DE2163963A1 - Insulating films and processes for their manufacture - Google Patents

Description

DR. M. KÖHLER DIPL-ING. C GERNHARDT 2163963

TELEGRAMS: KARFATENT NUSSBAUMSTRASSE 10

22nd December 1971

V. 40 956/71

Teijjin Limited Osaka, Japan

Insulating films and processes for their manufacture

The invention relates to insulating films or. -foil intended for long-term use under high Temperatures are suitable and have excellent electrical insulating properties and satisfactory physical properties Have properties.

It is known that polyethylene-2,6-naphthale.t

is an orientable, crystalline polymer / which is used for

or foil is suitable for deformation of filaments or film, and that its second transition point about 11O ⁰ C, ie, about 50 ° C higher than the second transition point. Polyethylene terephthalate is, as well as that its melting point about 270 ° C, ie about 10 ⁰ C higher
Is polyethylene terephthalate.

270 ^o C, ie about 10 C higher than the melting point of

It has been more than twenty years since this polymer became known (see the description exercise of British patent specification No. 604 073), but few proposals for the production have been more oriented Sheets made from this polymer. So far

209835/1058

known, was only the production of a film made of polyethylene terephthalate, the 2,6-naphthalenecarboxylate with a proportion of less than 25% of the repeating structural units of the polymer includes, in the description of the US patent ift Mr. 3 161 710 suggested. However, it can come from such a copolyester cannot produce an insulating film which is excellent at the same time Electro-insulating properties and has sufficient physical properties to withstand perpetual To withstand use under high temperatures, as this is the purpose of the invention.

In the specification of US Pat. No. 3,344, a magnetic recording ^{tape is proposed / Sas TE 5} ethylene-2,6-phthalate is used as the backing layer. According to this proposal, a biaxially oriented film made of polyethylene-2,6-rlaphthalate is subjected to a thermosetting or crystallization process with protection against shrinkage at a temperature of usually more than 120.degree. C. to au. about 250 ⁰ C or in some cases also more, preferably at 200-240 ⁰ C, subjected. The thermoset film can be thermally relaxed within * the same temperature range without any anti-shrinkage measures. It is proposed that said biaxial stretching of unstretched film by stretching the film at 105 - 150 ° C (preferably 115 - 140 ° C) in longitudinal

•,. *. rr r- -... ¹ SP ¹¹ L r- «times

direction from about 3J5-his \ about 6.0 ([preferably from 4.0 to 5> 5 times) its original length and to the chli dining stretching the film, advantageously enough, at 105-150 ⁰ C (preferably 115-140 ° C) in _ ^ o ^ ejt ^ BreitenrjLclitjinjs' -bis ,
Transverse direction / from about 3 - / about 1.4 times (preferably

209835/105 «

~ '~ 2Ί63963

from about 1.0 to about 1.3 times) its original

Transverse / borrowed width, i.e. from about 0% / elongation to about

40% transverse stretching. The film which has been biaxially oriented and post-heat treated in this way is then with a non-magnetic binder in which magnetizable particles of F ^ O, or the like are magnetic sensitive. Material dispersed, coated.

Research has been undertaken with a view to finding an insulating film composition made of polyethylene-2,6-naphthalate, that is not just electro-insulating

producing properties, but also satisfactory

N kQcontinuous /

physical properties with / long-term use under high temperatures has existed to produce, and it has been found that in the case of of polyethylene-2,6-naphthalate the stretching mode during biaxial stretching, the heating mode during the post-heat treatment and the post-heat treatment conditions, the physical properties of the obtained biaxially oriented and post-heat treated Have a very strong influence on the film, in particular the properties desired by an insulating film, and that known method of making biaxially stretched films useful for others Polymers, such as polyethylene terephthalate, were not applied directly to polyethylene-2,6-naphthalate can be applied.

For example, it was found that the. Refractive index (uz) in the direction of the biaxially stretched and post-heat treated film by the heating method, the stretch, wise and the post-heat treatment conditions can be greatly changed, with the result that the elongation of the film to the point of tearing when the same for a further post-heat treatment at 200 ° C

209835/1058

for a period of 200 hours, under conditions that allow free shrinkage of the film, is subjected to, is strongly influenced. It was found that only when the above mentioned Factors meet certain requirements, a biaxially oriented and post-heat treated Polyethylene 2,6-haphthalate insulating film obtained can be made due to the fact that it has excellent electro-insulating properties and

· Has

sufficient physical properties in order for ^ continuous /

long-term / high temperature use suitable to be ^ is extremely useful.

