GB2192831A

GB2192831A - Polyphenylene sulfide film

Info

Publication number: GB2192831A
Application number: GB08711557A
Authority: GB
Inventors: Seiji Sakamoto; Hisashi Tsutsui
Original assignee: Diafoil Co Ltd
Current assignee: Diafoil Co Ltd
Priority date: 1986-07-25
Filing date: 1987-05-15
Publication date: 1988-01-27
Also published as: GB8816957D0; JPS6333427A; GB8711557D0; GB2205572A; DE3716180A1

Description

1

GB 2 192831A 1

SPECIFICATION Polyphenylene sulfide film

5 The present invention relates to a polyphenylene sulfide film.

More particularly, the present invention relates to an at least uniaxially oriented polyphenylene sulfide film comprising a polyphenylene sulphide resin containing from 2 to 30% by mole of m-phenylene sulfide recurring units, the polyphenylene sulfide resin comprising a blend of a polyphenylene sulfide (1) containing at least 15% by mole of m-phenylene sulfide recurring units and 10 a polyphenylene sulfide (2) containing at least 95% by mole of p-phenylene sulfide recurring units.

Polyethylene terephthalate films have been used as general-purpose industrial films, but in recent years, there has been a demand for, in particular, films further improved in heat resistance.

15 Aromatic polyamide films and polyimide films are known as typical examples of high heat-resistant films, but these films are very expensive since their starting materials are expensive and also because there is no alternative to the employment of a so-called casting method to form the film. On the other hand materials such as polycarbonate, polyester carbonate, polyarylate, polysulfone, polyether imide, and polyester sulfone, are known as materials to which the melt 20 film-forming method, which is advantageous in respect of film manufacturing cost, can be applied. These materials show relatively high heat resistance. These materials, however, are all amorphous and, therefore, films made of such materials are unsatisfactory in mechanical strength.

Thus, a film which is relatively low in cost and shows excellent heat resistance and mechanical 25 properties has been strongly required. Under these circumstances, attention has been focused on poly-p-phenylene sulfide film (hereinafter referred to as PPS film) as a film having a high possibility of meeting such requirements.

Regarding this PPS film, the film-forming conditions are disclosed in, for instance, Japanese Patent Publication Nos. 59-5099 (1984), 59-5100 (1984) (corresponding to U.S. Patent No. 30 4,286,018) and 59-5101 (1984), and the typical properties of this film are also known.

However, some technical difficulties are involved in the production of the oriented PPS film. For instance, because of the high crystallization rate of PPS homopolymers, the non-oriented film formed by extruding the homopolymers in sheet-form and cooling the thus obtain sheet tends to be partially crystallized and coarse spherulites are apt to form. Also, during the subsequent 35 stretching step, breaking of the film is apt to occur. It is thus difficult to obtain a stable PPS homopolymer film.

As a solution to such problems concerning the production of oriented PPS film, a method has been proposed in which a PPS copolymer composed of p-phenylene sulfide recurring units and other copolymerizable recurring units is used as starting resin. This method, however, is not 40 suitable for putting to practical use because usually the melting point of the polymer is greatly lowered and serious defects such as the deterioration of heat resistance appear with the reduced melting point of the copolymer.

In an aspect of the present invention, there is provided an at least uniaxially opented film comprising a polyphenylene sulfide resin containing 2 to 30% by mole of m-phepylene sulfide 45 recurring units, said polyphenylene sulfide resin being composed of a blend of polyphenylene sulfide (1) containing at least 15% by mole of m-phenylene sulfide recurring units and a polyphenylene sulfide (2) containing not at least 95% by mole of p-phenylene sulfide recurring units.

