CA1051294A

CA1051294A - Heat sealable sheet materials

Info

Publication number: CA1051294A
Application number: CA199,808A
Authority: CA
Inventors: Eckart Reese; Joachim Wank
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1973-05-16
Filing date: 1974-05-14
Publication date: 1979-03-27
Also published as: AT331040B; FR2229528B1; ATA397674A; ES426301A1; GB1430712A; FR2229528A1; JPS5015873A; DE2324715A1; NL7406412A

Abstract

HEAT SEALABLE SHEET MATERIALS

Abstract of the Disclosure A process for the production of a heat sealable temperature-resistant sheet material wherein a solution of a partially fluorinated high-molecular weight aliphatic hydro-carbon with a molecular weight of 1,000 to 500,000 which is solid at room temperature in a solvent mixture of a) 10 to 60 volume percent of at least one chlorinated aliphatic hydrocarbon containing 1 to 6 carbon atoms and having a boiling point of 30 to 150°C and b) 40 to 90 volume percent of at least one alkyl ester of a polybasic aromatic carboxylic acid or at least one high-boiling ketone is applied to a temperature-resistant plastics sheet and the solvent is removed.

Description

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It is known that high temperature resistant plastics sheets, for example polyimide sheets coated with fluorinated hydrocarbons which are solid at room temperature are capable of being heat-sealed. m e layer of fluorinated hydrocarbons is generally produced by laminating the temperature-resistant sheet to a sheet of the fluorinated hydrocarbon at a tempera-ture above the softening point of the fluorinated hydrocarbon.
Another method consists of applying the fluorinated hydrocar-bon in the form o~ a powder to the temperature-resistant sheet and then fixing the powder by sintering. Attempts have also been made to dissolve the fluorinated hydrocarbon in high boi-ling solvents, to apply the solution to the temperature-resi-stant sheet and then evaporate the solvent. This method re-quires high drying temperatures and long drying times and the finished sheet must be finally tempered at temperatures above 200C. Furthermore, additives must be added to the solution of fluorinated hydrocarbon to improve film-formation. These addi-tives must be completely removed with the solvent or at the tempering stage. me formation of a perfect coating by this method is difficult and very complicated.
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- ~ This invention relates to a new process for producing temperature-resistant sheet materials which are capable of : being heat-sealed, using a coating of fluorinated hydrocarbons, , ~ wherein a solution of a partially fluorinated, high-molecular i weight aliphatic hydrocarbon with a molecular weight of 1000 to 500,000 which is solid at room temperature, a solvent mixture - of a) 10 to 60 volumes percent of a chlorinated aliphatic hydro-carbon containing 1 to 6 carbon atoms and having a boiling point of 30 - 150C and '.;~

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b) 40 - 90 volumes percent of an alkyl ester of a polybasic aromatic carboxylic acid or high boiling ketones is applied to a temperature-resistant plastics sheet and the solvent is removed.
Preferred solvent mixtures are those which at least at their boiling point are capable of swelling the temperature-resistant sheet and thus producing a firm bond between the temperature-resistant sheet and the layer of fluorinated hydro-carbon.
The solvent mixtures used for dissolving the fluorina-ted hydrocarbons generally consist of 10 to 60 volumes percent of a low-boiling chlorinated hydrocarbon which contains 1 to 6 carbon atoms and 40 to 90 volumes percent of an alkyl ester ~ of a polybasic aromatic carboxylic acid or high-boiling ke-; 15 tones.
~; Low-boiling chlorinated hydrocarbons which have a boi-; ling point between ~0 and 150C is 1,1,1-trichloroethane.
Suitable alkyl esters of polybasic aromatlc carboxylic acids, preferably of di-, tri- or tetracarboxylic acids, are, for example, C1 - C18 alkyl esters Or phthalic acid, trimel-litic acid and benzene tetracarboxylic acid. Dimethyl phtha-late, dioctyl phthalate and phorone are particularly suitable.
The solution of fluorinated hydrocarbons in such solvent mix-tures generally contains 10 to 25~ of fluorinated hydrocarbons.
Suitable high boiling ketones are those having a boi-ling point between 80 and 250C, such as aliphatic ketones containing from 5 to 11 carbon atoms, pre~erably phorone, ~s~ aliphatic aromatic ketones containing from 7 to 1~ carbon atoms, preferred phenoxy acetone, or aromatic ketones con-~0 taining 7 to 13 carbon atoms, preferred diphenyl ketone.
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A most preferred solvent mixture consists of 10 to 60 volume percent of l,l,l-trichloroethane and of 40 to 90 volume percent of dimethylphthalate.
Fluorinated hydrocarbons which are particularly suitable for the coating are high-molecular weight ali-phatic compounds with molecular weights of about 1000 to about 500,000. Preferably 25 - 75% of the hydrogen atoms are replaced by fluorine. Up to 10% of the hydrogen atoms which are capable of being substituted may also be sub-stituted with other substituents which are stable at the reaction temperature, for example chlorine. The fluorinated hydrocarbons must be solid at room tempera-ture.
Particularly suitable fluorinated hydrocarbons are fluorinated ethylene-propylene copolymers with a molecular weight of about 1000 to about 500,000 which are composed of about 80 to 20% by weight of ethylene units and 20 to 80%
by weight of propylene units and in which 25 to 75% of ~ the hydrogen atoms are substituted with fluorine. Polyvinyli-- 20 dene fluorides with a molecular weight of about 1000 to about 10,000 are also particularly suitable.
The basic material used may in principle be any high-temperature resistant plastics sheet. Polyhydantoin f sheets are particularly suitable. Polyhydantoins arealready known. They may be prepared, for example, by reacting aromatic diglycine esters with diisocyanates.
A typical example is the reaction of N,N'-bis-carbethoxy-methyl-4,4'-diamino-diphenylmethane with 4,4'-diisocyanato-diphenylmethane. Polyhydantoins and methods of preparing them have been described, for example, in U.S. Patent Specification No. 3,397,253.
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To carry out the process, a sheet is produced from a temperature-resistant synthetic resinJ preferably a poly-hydantoin. The thickness of the sheet is generally about 5 to about 2001u . The solution of fluorinated hydrocarbon in the above described solvent mixture is applied to this sheet and the solvent is evaporated. The quantity of solution applied is calculated to produce a coating with a thickness of preferably 2 to 30~u. The solution of fluorinated hydrocarbons may be applied by any known methods, preferably by means of a roll coater or doctor knife. Temperatures of about 120 - 200C are in most cases required for evaporating the solvent.
Another object of this invention is a polyhydantoin sheet with a thickness of about 5 to about 200/u which carries a coating about 2 to about 30 ~ in thickness which is firmly bonded to the sheet and which consists of a partially fluorinated high-molecular weight aliphatic hydrocarbon with a molecular weight of 1000 to 500,000.
This sheet material is suitable in particular for use as an electro-insulating sheet. Coated sheets of other high-temperature resistant plastics are also suitable for this purpose but coated polyhydantoin sheets are preferred because they have an exceptionally high electrical insula-5 ~ tion value and exceptionally high break-down voltage. In , addition, their mechanical strength is exceptionally high.
,! The polyhydantoin sheets coated with fluorinated hydro-carbons according to the invention are used particularly ; for insulating flat copper conductors. They are wound spirally round such conductors and then sealed by heat.
Flat copper conductors of this kind are used for the field ;

