GB2095166A

GB2095166A - Vinylidene fluoride polymer of high Young's modulus

Info

Publication number: GB2095166A
Application number: GB8204860A
Authority: GB
Original assignee: Kureha Corp
Current assignee: Kureha Corp
Priority date: 1981-03-02
Filing date: 1982-02-18
Publication date: 1982-09-29
Also published as: DE3207502A1; GB2095166B; FR2500839A1; FR2500839B1; DE3207502C2

Abstract

A vinylidene fluoride resin product has Young's modulus of 450 kg./mm<2> or more, an inherent viscosity ranging from 0.85 to 1.4 dl./g. and Huggin's constant of 0.45 or less. It may be made by spin drawing resin having an inherent viscosity and Huggins constant within the required range at a drawer ratio R such that <IMAGE> wherein napp is the apparent melt viscosity measured using an extrusion nozzle of 1 mm diameter and 3 mm thickness. A suitable drawer ratio may be 50:1 or more.

Description

SPECIFICATION Vinylidene fluoride resin product and preparation thereof BACKGROUND OF THE INVENTION FIELD OF TH INVENTION The present invention relates to a vinylidene fluoride resin product having high Young's modulus and a preparation thereof.

DESCRIPTION OF THE PRIOR ART: The conventional vinylidene fluoride resin filament had maximum Young's modulus ranging from 250-300 kg./mm2. The conventional vinylidene fluoride resin film had maximum Young's modulus ranging from 100--140 kg./mm2 as a nondrawn film and 180-260 kg./mm2 as a drawn film.

Such Young's modulus is not satisfactory for many usages. For example, when it is used as fishing thread, transmission of fishing is weak to cause low fishing rate. It has lower stiffness rather than the other filaments. When it is used as thread for electro musical instruments or a gut for a tennis racket, a repulsive coefficient is low whereby characteristic cannot be attained satisfactorily.

When vinylidene fluoride resin is used as window glass or sun room in view of properties transmitting lights in a wavelength region of 2800-3300 A as Dorno Ray, ultra-violet rays which is shielded by a normal glass are permeated to be advantageous for health. The conventional vinylidene fluoride resin film had low Young's modulus whereby deformation or sagging is caused by applying slight pressure. Thus, it is necessary to take care in handling.

Moreover, vinylidene fluoride has excellent weathering resistance. If vinylidene fluoride resin having high Young's modulus is obtained, a large demand can be expected in various outdoor usages such as construction materials, industrial material and transportation materials. Furthermore. vinylidene fluoride resin does not substantially deteriorate in strength in water. If vinylidene fluoride resin having high Young's modulus is obtained, it is expected to contribute to developments in the sea.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vinylidene fluoride resin product having high Youngs modulus and a preparation thereof.

It is another object of the present invention to provide a vinylidene fluoride resin product having a low elongation and high tensile strength in an application of large stress which is superior to the conventional fluoride resin having maximum ultimate elongation of 20%.

The foregoing and other objects of the present invention has been attained by providing a vinylidene fluoride resin product having Young's modulus of 450 kg./mm2 or more; and a process for producing a vinylidene fluoride resin filament which comprises melt-extruding a vinylidene fluoride resin having an inherent viscosity ranging from 0.85 to 1.4 dl/g. and a Huggin's constant of 0.45 or less; and drafting said resin to orientate it under a condition of melt-extrusion to give a draft ratio of R 77app 540 5.4x104 wherein w7app represents an apparent melt viscosity measured by extruding by a-melt indexer through a nozzle having a diameter of 1 mm and a thickness of 3 mm, and R represents a draft ratio; and cooling the extruded resin; and a process for producing a vinylidene fluoride resin film which comprises meltextruding a vinylidene fluoride resin having an inherent viscosity ranging from 0.85 to 1.4 dl./g. and a Huggins' constant of 0.45 or less; and drafting said resin at a draft ratio of 50 or more contacting said resin with a first roll with substantial stress release; and cooling said drafted resin.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a vertically sectional view of an apparatus used in the process of Examples 1 to 6 wherein the reference 1 designates a sample; 2 designates a heater; 3 designates a nozzle; 4,4l,41r respectively designate guide rolls; 5 designates a pinch roll; and 6 designates a plunger.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In view of high Young's modulus of polyester fiber of polypropylene fiber obtained by quenching rapidly a molten polymer result a crystallization in orientation under high share strain, it has been studied to obtain a polyvinylidene fluoride fiber having high Young's modulus. Thus, it has been found that high Young's modulus can be given only under a special condition in the case of a polyvinylidene fluoride fiber to be different from those of the polyester fibers and the polyolefin fibers. It is found that such specific condition is depending upon a melt viscosity and a branched degree.