In the present invention, it is essential that the polyphenylene sulfide resin used for film-forming contains 2 to 30% by mole, preferably 5 to 20% by mole of m-phenylene sulfide 50 recurring units, and the resin composition satisfying such structural requirement is obtained by blending a polyphenylene sulfide (1) containing at least 15% by mole of m-phenylene sulfide recurring units and a polyphenylene sulfide (2) containing at least 95% by mole of P-phenylene sulfide recurring units. The polyphenylene sulfide (1) contains at least 15% by mole, preferably at least 40% by mole, more preferably at least 50% by mole of m-phenylene sulfide recurring units. 55 The residual recurring units are constituted by p-phenylene sulfide recurring units, but a small amount (not more than 5% by mole) of other copolymerizable recurring units such as

-0-s°2-Q-s-, -Q-o-Q-s-, -0-co-Q-s-. -0-0-s-,

60 CH3

-&s'. -COs-

65 and

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GB 2 192 831A 2

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may be present. When the content of m-phenylene sulfide recurring units in the polyphenylene sulfide (1) is less than 15% by mole, the melting point of the obtained film is markedly lowered and the film obtained is poor in heat resistance. The mode of linkage of m-phenylene sulfide recurring units may be random, block or graft, but block copolymers are especially preferred. 10 In the present invention, the most preferred form of polyphenylene sulfide (1) is the one containing not less than 50% by mole of m-phenylene sulfide recurring units combined in a blockwise fashion, the number of the blocks being not less than 20 on the average. It is also preferred to use m-phenylene sulfide homopolymers.

The polyphenylene sulfide (2) used in the present invention is one which is mainly composed 15 of p-phenylene sulfide recurring units, that is, the one containing at least 95% by mole,' preferably at least 98% by mole of p-phenylene sulfide recurring units, the residual recurring units being m-phenylene sulfide units and other copolymerizable recurring units. The most preferred form of polyphenylene sulfide (2) is poly-p-phenylene sulfide homopolymer.

In the present invention, the ratio of polyphenylene sulfide (1) to polyphenylene sulfide (2) to 20 be blended can not be stipulated absolutely as the ratio varies according to the composition of each resin but, for instance, in the case where an m-phenylene sulfide homopolymer is used as polyphenylene sulfide (1) and a p-phenylene sulfide homopolymer is used as polyphenylene sulfide (2), the (1)/(2) ratio is from 2/98 to 30/70.

Various known methods can be employed for the polymerization of the two types of polyphe-25 nylene sulfide used in the present invention, but the following method is preferred.

That it, an alkali metal sulfide, especially sodium sulfide and a corresponding dihalobenzene (m-dichlorobenzene and/or p-dichlorobenzene) and, if necessary, a halogen-substituted monomer capable of providing other recurring units are reacted in an amide polar solvent such as N-methylpyrrolidone in the presence of a polymerization auxiliary at a high-temperature under high-30 pressure conditions (U.S. Patent No. 3,354,129).

The present invention is characterised by the fact that a specified amount of m-phenylene sulfide recurring units is present in the polyphenylene sulfide resin used as a starting material in order to improve, principally, the film-forming properties, and a polyphenylene sulfide (1) containing at least 15% by mole of m-phenylene sulfide recurring units and a polyphenylene sulfide (2) 35 containing at least 95% by mole of p-phenylene sulfide recurring units are blended. The blends of the present invention we have studied show excellent effects that can never be obtained with the conventional copolymers.

According to the method of the present invention, the film-forming properties, that is, proces-sability during the preparation of the unstretched film and stretchability in the succeeding step 40 are improved because of the reduced crystallization rate of the polymer that is achieved by including the stipulated amount of m-phenylene sulfide recurring units. Further, since a high crystalization degree is maintained and the drop in melting point is minimized,

a film having excellent heat resistance and mechanical properties can be obtained.

In the present invention, use of the two types of polyphenylene sulfides (1) and (2) is an 45 essential requirement. The present inventors found that these two types of polyphenylene sulfides differing in melting point from each other can be mixed with each other relatively quickly, for instance, they can be mixed up within 5 minutes at 300°C and the obtained blend has a new melting point quite different from those of either polyphenylene sulfides. Further, this melting point is remarkably high in comparison with those of the known copolymers and is 50 preferable from the viewpoint of heat resistance.

For example, the melting point of the film made by using a polyphenylene sulfide obtained by random copolymerization and containing 12% m-phenylene sulfide recurring units is about 240°C and hence such film is defective in heat resistance. On the other hand the melting point of the film made by using as starting material a polyphenylene sulfide resin composed pf poly-m-55 phenylene sulfide and poly-p-phenylene sulfide in a ratio of 12 to 88 according to an embodiment pf the present invention is about 270°C, which indicates a striking improvement in terms of meting point of the film.