Accordingly, the primary purpose of the invention is to produce a biaxially oriented and post-heat treated film which has both sufficient physical properties to be used for long-term continuous / ⁱ
/ To be suitable for use under high temperatures

as well as excellent electro-insulating properties ten ^ has.

Other purposes. and advantages of the invention will be apparent from the following description.

The purposes of the invention can be achieved by a biaxially oriented and heat-treated polyethylene-2,6-naphthalate insulating film. which consists mainly of polyethylene-2,6-naphthalate, in which at least 90 mol% of the structural units Ethylene-2,6-naphthalate units are, and wherein the said film by biaxial insertion of an un-

"." \ HEAT initially gsbeaing Ungen / stretched film untrer J ~ unäHlurcBanschliessende

Post heat treatment under conditions that do not have free r, λ. If it is the film /

Allow the film to shrink, TTda-

characterized by that (i) the stretch ratio in the longitudinal or transverse direction within a range from 3 "to about ^ / lmTrelationship to the original

209835/1058

Chen width or length of the unstretched film is, on the condition that the stretch ratio in the transverse direction is at least 1 times, preferably Ϊ to 1.2 times, and most preferably 1-1.1 times the stretch ratio is in the longitudinal direction, (ii) that, when said biaxially oriented and wärmenachbehandelte film to a further heat treatment at 200 ⁰ C for a period of 200 hours under conditions that allow the free shrinkage of the film, subjected-we-d- that Elongation at break of the film obtained is not less than 10%>

preferably not less than 15%, most preferably 20% and (iii) that the refractive index in di-

kenrichtung (nz) of said biaxially oriented film and wärmenachbehandelten, measured at 20 ⁰ C with an Abbe refractometer using eineä beam of wavelength 589 m / U, within the following by the formula · ... .

1.499 -. (Na) = 1.520 preferably 1.500 = (nz) «1.515

defined range, and the intrinsic viscosity> (^) of the said film, measured at 35 ⁰ C in a mixed solvent of phenol and 2,4-, 6-tri chlorophenol, in the weight ratio of 6: 4-, within one Area covered by the

following formula ^ <,

0.4B ^ Cr ₁ ) ^ 0.70

defined range, on condition that the above (nz) and ( ¹ Q,) the following condition

meet: <

(nz) »0.3 X ty) + 1.361

As the polyethylene-2,6-naphthalate used as the base polymer in the invention, any poly-

209835/1051

merisate, in which at least 90 mol% of the structural units Ethylene-2,6-naphthalate units can be used. Accordingly, under that used here The expression "polyethylene-2,6-naphthalate" is not just one • Homopolymer of ethylene 2,6-naphthalate, but rather also a modified polyethylene-2,6-naphthalate with a

Proportion of less than 10 mol%, preferably less than 5 mole percent, of comonomer or modifier Understood. As it is likely that a film or sheet made from with more than 10 mol% comonomer or modified polyethylene-2,6-naphthalate modifier is deteriorated by the heat treatment, such a modified polymer not be used according to the invention.

In -general is polyethylene-2,6-naphthalate by reacting or naphthalene-2,6-dicarboxylic acid their functional derivatives with ethylene glycol or its functional derivatives in the presence of a Catalyst produced. The implementation conditions and production methods are known in the art, and are cited, for example, in the above-mentioned descriptions. When a comonomer / ^ or a modifier in an amount of less than 10 mol% before the end of the reaction to form polyethylene-2,6-naphthalate, is used, one or more suitable comonomers or modifiers are the Polymerization system is added, and then the reaction is through the formation of a copolyester or of a mixed polyester.

As such a comonomer of the modifying agent For example, compounds comprising a divalent ester-forming functional group can be used. Examples of such compounds are dicarboxylic acids, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, Terephthalic acid, naphthalene ^^ - dicarboxylic acid,

209335/1058

Succinic acid, diphenyl ether dicarboxylic acid and lower Alkyl esters of these dicarboxylic acids; Hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-hydroxyethoxybenzoic acid. and lower alkyl esters of these hydroxycarboxylic acids; and dihydric alcohols such as propylene glycol and trimethylene glycol. Polyethylene-2,6-naphthalate or its modified polymer can have terminal hydroxyl and / or carboxyl groups those by a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid and Methoxypolyalkylene glycol are capped. It is also possible with a very small one Amount of a polyfunctional compound such as glycerin and pentaerythritol modified to such an extent Polyethylene ^ jö-naphthalate that, linearity of the polymer is not significantly impaired to use.