It has not been succeeded to obtain a film having high Young's modulus by the same improvemen as those of the filament in the case of polyvinylidene fluoride as well as polyesters and polyolefins.

In such technological level, various studies have been carried out. As a result, it has been found that the desired film is obtained only by drafting a molten resin at a position slightly departed from an outlet of a die after an extrusion to result a substantial elongation.

The present invention will be illustrated in detail.

Vinylidene fluoride resin used in the present invention has an inherent viscosity 0.85 to 1.4 di./g.

preferably 0.9 to 1.3 dl./g. especially 1.0 to 1.2 dl./g. When the inherent viscosity is higher than the range, a fabricating process is not easy and a thermal decomposition is easily caused in a fabricating process at high temperature whereas it is lower than the range, high draft ratio is not substantially attained and a mechanical strength is lowered because of unevenness of diameter in the drafting.

The inherent viscosity z1inh. is measured as in a solvent of dimethyl acetamide at a concentration of 0.4 g./dl. at 300C.

The vinylidene fluoride resin used in the present invention has Huggins' constant of 0.45 or less.

When Huggins' constant is more than 0.45, high draft ratio is not attained in the drafting. Huggins' constant is measured in a solvent of dimethyl acetamide at 300 C. Huggins' constant is preferably 0.4 or less and especially 0.35 or less.

The vinylidene fluoride resins used in the present invention means vinylidene fluoride homopolymer or vinylidene fluoride copolymer having vinylidene fluoride component of 90 mol.% or more preferably 95 mol.% or more especially 97 mol.% or more or a resin composition which contains the homopolymer or the copolymer at a content of 70 wt.% or more preferably 90 wt.% or more.

In order to prepare a filament, the vinylidene fluoride resin is melt-extruded and drafted to result orientation under a molten condition and cooled it. In order to result the orientation under the molten condition in the drafting, a ratio of a taking-up speed to an extruding speed as a draft ratio is given in the relation of an apparent melt viscosity, as follows: R rjapp + 540 5 x 104 preferably R 77app + > 1.1 540 5.4 x 104 especially R t1app + > 1.2 540 5.4x104 wherein R represents a draft ratio and w1app represents an apparent melt viscosity measured by extruding from a melt indexer through a nozzle having a diameter of 1 mm and a thickness of 3 mm.

High Young's modulus is given by the selection of the draft ratio.

In order to prepare a film, the vinylidene fluoride resin is melt-extruded and drafted to result orientation under a molten condition and cooled.

In order to result the orientation under the molten condition in the drafting, a ratio of a taking-up speed to an extruding speed as a draft ratio is 50 or more preferably 100 or more. It is preferable to give the relation of the draft ratio to an apparent melt viscosity as described above as well as the draft ratio.

When the apparent melt viscosity is low, the draft ratio is relatively higher whereas when the apparent melt viscosity is high, the draft ratio is relatively lower. In usual cases, the orientation is higher to give higher Young's modulus by increasing the draft ratio.

In the case of the film, the draft ratio is selected from the aforementioned range, and the drafting position for substantial elongation is only a position departed slightly from the outlet of a die. The drafting position for substantial elongation means the position for substantially reducing a diameter, a thickness our a depth of the molten resin.