The'reason why such an effect is produced by the method of the present invention is not definitely known, but it is attributed to the fact that the blend presents a phenomenon quite 60 different from the copolymer due to the presence of m-phenylene sulfide recurriqg units in a specified content higher than a certain level, that is, due to uniform dispersion of block-like molecular chains in the poly-p-phenylene sulfide matrix.

In thje present invention, in order to maintain heat-resistance of the film, the two types of polyphenylene sulfides are generally blended in such a way that the obtained film will have a 65 melting point of 250 to 285°C, preferably 260 to 285°C.

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GB 2 192831A 3

Another advantage of the method of the present invention is that the polyphenylene sulfide films differing in content of m-phenylene sulfide recurring units, which have different properties can be obtained with ease. That is, it is possible to obtain the polyphenylene sulfide films with various contents of m-phenylene sulfide recurring units easily by merely changing the blending 5 ratio of polyphenylene sulfide (1) and (2).

In the present invention, the content of m-phenylene sulfide resin subjected to film-forming should be 2 to 30% by mole, preferably 5 to 20% by mole. If this content is less than 2% by mole, no improvement of film-forming properties tends to be provided, while if the content exceeds 30% by mole, both heat resistance and mechanical properties will be worsened. 10 In the present invention, it is possible to form a film by adding other polyphenylene sulfide(s) than the polyphenylene sulfides (1) and (2), but in this case, it is necessary that several essential requirements of the present invention, such as specified content of m-phenylene sulfide recurring units after blending, melting point, etc., be satisfied.

In the present invention, it is possible to include in the composition other polymer(s) such as 15 polyesters, polyamides, polyethylenes, polystyrenes, polycarbonates, polysulfones, polyether sul-fones, and polymides, and/or organic or inorganic compound(s) such as calcium terephthalate, calcium oxalate, glass fiber, carbon fiber, talc, kaolin, titanium oxide, silicon oxide, carbon black, and calcium carbonate, in the composition, both in an amount of not more than about 10% by weight based on the total amount of polyphenylene sulfides subjected to film-forming. Also, 20 additives such as antioxidant, heat stabilizer, lubricant, ultraviolet absorber, may be blended, if necessary.

A process for producing a film using the polyphenylene sulfide resin is described below.

The polyphenylene sulfide resin blended so as to contain 2 to 30% by mole of m-phenylene sulfide recurring units is supplied into a known melt extruder and heated therein to a temperature 25 above the melting point of the composition, so that it melts. The molten polyphenylene sulfide resin is extruded from a slit die onto a rotating cooling drum on which the resin is quickly chilled to a temperature below the glass transition temperature and is solidified, thereby obtaining a non-oriented sheet in a substantially amorphous state. In this process, in order to improve the flatness of the sheet, it is necessary to enhance adhesion between the sheet and the rotating 30 cooling drum. For this purpose, it is preferable to employ a so-called electrostatic cooling method. This is a method in which linear electrodes are provided on the upper surface of the sheet in the direction orthogonal to the flow of the sheet and a DC voltage of about 5 to 10KV is applied across the electrodes to give the electrostatic charges to the sheet, thereby enhancing adhesion of the sheet to the drum surface.

35 The thus obtained sheet is then uniaxially or biaxially stretched. Streching of the sheet can be effected by using, for example, a longitudinal stretching method which makes use of the difference in peripheral speed of the rolls. It is possible to employ other methods such as the tenter or the tubular method.

The film of the present invention, obtained from a blend of the two types of polyphenylene 40 sulfides of specific compositions, can be used as a uniaxially oriented film, but in view of uniformity of film properties, easiness of reducing the film thickness, film-forming efficiency, etc., the film of the present invention is more preferably used as a biaxially oriented film.

Stretching of the sheet is preferably conducted in the following way. The unstretched sheet is stretched from 2 to 5 times its original length in one direction by a tenter type stretching 45 machine at a temperature in the range of from 80 to 120°C, preferably 90 to 110°C. This stretching can be done either by a single-stage operation or in two or more stages. Then the sheet, if necessary, is further stretched 1.5 to 5 times in the direction orthogonal to the first stretching direction at a temperature in the range of from 80 to 150°C, preferably 90 to 140°C, to obtain a biaxially oriented film. Of course, the unstretched sheet may be stretched biaxially at 50 a temperature in the range of from 80 to 150°C so that the stretched sheet will have 3 to 30 times as large area as that of the unstretched sheet.