It is possible to use such starting polyethylene-2,6-naphthalate various additives used in foil or film production. Examples such additives are matting agents such as titanium dioxide, stabilizers such as phosphoric acid, phosphorite acid and esters of these acids, as well as lubricants. , 'like finely divided silica (silicon dioxide) and finely divided China tone. . ,

It is desirable that the polyethylene-2,6-raphthalate used according to the invention have a basal molar Viscosity number (^) in the range from 0.50 to 0.80, since polymers with such an intrinsic viscosity (O can be processed well in films permit.

The intrinsic viscosity (* i) mentioned in the invention is determined by measurement in relation to

209835/1058

■ - ο -

on the polymer in a mixed solvent consisting of phenol and 2,4-, 6-trichlorophenol (phenol: 2,4,6-trichlorophenol weight ratio = 6: 4) is carried out at 35 ° C, where the unit is 100 cnrVg.

The refractive index mentioned in the invention (nz)

in the facility -, is the value that _%

is determined by the ^{measurement taking place at 20 °} C. with an Abbe refractometer by means of a beam of wavelength 589 (center of the D line).

An unstretched film _7, which is to be used for the production of a biaxially stretched and heat-treated film, can be produced using the methods customary in the art for film production; the starting polyethylene-2,6-naphthalate is usually dried to remove the water contained therein is then melted by an extruder or the like, extruded, cleared of debris or dirt, and then formed into a film. During this deformation process, the degree of polymerization of the polymer decreases, and the intrinsic viscosity (v?) Of the un-P stretched film fluctuates greatly depending on the drying and extrusion conditions of the starting polymer and other factors. In addition, the refractive index (nz) changes in the direction of the thickness of the biaxially oriented and post-heat treated film depending on the aforementioned change in the intrinsic viscosity (r ^) of the unstretched starting film and depending on the stretching and post-heat treatment conditions. The studies on the relationship between the

209835/1058

Changes in the intrinsic viscosity (τι)

\ Thick ^

and the index of refraction (nz) in the direction show that to achieve a biaxially stretched and heat-treated polyethylene-2,6-naphthalate film with sufficient physical properties to withstand long-term use under high temperatures to withstand and excellent electro-insulating properties, a specific, required relation between the intrinsic viscosity number

, s \ Picken and the refractive index (nz) must be set up in the direction of the film obtained.

More specifically, it was found that the refractive index (nz) in the ^x direction in the intended biaxially oriented and heat post-treated film made of polyethylene-2,6-naphthalate is within a range given by the following formula

1.499 = (nz) = 1.520 (preferably ■ 1,500 = (nz) ^ 1,515),

expressed range, and intrinsic viscosity (^) within one by the following formula

0.48 = O ₁ ) = 0.70

should lie within the expressed range, whereby the aforementioned (nz) and ( ¹ ^) should meet the following requirements:

(nz) = 0.5 X " (η) + 1.361.

It has also been shown that, in addition to the requirements set out above for the intrinsic viscosity (nz) and (^), the stretching ratio as well should meet certain requirements so that the film obtained has sufficient physical properties

^v continuous / „,,,,, th has to be suitable for deny lan extensive use under high temperatures. More precisely, it has

209835/1058

has shown that in the biaxially stretched film according to the invention the stretch ratio in the transverse or longitudinal direction should be within a range from about 3 to about 4 times, and the stretch ratio in the transverse direction should be at least 1 times, preferably ^{4 times} -Π, 2 times, ideally 1 - 1.1 times the stretching ratio in the longitudinal direction. As the stretch ratio in the transverse direction is less than 1 times the stretch ratio in the longitudinal direction, when the obtained eggim is used for a long period of time under high temperatures, the elongation at break in the transverse direction tends to be reduced very much. Whenever the stretch ratio in the transverse direction is higher than the preferred range given above, for example if the stretch ratio in the transverse direction is more than 1.3 times the stretch ratio in the longitudinal direction, the elongation at break in the longitudinal direction is often very greatly reduced. In order for the obtained egg to have sufficient physical properties to be suitable for long-term exposure to high temperature conditions as well as excellent electro-insulating properties, it is important that the stretch ratio in the longitudinal or transverse direction be within the above range, and that between the stretching ratios in the longitudinal and transverse directions. , the above relationship exists.

