electrical power for the heating element is an alternating current or direct current welding power supply.

The method of the present invention is useful with any synthetic resinous thermoplastic foam material which is heat-weldable and provides laminates having a minimum warp or curvature. The reinforcing scrim may be wider, narrower or egual in width to the faces of the foam bodies being laminated depending on the desired end use. The scrim may be continuous as depic~ed in Figures 1 and 2 or consist of a plurality of overlapping joined lengths. Conveniently, short lengths are joined at each end of a scrim section by a transversely extending 27,634B-F -6-~, -3 ~ ~ 3 pressure sensitive adhesive tape or other desired securing means. In the preparation of elongate laminates for use in the application of thermal insula-tion by the so-called spiral generation process, it is S highly desirable to maintain the curvature of the laminate at a value which is equal to or less than the curvature of the vessel wall to which it is applled.

The pre~ent invention is particularly suited ~or the pre~aration of laminated foam bodies of a synthetic resinous thermoplastic material for use in the insulation of cryogenic vessels. A typical laminate might comprise 5 pieces or planks of foam; for example, one 2 by 8 inch plank laminated to four 2 by 6 inch planks wherein the 2 by 6 inch planks are stacked four high, and one of the edges of each 2 by 6 inch plank is heat sealed to one face of the 2 by 8 inch plank to provide an 8 inch by 8 i~ch square laminate having a reinforcing scrim encapsulated in the sealed inner face of the 2 by 8 inch plank. A simpler laminate might comprise two 4 by a inch planks in welded ace~to-face engagement with a reinforcing scrim therebetween. In the preparation of laminates, a substantial problem has been observed in that wA~n two planks are laminated together by the use of a hot blade, and a scrim is supplied and em~edded within the weld between the two planks, an undesirable curvature or warpage is obtained in the resulting laminate. The present invention substantially reduces or eliminates such undesired curvature or warpage.

In its broadest application, it has been discovered that by passing the scrim through a planar heating assembly, the curvature or warpage o~ the 27,634B~F -7-63~43 laminate is substantially and signiflcantly reduced.
The mechanism by which this reduction in curvature is obtained is believed to be basically due to the balancing of frictional forces against each other on the opposed faces of the foam bodies to be joined.

By passing the scrim through an elec~rically heated blade or between a pair of such blades, the frictional drag on the foam bodies being laminated is equalized. The ~ond be~wee~ the foam bodies is obtained by heating the adjacent faces of foam bodies to plastify, i.e., to soften or melt the material and then contacting such heated foam faces under pressure. Heating of the scrim itself has little or no effect on the degree of bonding between the foam bodies. When a foam body is pushed or pulled through a heating assembly and the foam bodies to be laminated move relatlve to the heated blade or blade , friction is developed between the faces of the foam bodies contacting the fixed blade or blades. When a single blade is used, for example, in such a lamination procedure, one has the choice of placing a reinforcing scrim to be encapsulated in the weld line on one side or the other of the heated blade.
Accordingly, on one side o the blade, the foam body is in direct contact with the heating blade and on the other side of the blade, the reinforcing scrim is in direct contact with the blade and, accordingly, the frictional forces are different on opposite sides of the heating blade.

Rectangular foam bodies to be laminated, as in the apparatus of Figures 1 and 2, are bonded, that is, heat sealed or welded across the entire contiguous surfaces of the foam bodies. As the ad~acent faces of 27,634B-F -8-3 5 ~ 3 the foam bodies are heated to a tempera-ture at which they will bond to each other, the scrim is encapsulated or embedded therein. A portion of the scrim would only be free to move in the event that a foam surface to be laminated has voids therein such as grooves, cut-outs and the like.

It is apparent from the foregoing specification that the present invention is intended to be illustrative and is not to be construed as being restrictive or otherwise limiting excepting as it is set forth and defined in the appended claims.

27,634B-F -9-

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A generally continuous method for the preparation of an elongate laminate from a plurality of foam bodies formed from a synthetic resinous thermoplastic material having a reinforcing scrim embedded between said foam bodies, including the steps of heating adjacent surfaces of adjacent foam bodies to a temperature sufficient to plasticize the foam body surfaces, contacting the adjacent heated and plasticized surfaces of the foam bodies, and cooling the plasticized surfaces to form a rigid bond between the foam bodies incorporating the reinforcing scrim therein, the reinforcing scrim being positioned relative to the major surfaces of a planar heating element during the heating of the adjacent foam surfaces whereby a first portion of the scrim is in frictional contact with one surface of the heating element and a second por-tion of the scrim is in frictional contact with an opposite surface of the heating element, to thereby obtain a laminate exhibiting a desired degree of curvature.
2. The method of Claim 1, wherein the heating element is a generally flat sheet having a substantially serpentine configura-tion.
3. The method of Claim 2, wherein the scrim is passed substantially centrally through the heating element.
4. The method of Claim 3, wherein the scrim is passed from a first side to a second side of the heating element.
5. The method of Claim 1, wherein the heat-ing element comprises a pair of spaced-apart planar blade members and the scrim is passed therebetween.
6. The method of Claim 1, wherein the heat-ing element comprises a planar blade member, providing a slot in said blade member, and passing said scrim through the slot.
7. The method of Claim 6, wherein the slot is positioned substantially centrally of the planar blade member.
8. In a generally continuous method for the preparation of an elongate laminate of synthetic resin-ous, thermoplastic foam body incorporating a reinforc-ing scrim therein, wherein adjacent foam surfaces of adjacent foam bodies are heated by means of a generally planar heating element having first and second opposed heating surfaces to a temperature sufficient that on contact of the adjacent foam surfaces and cooling thereof, a rigid bond is achieved between the bodies the improvement which comprises passing the reinforc-ing scrim, the scrim being in the form of one scrim folded over the heating element or the scrim compris-ing two separate portions, a portion disposed on each 27,634B-F -11-of the major heating surfaces, over the major surfaces of the planar heating element during the heating of the adjacent foam surfaces to thereby obtain a laminate exhibiting a desired degree of curvature.

27,634B-F -12-
CA000367736A 1980-12-30 1980-12-30 Method for the lamination of foam including a reinforcing scrim Expired CA1163543A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000367736A CA1163543A (en) 1980-12-30 1980-12-30 Method for the lamination of foam including a reinforcing scrim

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000367736A CA1163543A (en) 1980-12-30 1980-12-30 Method for the lamination of foam including a reinforcing scrim

Publications (1)

Publication Number Publication Date
CA1163543A true CA1163543A (en) 1984-03-13

Family

ID=4118803

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000367736A Expired CA1163543A (en) 1980-12-30 1980-12-30 Method for the lamination of foam including a reinforcing scrim

Country Status (1)

Country Link
CA (1) CA1163543A (en)

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