The thus obtained uniaxially or biaxially oriented film is preferably subjected to a heat treatment (heat-set) for improving, principally, the dimensional stability but if necessary, before such heat treatment, the oriented film may be again stretched in the machine direction and/or the 55 transversal direction to raise the orientation degree thereby enhancing mechanical strength.

Such uniaxially or biaxially oriented polyphenylene sulfide film is subjected to a heat treatment (heat-set) at a temperature between 180°C and melting point, preferably between 200°C and melting point, more preferably between 230°C and melting point, for a period of about 1 to 60 seconds under tension to increase the density and to improve dimensional stability, heat resis-60 tance, mechanical strength, etc. If necessary, the thus treated film may be subjected to relaxing treatment of not more than about 15% in both machine and transversal directions.

In this way, there can be obtained a uniaxially or biaxially oriented film according to the present invention. It is to be noted that the thus obtained stretched film, owing to the specificities of the starting materials, is remarkably improved in film-forming properties as compared with 65 the p-phenylene sulfide polymer film. Further, the film of the present invention has a high

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GB2 192 831A

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ultimate crystallization degree that can stand comparison with that obtainable with p-phenylene sulfide homopolymers and is also excellent in thermal and mechanical properties, and as a result is employed in various uses.

The oriented polyphenylene sulfide film of the present invention has a thickness of usually 1 to 5 1,000/im, preferably 1 to 100/zm, more preferably 1 to 50/im. Preferably, the film has a modulus of elasticity of not less than 300kg/mm2 in at least one direction, preferably not less than 300kg/mm2 in both machine and transversal directions, more preferably not less than 350kg/mm2 in both directions. It is also desirable that the ultimate crystallization degree of the film is not less than 20% more preferably 30 to 60%.

10 The polyphenylene sulfide film of the present invention obtained in the manner described above is excellent not only in thermal and mechanical properties but also in chemical stability, electrical properties, weather resistance and other properties, so that it can be favorably used as an electrical insulating film, packaging material, cover film for interior trims, base film for magnetic recording media, base film for photographic film, dielectric base film for capacitors, flexible 15 print substrate, or base film for thermo-sensitive transfer film.

Further, the polyphenylene sulfide film of the present invention is improved in film-forming properties, that is, it is its film-forming speed may be increased and the film-forming operated continuously, it is also excellent in heat resistance and mechanical properties.

The present invention willl be more precisely explained while referring to Examples as follows. 20 However, the present invention is not restricted to Examples under mentioned. From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and without departing from the scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

The method for determination and evaluation used in the present invention are as follows.

25

Thermal properties:

The melting point and glass transition temperature of each polymer were measured by using a differential scanning calorimeter manufactured by Perkin Elmer Co. In each case, a sample of about 10mg of polymer was subjected to measurements under a nitrogen atmosphere at a 30 heating rate of 10°C/min.

The heat shrinkage rate of the film was determined in the following way. about 10/xm thick heat-treated biaxially-oriented film was immersed in a silicone bath of 230°C for 30 seconds and the shrinkage rate was calculated from the ratio of the surface area of the film after immersion to that before immersion. The smaller measured value is better.

35

Film-forming properties:

They were evaluated from the following two aspects. In one aspect, they were evaluated by the end cutting properties of the unstretched sheet. The sample which had no notch formed along the length of not less than 100 meters continuously was marked by O, and the sample 40 which was notched 5 times or more and incapable of continuous formation was marked by X. The sample which showed the result intermediate between the above two samples was marked by A.

As another aspeqt of the evaluation, the continuity of film formation at the time of transversal stretching was observed. In all of Examples and Comparative Examples, the film forming rate at 45 the time of transversal stretching was adjusted to 5,000%/min, and the sample which suffered no break along the length of not less than 1,000 meters in the process continuously was marked by O, while the sample in which break occured 3 times or more and the continuity was hampered was marked by X.