Biaxially stretched and post-heat treated polyethylene-2,6-naphthalate insulating films, which meet the requirements (i) and (iii) listed above, generally have an elongation at break of not less than 10% after another Heat treatment at 200 ° C for 200 hours under conditions conducive to shrinkage allow, have been subjected. To achieve the

209835/1058

- ΓΙ -

The purposes of the invention are biaxially stretched and post-heat treated Films with an elongation at break of not less than 10%, preferably not less than 15% »in particular not less than 20% after the further heat treatment mentioned above.

To achieve the biaxially oriented and post-heat treated polyethylene- ^ e-naphthalate insulating film composition of the invention, conditions such as the intrinsic viscosity ( η) of the unstretched film, the production conditions of the unstretched film, the stretching ratios in the biaxial

§ trek, the tenraeratur conditions in the biaxial _the_temperature restrictions of the ^ post-warming treatment ^ / Stretch ^ 'and the degree of restriction of the free

Shrinkage during post-heat treatment is freely selected and experimentally using the above Conditions (i), (ü) and (iii) are combined as criteria, although these conditions cannot be determined independently in a monistic manner. To better illustrate the invention Examples of embodiments are given below.

Scrap of polyethylene-2,6-naphthalate having an intrinsic viscosity (^) of, for example 0.50 to 0.80 can be several hours long with hot air heated to I70 - 200 is held ⁰ C, dried, and melted by a 290 - 300 C held extruder measured and extruded. The extrudate obtained is then formed into an unstretched film with the aid of conventional film forming devices. The unstretched film is about 3 to about 4 times the original length in the longitudinal direction at about 120 to about 160 ^° C., and in the transverse direction (width direction) about 3 to about 4 times

209835/1058

the original width at about. 115 "bit about 150 ⁰ C, preferably at about 135 to about 15O ⁰ C stretched to dans that draw ratio in transverse direction of at least 1 times the Streckvei · -.! Hältninooß longitudinally int" intestine is the biax da] stretched PoIie the to about 24-O allow heat treatment at about 170 ⁰ C under conditions not free shrinkage of the film, "generally subjected to this heat treatment is conducted under such schruropfungsbegrenzenden conditions that dei · Piim remains constant in the longitudinal direction, or the shrinkage of not W via 10? '> Goes out «

The biaxially oriented and heat-treated polyethylene-2,6-naphtha] at-lno] ierf iJinmateri al geinnas of the invention has excellent electrical properties, 2. «13, a high dielectric breakdown strength, a high specific surface resistance and a high specific volume resistance !, under temperatures as high as 155 ° or more O, and nearly constant dielectric properties at temperatures in the range from -60 ⁰ C bit -f 18ü ^(C, IU8;: ■ ground have the excellent films according to the invention ^ -: - mechanical properties,

such as tensile strength, Young-Iiodu], ultimate breaking strength, I? Eisi? ~ And impact resistance,. one

low thermal shrinkage without any »- Voj l. '-. hi ⁱ uni - /" n gofvc-n that ßeljrumj ^ fen are met, uj.d simple ^ fj clinetc; v / ärmebes the ZOm continui (-n use at 155 ° C is sufficient, ( V / heat resistance degree. F for insulating material! s according to the test proposed by the International Organization for ntfuid. ·>! ■ 'ii 7-oti.on - ISO, / They must be ordered to be sufficiently resistant to vpvfrchi eden insulating oil, .freon,

BATH ORIGINAL

.hi ο ö 3 ü / 1 υ s e

(refrigerator oils) ule4 which are used in refrigeration machines / 7 ~ organic solvents and plasticizers and, compared to Polyethylene terephthalate films, they do not become light hydrolyzed. Accordingly are. biaxially oriented and post-heat treated films according to the invention excellent insulation materials.

The films according to the invention can be used directly as insulating materials for various types of electrical and electronic machines used v / earth, a, b. Tape material for electrical and electronic Haschinen, as materials for slot insulation, for stage-phase insulation and as a construction material for capacitors. They can also be used with other insulating materials, such as cloth, paper, glass and other inorganic substances are laminated and in the form of layered products be used.