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At ., , . L A 15 062 - 5 -,., Exam~le 1 -An ethylene-propylene copolymer with a molecular weight of about 50,000 which i9 composed of 50~ ethylene units and 50% propylene units and in which half the hydro-gen atoms which are capable of being subst~tuted are re-placed by fluorine atoms is dissolved in a mixture of 50 parts by ~olume of 1~ trichloroethane and 50 parts by volume of dimethyl phthalate at temperatures of 50 - 60C
to form a 10% by weight ~olution~ The filtered solution i~ coated by spreading on a polyhydantoin sheet 20 - 30 in thickne~s to form on it a layer with a thickness oi about 100 p. The coated sheet is dried in hot air at about 150C.
The coated polyhydantoin sheet obtained in this way carries a fluorinated hydrocarbon layer 10 ~ in thickness which adheres so firmly to the polyhydantoin æheet that , the ~trength of the bond is greater than the tear resistance - of the fluorinated hydrocarbon layerO
he coated ~heet i8 wound spirally round a flat copper conductor and sealed by heating to 250 - 300C. ~he insulated flat conductor obtained in this way can be twisted ~pirally without the insulating layer becoming detached.

Example 2 ` ~xample 1 i~ repeated except that a polyvinylidene r 25 fluoride with a molecular weight of about 1000 i8 used ~- instead of the fluorinated ethylene-propylene copolymer.
Here again the in~ulation obtained on the flat copper con-ductor is not detached by twisting.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

l. A process for the production of a heat sealable high tempera-ture-resistant sheet material wherein a solution of a partially fluorinated high-molecular weight aliphatic hydrocarbon with a molecular weight of 1000 to 500,000 which is solid at room temperature in a solvent mixture of a) 10 - 60 Vol.-% of at least one chlorinated aliphatic hydrocarbon con-taining 1 - 6 carbon atoms and having a boiling point of 30 - 150°C and b) 40 - 90 Vol.-% of at least one alkyl ester of a polybasic aromatic carboxylic acid or at least one high-boiling ketone is applied to a temperature-resistant plastics sheet and the solvent is removed.
2. A process as claimed in claim 1, wherein the plastics sheet is a polyhydantoin sheet.
3. A process as claimed in claim 1, wherein the plastics sheet is 5 to 200 µ thick.
4. A process as claimed in claim 1, wherein the partially fluorin-ated hydrocarbon is a partially fluorinated ethylene-propylene copolymer.
5. A process as claimed in claim 1, wherein the partially fluorinated hydrocarbon is a polyvinylidene fluoride.
6 A process as claimed in claim 1, wherein the alkyl ester is an ester of a benzene di-, tri- or tetracarboxylic acid and an aliphatic alcohol having 1 to 18 carbon atoms.
7. A process as claimed in claim 1, wherein the solvent mixture consists of 10 to 60 Vol.-% of 1,1,1-trichloroethane and 40 to 90 Vol.-%
of dimethylphthalate.
8. Heat sealable sheet materials consisting essentially of a polyhydantoin sheet having a thickness of about 5 to about 200 µ
and a coating firmly bonded to the sheet, which coating consists of a partially fluorinated high-molecular weight ali-phatic hydrocarbon with a molecular weight of 1000 to 500,000 and has a thickness of about 2 to about 30?.