50 Crystallization degree:

The crystallization degree was calculated by densitometry in which the density of the crystal phase and the amorphous phase was set at 1,430g/cm3 and 1,320g/cm3, respectively.

Modulus of elasticity:

55 Measured by using Tensilon (UTM—III) mfd. by TOYO BALDWIN CO., LTD. A 1cm wide and 10cm long piece was cut out from the film and its modulus of elasticity was measured at a tensile rate of 10cm/min with the chuck interval adjusted to 5cm.

Example 1 60 Synthesis of polyphenylene sulfides:

First, poly-m-phenylene sulfide was synthesized in the following way. 70 moles of [^-methyl-2-pyrroliflone, 1 mole of sodium sulfide nonahydrate(Na2S-9H20) and 0.5 moles of sodium acetate were supplied into an autoclave and the mixture was gradually heated to 210°C under stirring to remove water contained in the mixture.

65 Then the reaction system was cooled to 160°C, followed by the supply of 1.5 moles of m-

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GB 2 192831A 5

dichlorobenzene, and after sealing the autoclave, it was pressurized with nitrogen gas until the internal pressure reached 2.5kg/cm2. Then the mixture was heated to 270°C while controlling heat generation by polymerization and polymerized under stirring for 5 hours.

Then the reaction system was cooled and the pressure allowed to fall, and the reaction 5 mixture was poured into a large amount of water to obtain a flaky m-phenylene sulfide homopolymer (1). This polymer was washed repeatedly with distilled water and acetone to obtain a white granular product. Attempts were made to measure its melting point, but no definite value could be determined.

Next, poly-p-phenylene sulfide was synthesized by following the same operations as in the 10 preparation of the polymer (1) except that p-dichlorbenzene was used in place of m-dichloroben-zene. There was obtained a p-phenylene sulfide homopolymer (2) having a melting point of 279°C.

Production of polyphenylene sulfide film:

15 12 parts of the polyphenylene sulfide (1) and 88 parts of the polyphenylene sulfide (2) were blended, to which 0.4 parts of calcium carbonate having an average particle size of 1,0/zm was added for improving the handling quality, ie. slipping properties of the resulting film, and the mixture was melt-molded into an unstretched sheet using a T-die. That is, the mixed composition was sufficiently melted and kneaded at 300°C in an extruder, then extruded in the form of 20 a sheet from the nozzle having a width of 300mm and a lip interval of 1mm, and rapidly chilled and solidified on a rotating cooling drum having its surface temperature set at 40°C to obtain a substantially amorphous sheet having a thickness of 150/zm. The melting point and glass transition temperature of this sheet are shown in Table 1.

In this process, in order to make the thickness of the sheet more consistent, an electrostatic 25 cooling method was employed. That is, tungsten wires of 0.1mm in diameter were set on the under surface of the sheet in the direction orthogonal to the machine direction and a DC voltage of 7KV was applied across the wires to produce electrostatic charges on the sheet, thereby to contact tightly the sheet to the rotating cooling drum. 1

The obtained sheet had a greater thickness at the edge portion than at the central portion, so 30 that when it was cut at its both edges along a length of 2cm, no trouble occured and the next stretching operation could be accomplished without a hitch.

Stretching was conducted by first uniaxially stretching the sheet in the longitudinal direction (machine direction) by a longitudinal stretcher of a roll system comprising an infrared heater and nip rolls, and then further stretching the sheet in the transversal direction orthogonal to the 35 machine direction by a tenter type transversal stretcher, and then the biaxially stretched sheet was then subjected to a heat treatment (heat-set) at 250°C for 10 seconds.

The operating conditions used in the film-forming process and the results of the measurement are shown in Table 1.

40 Example 2

A biaxially oriented polyphenylene sulfide film was obtained in the same way as Example 1 except for the stretch ratio of 4.2 in the machine direction instead of the stretch ratio of 3.2.

Examples 3 and 4 45 Synthesis of polyphenylene sulfide:

By using m-chlorobenzene, p-dichlorobenzene and sodium sulfide nonahydrate(Na2S-9H20) as starting materials, there was obtained a polyphenylene sulfide (1) containing 60% by mole of m-phenylene sulfide recurring units in a block fashion.

The melting point of this polyphenylene sulfide (1) was 196°C.