In the case of a filament, a distance between the outlet of the die and the position for substantial elongation is slightly changed depending upon an extrusion temperature, an extrusion speed, etc. Thus, the elongation is substantially completed without a special manner near 50 cm from the outlet of the die under a normal condition. The filament is easily fabricated among various fabricated product On the other hand, in the case of a film, as it has not known to give high Young's modulus for polypropylene or polyethyleneterephthalate, it is not easy to obtain a film having high Young's modulus. It has been found that the object product having high Young's modulus is obtained by maintaining a distance between an outlet of a die and a roll contacting firstly the resin to 10 cm or shorter preferably 5 cm or shorter and maintaining the surface temperature of the roll to a low temperature so as to define the position for substantial elongation in front of the roll in the drafting and crystallizing it by the roll.

The position for substantial elongation in the drafting is forcibly defined or naturally defined depending upon the resulting product, because a stress releasing is easily given or not depending upon a shape of the product. In the case of a film, the stress releasing in the transversal direction is easily given rather than that of the film in the vertical direction whereby it is necessary to perform the drafting in the defined position from the die as described.

After drafting under the aforementioned condition in a molten state, the product is cooled so as to prevent the stress releasing. The rolls for the preparation of the film are effective for controlling the configuration of the elongated part and forcible cooling. The cooling manner can be a spontaneouscooling as well as a forcible cooling. The forcible cooling can be carried out by the conventional means.

For example, a cooling roll is used or a coolant is used. The cooling temperature is lower than the maximum crystallization velocity of the resin, preferably lower than 500C from the temperature for the maximum crystallization velocity. For example, vinylidene fluoride homopolymer has the temperature for the maximum crystallization velocity of about 1 300C, whereby it is preferable to cool it at 800C or lower.

In the process of the present invention, only the vinylidene fluoride resin can be extruded to produce a simple product and vinylidene fluoride resin can be coextruded with another plastic resin to produce a laminated product.

In the process of the present invention, the draft ratio is remarkably high such as several tens to several hundreds. This is remarkably higher than the draft ratio for example, several in the conventional process for melt-extruding the resin and crystallizing and then drafting whereby the productivity is remarkably improved.

In the conventional drafting process, the crystallizing step and the drafting step are separated.

Moreover,'in the conventional process, a heat-treating step is needed after the drafting step because of serious heat shrinkage. On the other hand, in the present invention, the crystallizing step and the drafting step are substantially carried out as one step and the resulting-product has low heat shrinkage and any heat-treating step is not needed and the steps for the production are remarkably decreased.

In accordance with the process of the present invention, a product having-Young's modulus of 450 kg./mm2 or more in the drafting direction is obtained. The product having Young's modulus of 600 kg./mm2 or more especially 700 kg./mm2 or more is obtained by increasing the draft ratio. The resulting product has a-crystalline form. The product obtained at such high draft ratio cannot be drawn in the case of polypropylene or polyethylenetetraphthalate whereas the product obtained at such high draft ratio can be cold-drawn in the case of the vinylidene fluoride resin. The resulting product has mainly ss- crystalline form and has higher Young's modulus.

For example, in the case of a filament, it is possible to obtain a filament having Young's modulus of 800 kg./mm2 or more. It is also possible to obtain a filament having Young's modulus of 1000 kg./mm2 or more, further 1200 kg./mm2 or more. The Young's modulus means an initial modulus measured by stretching a sample having a length of 100 mm at a velocity of 10 mm./min. at 230C by a tensilone tester.

The film obtained by.the process of the present invention has lower Young's modulus in the direction perpendicular to the drafting direction rather than the Young's modulus in the drafting direction. When two sheets of the film are plied so as to cross the drafting directions, a plied film having high Young's modulus in both the vertical and traverse directions can be obtained. Only one sheet of the film can be used in a usage for applying stress only one direction.

The present invention will be illustrated by certain examples and references which are provided for purposes of illustration only and are not intended to be limiting the invention.