The following examples and comparative examples are intended to illustrate the invention.

The tensile mechanical properties used in the examples were used at 23 ° C in an environment of 65% relative humidity an Instron Tensile Tester determined by the following conditions:

Shape of the sample: strip (15 cm χ 1 cm)

Span ι 10 cm Pulling extent: 10 cm / min

Between the intrinsic molar viscosity number (I), which is mentioned in the invention, namely the intrinsic molar viscosity number (I) ₁₃ , measured at 35 ° C in a mixed solvent of phenol and 2,4,6-triethylorophosphate Weight ratio of 6 ι 4 _} imdjrler reason

2 0 3 «Ι 5/1 iJ 5 3 BAD ORlGlNM.

molar Viskosibäbszähl (l?) _-_ j measured at 35 Ci in o-chlorophenol, the following relationship is established;

0 |) _D. 1.008 χ (I ₁ ) + 0.0128

For games 1 to 9 and comparative examples 1 to 2

Polyäbhylen-2,6-naphthalab schnitzel with intrinsic viscosity 180 ⁰ O sufficiently long time (rp of 0.64 · on were) gebrockneb to gain by the specified in Table I. water content, and Ihei 290 - 300 ⁰ C melted. The melt was exbrudLerb, the residence time being set as indicated in Table I, and the Exbrudab was rapidly cooled and solidified on a casting drum at 50 ° C., and an unstretched film was obtained. a thickness of about 600, xx erhalben The unsaturated br-stretched film was subjected to the conditions listed in Table I, the obtained biaxially oriented film was wärmenachbehande1te and the stufenweiseri biaxial Sbreck- and heat treatment. beab-. sichtigterweise * verschlechterb in Enbspannungszustand at 200 ⁰ C in air, and the change in mechanical properties in the longitudinal direction is wurder'unbersuchb. The results are shown in Table HI.

BATH ORIGINAL

i Π χ »β; Π / ι rj S - ■>

received on.

01-54

U-

U Z

η Π Ol · Η IiUrH

dl:

to

U Φ -HP 'd M ο ο , Q C-?

ff U

O (0

ta

I rH4 ^ f ^ -H-H

fl> Ο <!) r-H

N CtS

• H ^ O Φ

O CQ

f-l pJ

O U Vi Φ

LO ο ω

ω ^ i U rl

to (H c ι

(ϋ η

O C

IA

γΗ

rH

O IA
CvJ (\ J

O H

O
OJ

f-l

O O

IA O
Oi IA

IA
tH

O fH

O O O O O (Tv ! A tA (\ J

(A.

tA OJ

ooo oooooo

CVJ <A id IA ID [S CQ

(M

_E HP;

CO co

ί i

rH fH fH CVJ IA CM O IA CVJ (M ir O O O O O O O O rH CU O O O O O O O O η

Hi to U

ft) φ G) C)

BATH ORIGINAL

9

b I Ί U 5 8

E.g,

Table I - Continuation of stretching conditions (condition i),

Post-heat treatment conditions

direction (L) ** Direction (B) * Stretching
ver
holds-
nis Stretch Tempe Time Conditions, (tempera
door Stretching
ver
holds-
nis T emp e
rature
( ⁰ C) behaves
nis (B) /
Stretch
behaves
nis (L)
* * * rature
( ⁰ C) (Sec) the no
free
Shrink
allow

1 155 O
CO 2 155 OO 5 140 cn CZJ 4th 155 cn OO 5 155 6th 150 7th 140 8th 140 9 140 Daily E.g. 1 155 See. E.g. 2 140

5.
5. 4th
7th 133
138 3.
4th 7th
O 1.
1. 1
07 255
240 · 10
15th 3%
Il in Br.
righs. ' It »R Mf 3. 5 ■ 155 3. 8th 1. 08 238 5 under Sjraaa-
tion Il 3- .5. 150 3- , 6 1. , 1 ■ 230 10 Il 3- ■ 5 150 3- ■ 7 1. .06 " 227 18th n 3. .6 155 3. .8th 1. , 06 220 10 • n 3 « *
VJl 125 3. .5- 1. .00 * 225 15th ti 2, .5 · . 155 3. .6 1, : 03 240 ' 15th 5 VJl 155 3 .6 1 .05 240 15th 5 .6 120 3 .5. O .97 25O 10 3 .5 125 3 .5 1 .00 240 15th

ίο too

° Notes; * Direction (B ") denotes the width direction, what for the following

¹⁰ tables also applies. , "

⁰⁰ ♦ * Direction (L) denotes the longitudinal direction, what for the following

£ J tables applies

■ v. ■ *** All values were determined by adding bridges from 0.005 and above to 0.01

^. rounded up . have been, and the rest have been neglected.