50

Production of polyphenylene sulfide film:

The polyphenylene sulfide (1) and the p-phenylene sulfide homopolymer (2) obtained in Example 1 were blended so that the content of m-phenylene sulfide recurring units would become 5% by mole (Example 3) or 12% by mole (Example 4), and each blend was itreated 55 according to the process of Example 1 to obtain an unstretched sheet.

The: thus obtained unstretched sheets were subjected to the film forming operations under the conditions shown in Table 1 to obtain the approximately 10^m thick biaxially oriented polyphenylene, sulfide films.

60 Examples 5 and 6

Synthesis of polyphenylene sulfide:

By using m-dichlorobenzene, p-dichlorobenzene and sodium sulfide nonahydrate(Na2S-9H20) as starting materials, there was obtained a polyphenylene sulfide (1) containing 25% by mole of m-phenytene sulfide recurring units in a random fashion.

65 The-melting point of this polyphenylene sulfide (1) was 181°C.

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GB 2 192831A 6

Production of polyphenylene sulfide film-.

The polyphenylene sulfide (1) and the p-phenylene sulfide homopolymer (2) obtained in Example 1 were blended so that the content of m-phenylene sulfide recurring units would become 5% by mole (Example 5) or 12% by mole (Example 6), and each blend was treated 5 according to the process of Example 1 to obtain an unstretched sheet. 5

The thus obtained unstretched sheets were subjected to the film forming operations under the conditions shown in Table 1 to obtain the approximately IQum thick biaxially oriented polyphenylene sulfide films.

10 Comparative Example 1: 10

Film forming was carried out by using only a poly-p-phenylene sulfide, that is, the phenylene sulfide homopolymer (2) of Example 1 alone.

The film forming conditions and the results of the measurement are shown in Table 1.

15 Comparative Example 2: 15

By using m-dichlorobenzene, p-dichlorobenzene and sodium sulfide nonahydrate(Na2S-9H20) as starting materials, there was obtained a phenylene sulfide copolymer containing 10% by mole of m-phenylene sulfide recurring units in a random fashion, and by using this phenylene sulfide copolymer, the same film forming process as in Example 1 was carried out except for a change 20 of the stretching conditions to obtain a biaxially oriented polyphenylene sulfide film. 20

Example 7

The stretching properties of the films obtained according to the method of the present invention were compared with those of the films made by using poly-p-phenylene sulfide homo-25 polymers. 25

In Example 1, when the stretch ratio of the sheet in the machine direction was gradually raised, the sheet could be uniaxially stretched without break until the stretch ratio reached 4.6.

On the other hand, when the same test was conducted under the same stretching conditions as in Example 1 by using the polyphenylene sulfide (PPS) of Comparative Example 1, the sheet 30 had breaks when it was stretched 4.2 times the original length in the machine direction. 30

Table 1

Example or Comparative Example

Starting material

Non-

stretched

Stretched in machine direction

Stretched in transversal direction

Film forming properties and film properties

Film-forming properties

Crystallization degree

Heat-

shrink rate

Modulus of elasticity kg/mm*

exposition

Content of m-phenylene sulfide recurring units

Melting point

Glass transition tenp.

Stretching tenp.

Stretch ratio

Stretching tenp.

Stretch ratio

End cutting properties

Continuity of transversal stretching

Machine direction

Transversal direction

Exanple 1

Blend with m-phenylene sulfide hcmopolymer

12 moll

268°C

85°C

95°C

3.2

105°C

3.0

o

O

35%

-5.6%

370

360

H 2

II

12

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95

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3.0

o

O

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5.8

440

400

" 3

Blend with 60 moll m-phenylene sulfide block copolymer

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87

95

3.6

105

3.0

o

O

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5.3

400

380

H 4

If

12

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95

3.6

105

3.0

0

o

35

5.6

380

360

M 5

Blend with 25 mol% m-phenylene sulfide random copolymer

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85

95

3.6

105

3.0

o o

36

5.4

380

370

" 6

tl

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272

84

95

3.6

105

3.0

o o

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6.0

370

Corp. Example 1

Poly-p-phenylene sulfide haiD-polyner alone

0

279

89

100

3.6

110

3.0

A

X

38

5.2

390

370

tl

2

M-phenylene sulfide random copolymer alone

10

250

77

90

3.6

95

3.0

o

Melt-break at heat-treatment

-

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Claims

1. An at least uniaxially orientated film comprising a polyphenylene sulfide resin containing from 2 to 30% by mole of m-phenylene sulfide recurring units, the polyphenylene sulfide resin being composed of a blend of a polyphenylene sulfide (1) containing at least 15% by mole of m-

5 phenylene sulfide recurring units and a polyphenylene sulfide (2) containing at least 95% by mole of p-phenylene sulfide recurring units.