EXAMPLES 1 TO 6 AND REFERENCES 1 TO 6 In Examples 1 to 6 and References 3 to 6, each vinylidene fluoride homopolymer having 71ins. of 1.1 dl./g. and Huggins' constant of 0.303 in a form of pellets was extruded through a nozzle having a diameter of 1 mm and a thickness of 3 mm at an extruding rate of 0.63 g./min. by a melt indexer (Toyo Seiki K.K.) (Figure 1 shows a diagram). After the extrusion, each extruded polymer was spontaneously cooled in an atmosphere at 250C through a guide roll (4) set in a distance just below about 80 cm from the nozzle (3) and was taken up by a take-up roll (5) having a diameter of 10 cm. The surface temperature of the take-up roll was 250C.In the apparatus, each polymer was extruded at a melt temperature of 2000C, 220 C, 240"C or 260"C at various draft ratios. The properties of the filaments obtained by the process; each tensile strength and each ultimate elongation measured by stretching each sample having 100 mm at 230C at a velocity of 100 mm./min. by a tensilone tester (Toyo Balling K.K.) and each initial Young's modulus obtained from a stress-strain curve measured by stretching each sample having 100 mm at a velocity of 10 mm./min. are shown in Table 1.

In Reference 1, a filament made of the same polymer used in Example 1 was drawn at a drawing ratio of 6 at 1 600C and heat-treated at 1 620C under tension.

In Reference 2, a filament made of the same polymer was drawn at a drawing ratio of 4.5 at 1 000C. The results are also shown in Table 1.

Table 1

1 2 3 4 5 6 Reference 1 2 3 4 5 6 Extrusion temperature () - - 200 200 200 240 Melt viscosity (x10-4 poise) 3.9 3.9 3.9 2.6 Draft ratio or drawing ratio (R3 6* 4.5* 3 14 75 140 R 77app + + 0.73 0.75 0.86 0.74 5.4x104 Young's modulus (kg./mm2) 280 265 120 160 170 190 Tensile strength (kg./mm2) 80 55 6 8 12 13 Ultimate elongation (%) 28 40 480 400 270 180 Table 1'

Example 1 2 3 4 5 6 Extrusion temperature ( C) 220 240 240 260 280 290 Melt viscosity (x10 poise) 3.2 2.6 2.6 1.9 1.6 1.5 Draft ratio or drawing ratio (R*) 220 350 390 450 820 860 R #app + 1.00 1.03 1.20 1.19 1.81 1.87 540 5.4x104 Young modulus (kg./mm 480 570 610 650 820 850 Tensile strength (kg./mm2) 47 63 80 85 90 93 Ultimate elongation (%) 70 45 40 35 28 25 REFERENCE 7 Vinylidene fluoride homopolymer having rlinh of 1.1 8 dl./g. and Huggins's constant of 0.70 obtained by an emulsion polymerization at 110 C in a form of pellets was melt-spun at high draft ratio as that of Example 1. Even though the melt-spining was carried out at a melt temperature of 3100C, the maximum draft ratio was about 1 5. When the melt temperature was further raised, the melt-spining could not be performed by foaming caused by decomposition of the polymer.

REFERENCE 8 Vinylidene fluoride homopolymer having rlinh of 1.62 dl./g. and Huggins' constant of 0.31 obtained by a suspension polymerization at 250C was melt-spun at high draft ratio as that of Example 1. Even though the melt-spining was carried out at a melt temperature of 31 O0C. the maximum draft ratio was about 1 0. When the draft ratio was further increased, the filament was out. The melt-spining at high draft ratio could not performed.

EXAMPLE 7 The filament obtained in Example 6 was drawn at a ratio of 20% in a silicone bath at 1 500 C. The resulting filament had Young's modulus of 1460 kg./mm2 and a tensile strength of 112 kg./mm2.

EXAMPLE 8 In the apparatus used in Example 1, vinylidene fluoride homopolymer having qinh of 1.25 di./g.

and Huggins' constant of 0.31 was extruded at a melt temperature of 2800C at an extruding rate of 0.63 g./min. through a nozzle having a diameter of 1 mm and a thickness of 3 mm. The condition for the take-up after the extrusion was the same as that of Example 1 except varying a draft ratio R=620, the resulting filament had Young's modulus of 780 kg./mm2.