Table II

Ex.

Requirements for the films obtained

Requirements (ii)
to the received
Foils:

Elongation at break (%)
after further heat treatment 200 C,
200 hours with free
Shrinkage;

Breaking strength (kg / cm2) of the films obtained after further heat treatment 2090c, 200 hours, with free shrinkage;

Heat resistance test *

1- , 1,507 0.56 I.529 38 2 1,515 0.58 1,535 40 ro 3 1,519 0.60 0 .. COl. 541 51 09835/1 4th
5
6th 1,504
I.502
1,499- 0.55
O.54
0.53 1,526
I.523
I.52O 37
40
43 O
in
GO 7th
8th I.505
I.509 O.52
O.5O I.517
I.5II 27
30th 9
Cf.
Example 1
Forg.
Example 2 I.507
1,514
I.5O6 O.49
0.50
O.47 I.5O8
I.5II
I.502 22nd
3
4th

1540 1620 I59O I5IO 1580 1590 1480 I55O 1480

passed

It ti

failed

* According to the attempt proposed by the International Organization for Standardization

CO CT) CO

Examples 10-12 and Comparative Examples 5-5

Polyethylene 2,6-naphthalate chips having an intrinsic viscosity (»|) as shown in Table I were melted and extruded in the same manner as in Example 1, and an unstretched film having a thickness of about 600 ax was obtained. The unstretched film was biaxially stretched and post-heat treated under the conditions shown in Table 2Γ, and a biaxially stretched and post-heat treated film having an intrinsic viscosity (fQ and a refractive index (nz) in the thickness direction, both of which are shown in Table IEI) was obtained.

The physical properties of each film before and after the further heat treatment at 200 ⁰ C vährend 200 hours without precautions against the shrinking are shown in Table 4.

209835/1058

Table ill

Ex.

σ
cn
co

Stretching conditions sighting (L) | direction

temperature

( ⁰ C)

10

11

Cf.
Example 3

12th

Cf.
Example 4

Cf.
Example 5

140 150

140

I5O

140 155

Stretch ratio

temperature

( ⁰ C)

Stretch ratio

Heat treatment conditions

temperature

( ⁰ C)

Time

(Sec.)

Conditions that allow free shrinkage

Received pollen

(0) Cnz)

5-5 5.6

5.6 5-5

5-6 5.6

5o 145 5.8 1 * 5 5o 155 5o ΠΑ5 Z) 's

120

225
225 15th
10 UETcer
Sould
490 in
Br.rieht. 0.
0. 60
55 1.
1. .522 24-0 15th under
tension 0. ■ 53 1. .520 225 10 dd 0 ·. .70 514
, 520 25Ο 8th ti 0 * (u .522 245 15th It 0 • 50 1,520 ] __

CD CO CD CD U)

Table IV

O (O CO CO

Ex.

Before further heat treatment

Breaking strength ο (kg / cm *)

• Elongation at break

10 3 2300 11 2150 Cf.
Ex. M- 2150 12th 5 2350 Cf.
Ex. 2250 Cf.
Ex. 2100

70 55

50

73 70

51

After further heat treatment

Breaking strength ο (kg / cnr)

Elongation at break

( ⁰ Zo)

Heat resistance steat *

1680 1400

1200 175P 1250

1100

passed passed

failed

Pass / Fail

failed

* According to the T test proposed by the ISO

CD CO CD CD

2153963 -

Il

Examples 13-15 and Comparative Examples 6-7

An unstretched film made of an ethylene-2,6-naphthalate copolymer with an intrinsic viscosity (^) of 0.60, which is obtained by copolymerization using 97% 1% naphthalene-2,6-dicarboxylic acid as the dicarboxylic acid component and 3 mol% of terephthalic acid was prepared by simultaneously stretched in longitudinal and transverse direction (width direction) at / draw ratio of 3.5 in each direction at 130 ° C, and the stretched film was at 230 ⁰ C under tension wärmenachbehandelt (example 13) ·

An unstretched film of an ethylene-2,6-naphthalate copolymer with an intrinsic viscosity (n) of 0.56, which is obtained by copolymerization using 96.5 mol% of naphthalene-2,6-dicarboxylic acid as the dicarboxylic acid component and of 3 »5 mol% terephthalic acid was produced. The unstretched film was stretched in the longitudinal and transverse directions with a stretching ratio of 3-6 in each grading at 135 ° G, and post-heat treated at 235 ° C. under tension for 10 seconds (Example 14-).