2. A film as claimed in claim 1, wherein the polyphenylene sulfide (1) comprises at least 15% by mole of m-phenylene sulfide recurring units, not more than 85% by mole of p-phenylene sulfide recurring units and not more than 5% by mole of other copolymerizable recurring units.

10 3. A film as claimed in claim 1 or claim 2, wherein the polyphenylene sulfide (1) comprises at least 40% by mole of m-phenylene sulfide recurring units and not more than 60% by mole of p-phenylene sulfide recurring units.

4. A film as claimed in claim 3 wherein the polyphenylene sulfide (1) comprises at least 50% by mole of m-phenylene sulfide recurring units and not more than 50% mole of p-phenylene

15 sulfide recurring units.

5. A film as claimed in claim 1, wherein the polyphenylene sulfide (1) is an m-phenylene sulfide homopolymer.

6. A film as claimed in any one of claims 1 to 4, wherein the polyphenylene sulfide (1) is a block, copolymer comprising m-phenylene sulfide recurring units and p-phenylene sulfide recurring

20 units.

7. A film as claimed in any one of the preceding claims, wherein the polyphenylene sulfide (2) comprises aat least 95% by mole of p-phenylene sulfide recurring units and not more than 5% by mole of copolymerizable units.

8. A film as claimed in claim 7, wherein the polyphenylene sulfide (2) contains at least 98%

25 by mole of p-phenylene sulfide recurring units.

9. A film as claimed in claim 7, wherein the polyphenylene sulfide (2) is a polymer comprising at least 95% by mole of p-phenylene sulfide recurring units and not more than 5% by mole of m-phenylene sulfide recurring units.

10. A film as claimed in claim 8, wherein the polyphenylene sulfide (2) is a p-phenylene

30 sulfide homopolymer. >

11. A film as claimed in any one of the preceding claims, wherein the content of m-phenylene sulfide recurring units in the polyphenylene sulfide resin is from 5 to 20% by mole.

12. A film as claimed in any one of the preceding claims, wherein the film thickness is from 1 to 1,000/mi.

35 13. A film as claimed in any one of the preceding claims, wherein the modulus of elasticity of the film in at lest one direction is not less than 300kg/mm2.

14. A film as claimed in any one of the preceding claims, wherein the ultimate crystallization degree of the film is at least by 20%.

15. A film as claimed in any one of the preceding claims, which is biaxially orientated.

40 16. A film as claimed in claim 1 and substantially as hereinbefore described yvith reference to any one of the examples.

17. A process for making a polyphenylene sulfide resin containing from 2 to 30% by mole of m-phenylene sulfide recurring units, the polyphenylene sulfide resin being composed of a blend of a polyphenylene sulfide (1) containing at least 15% by mole of m-phenylene sulfide recurring

45 units and a polyphenylene sulfide (2) containing at least 95% by mole of p-phenylene sulfide recurring units wherein the polyphenylene sulphides (1) and (2) are prepared by reacting an alkali metal sulfide with the relevant quantity of m- or p-dichlorobenzene and, optionally, a halogen substituted monomer capable of providing other recurring units in an amide polar solvent in the presence of a polymerisation catalyst at a high termperatue and pressure and then blending (1)

50 and (2) to produce the resin.

18. A resin prepared by a process as claimed in claim 17.

19. A film prepared from the resin of claim 18.

20. The use of a film as claimed in any one of claims 1 to 16 or claim 17 as an electrical insulating film, packaging material, cover film for interior trims, base film for magnetic recording

55 media, base film for photographic film, dielectric base film for capacitors, flexible print substrate, or base film for thermo-sensitive transfer film.

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Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.