A comparative product was produced in the same way as in Example 13, except that it was used as the starting polymer an ethylene-2,6-naphthalate copolymer obtained by copolymerization using of 85 mol% of naphthalene-2,6-dicarboxylic acid as the dicarboxylic acid component and 1% terephthalic acid was prepared from 15 Mo (comparative example 6).

As a further comparative product, a commercially available biaxially stretched and post-heat- treated polyethylene terephthalate film (Comparative Example 7) was used.

209835/1058

These films were subjected to further heat treatment at 200 ° C. for 200 or 400 hours under conditions which allowed free shrinkage. After this further heat treatment, the breaking strength, the breaking elongation and the dielectric breakdown were determined
resistance of the JOIien determined. The results are shown in Table V, where values for the film of Example 15? which was obtained from the polymer containing no terephthalate acid comonomer.

BATH ORIGINAL

209835 / 1U 5 8

CD
CO Ex. Tested foils I. .497 Table V (A) m 541 Stretch ratio (B) (BV (L) Fracture- Fracture d OO
co 1 .500 541 3.6 1.03 strengthens tion 5/1 1 .510 .529 (L) 3.5 1.00 (kg / cm ² ) (%) CD Often 1 .506 .529 3.5 3.6 1.00 2300 76 cn 0.68 1 3-5 3.6 1.00 2300. 75 X GO 15th 0.63 3.6 2210 73 13th 0.56 3.6 I7OO 80 14th 0.56 yergl.
exsp. 2210 126 before further heat treatment • Verg. Example 7 O, 3XCo3 + 1.361 1. 1. 1 1

CD CD Cx)

! Table V (B) '.
After further heat treatment

Ex. 6th 20O ⁰ C, 200
at free Hour
Shrink 53 7th Tensile strength
speed ρ voltage 56 * 15th 1680 55 * 13th 1840 * 7th 14th 1660 * VJl Cf.
Ex. '"8Ϊ0" * Cf.
Ex. 790

200 ⁰ C, 400 hrs free shrinkage

Breaking strength 'Bruchdehkeit _o planning

* The Behandlungs1 <emp £ temperature was 220 ⁰ C

μ ι? 1680 22 ·! 59O. 21st

to 13 1840 * 56 * 890 * 29 *

£ 14. 1660 * '53 * 770 * 23 *

O TUHOr ₁ . Λ "RIO" V 620 4

580 2

Examples 16-18 and comparative examples 8-10

Unstretched. Foil made from polyethylene-2,6-naphthalate with an intrinsic molar viscosity £ ^ J of 0.55 was carried out in the longitudinal and transverse directions under the conditions listed in Table VI using the method of biaxial stretching and post-heat treatment at 225 ° C for 10 seconds under tension, and a biaxially oriented film was obtained. The obtained film underwent thermal deterioration treatment in a state of relaxation in air at 200 ° C. The mechanical tensile strength properties of the film in the longitudinal and transverse directions were before and after the deterioration treatment certainly. The results are shown in Table VI.

209835/1058

Table VI

Example

Stretching conditions

Ii-direction

Stretch ratio
nis

B direction

temperature

C ⁰ O)

S " ¹⁶ 130 3. 5 155 OO U) 130 3. 2 130 —Λ 135 3- .7 138 "See. E.g-
8th 140 3- VJi 125 See. E.g. 135 3 .8th '135 See- E.g.
10 I3O 2 .8th 135

Stretch ratio
nis

• 1

B stretch ratio / L
stretch ratio

nis

Cnzl

Direction of mechanical tensile strength properties

Chterung before thermal Verschle

Fractional

3.8 1.08 1,504 L.

3.5 1.09 I.5O8 L

3.9 I.05 · I.502 L I.4 0.4 I.5IO L

3.6 0.95 1,504 L. 3.6 1.28 I.507 L.

2310
2400

2280
233O

2390
2410

2320
1980

2420
2380

2250
2420

75
70

83
75

74
73

74
115

71
80

95 '
72

After the thermal insurance

Break-proof, kt (kg / cm ^)

Elongation at break (%)

1460 I5OO

1480 I5IO

I52O I55O

1470 940

1480 1100

IO5O I53O

45 48

31 30

42 45

41 5

38 .8

9 • 33

CD CD Ca)

Claims (3)

Claims Jiaxially oriented and post-heat treated Insulating film made of polyethylene-2,6-naphthalate, consisting essentially of polyethylene-2,6-naphthalate, in which at least 90 mol% of the structural units are ethylene-2,6-naphthalate units are, with the film through biaxially stretching an unstretched film under J "and post-heat treatment conditions_", _Λ heating conditions /, as well as free shrinkage of the Film has been produced, characterized in that that the (i) draw ratio is either P in the width direction or in the length direction within a range of about ^3j to about 4 " g ' based on the unfolded width or length of the unstretched film, with the proviso that the stretching ratio in the width direction is at least 1 times the stretching ratio in the longitudinal direction, (ii) if the said biaxially oriented and post-heat treated film is part of a further heat treatment 200 ^° C. for 200 hours under conditions which allow free shrinkage of the film, the elongation at break of the resulting film is at least 10% and (Üi) k is the refractive index in the direction of thickness Cßz) of the biaxial oriented and post-heat treated film measured at 20 ⁰ C by means of the Abbe's refractometer using rays with a wavelength of 589 m / u within a range that passes through the following formula 1.499 = Cnz3 £ 1.520 is defined, and the intrinsic molar viscosity O] ") of the film, measured at 35 ⁰ C in a mixed solvent of phenol and 2,4,6-trichlorophenol at a weight ratio of 6: 4, within a range defined by the following formula 209835/1 058 0.48 ^ Op = 0.70 is defined, with the proviso that the above quantities of (nz ") and C ^ p clie the following condition «, fnz3 = 0.3 x € η) + 1 * 361 fulfill· 2. Biaxially oriented and thermally post-treated insulating film made of polyethylene-2,6-naphthalate according to claim 1, characterized in that the stretching ratio in the width direction is 1 to 1.2 times the stretching ratio in the longitudinal direction, the elongation at break after said further Heat treatment is at least 20%, and the refractive index in the thickness direction [p.z2 is within a range represented by the following formula 1500 = Qnz) = 1.515 is defined. 3. A process for the production of a biaxially oriented and thermally post-treated insulating film made of polyethylene-2,6-naphthalate according to claim 1, characterized in that an unstretched polyethylene-2,6-naphthalate _w film, which consists essentially of polyethylene-2, 6-naphthalate, wherein at least 90 Mo 1% of the structural units are ethylene-2,6-l-taphthalate units, at a draw ratio in either the width direction or the length direction in the range of about 3 to about 4 biaxially. stretched, the stretch ratio in the width direction of at least 1 times the stretch ratio is in the longitudinal direction, the stretching in the width direction at 115 to 150 ⁰ C and the stretching in the longitudinal direction 209835/1058 at 120-160 ⁰ C is performed, and then the biaxially stretched film to a heat treatment at 170 to 240 ⁰ C, under such conditions, subjecting at which held the film length constant and no shrinkage is permitted by above 10%, whereby a biaxially oriented and wärmenachbehandelter film is obtained in which, when this film is subjected to a further heat treatment at 200 ⁰ C for 200 hours under conditions that allow free shrinkage of the film, the elongation at break of the resulting film is at least 10% and the refractive index in the thickness direction ^nz C 0 of the biaxially orieni ^ ierten and wärmenachbehandelten film measured at 20 ⁰ C by means of an Abbe refractometer using rays of a wavelength of 589 m / 11 is within a range defined by the following formula 1.499 = (nzj * 1.520 and the intrinsic viscosity ( n) of the film as measured at 35 ° C in a mixed solvent of phenol and 2,4,6-trichlorophenol at a weight ratio of 6: 4 is within a range represented by the following formula 0.48 = C * p = 0.70 is defined, with the proviso that the above quantities (nz) and (nrp the following condition Cnz} = 0.3 x fcp + 1.361 . 209835/10 5 8