EXAMPLE 9 AND REFERENCES 9 AND 10 Vinylidene fluoride homopolymer having 11ins of 1.0 dl./g. and Huggins' constant of 0.324 in a form of pellets was extruded at a resin temperature of 2200C and an extruding rate of 4.5 g./min. by a smaller extruder equipped with a rectangular die having a width of 25.4 mm and a thickness of 0.5 mm.

The extruded film was directly taken up by a pair of pinch rolls as rubber rolls. The pinch rolls were placed near the die in a distance of 3 cm between the end of the die and the pinched part of the pinch rolls. A cool air was fed by a hair drier set between the end of the die and the pinch rolls.

As Reference 9, a film was taken up by the process of Example 9 except varying the distance between the end of the die and the pinch rolls to 50 cm.

The physical properties of the resulting films are shown in Table 2.

As Reference 10 a film made of the same resin having a thickness of 1 OOju was uniaxially drawn at 1 000C at a drawing ratio of 4. The physical properties are also shown. The Young's modulus and the tensile strength in the direction of the drafting or the drawing are shown in Table 2.

Table 2

Example or Reference Exp. 9 Ref. 9 Ref. 10 Shape of film obtained through a die having a size of 25.4 mm x 0.5 mm Thickness (tL) 7 53 Width (mm) 14.0 2.8 Draft ratio or Drawing ratio (R*) 130 130 4* Young's modulus (kg/mm2) 460 180 220 Tensile stiength (kgZmm2? 90 45 85 Heat shrinkage at 160 C (O/o) 4 3 37 REFERENCE 11 Vinylidene fluoride hompolymer having 77inh of 1.1 8 dl./g. and Huggins' constant of 0.70 obtained by a polymerization at 1 00C in a form of pellets was extruded at a die temperature of 2500C in a distance of 10 mm between the die and the rolls, at high draft ratio so as to produce a film. However, it could not be taken up a film because of breaks of the film.

The die temperature was further raised to 3000C, the breaks of the film were found. It was substantially difficult to take-up at high draft ratio. The maximum draft ratio for possible take-up was only 5.

REFERENCE 1 2 Vinylidene fluoride hompolymer having qinh of 1.62 dl./g. and Huggins' constant of 0.31 obtained by a suspension polymerization at 250C was extruded by the process of Example 9 at high draft ratio so as to produce a film. However, it could not be taken up film because of breaks of the film.

The die temperature was further raised to 3100C, the breaks of film were found. It was substantially difficult to take-up at high draft ratio. The maximum draft ratio for possible take-up was only 4.

At higher die temperature, the resin was decomposed to form foaming. It is difficult to extrude the resin at higher temperature.

EXAMPLE 10 Vinyl;dene fluoride hompolymer having 11inh of 1.20 ditg. and Huggins' constant of 0.32 was extruded by the extruder of Example 9 at a resin temperature of 2800C at an extruding rate of 4.5 g./min. and drafted at high draft ratio of Example 9 of 120 and taken up to produce a film having Young's modulus of 510 kg./mm2.

As it is understood from the examples, the products of the present invention have remarkably high Young's modulus rather than those of the conventional vinylidene fluoride resin products.

When a cold drawing is performed after drafting at a draft ratio of 500 or more in the case of a filament and a draft ratio of 100 or more in the case of a film, a product having an ultimate elongation of 15% or less and a tensile strength of 90 kg./mm2 or more can be obtained.

Claims

1. A vinylidene fluoride resin product having Young's modulus of 450 kgtmm2 or more, an inherent viscosity ranging from 0.85 to 1.4 dl./g. and Huggins' constant of 0.45 or less.

2. The vinylidene fluoride resin product according to Claim 1 which has Young's modulus of 600 kg./mm2 or more.

3. The vinylidene fluoride resin product according to Claim 1 which has Young's modulus of 800 kg./m m2.

4. The vinylidene fluoride resin product according to Claim 1,2 or 3 which has an ultimate elongation of 15% or less and a tensile strength of 90 kg./mm2 or more.

5. The vinylidene fluoride resin product according to Claim 4 which has an ultimate elongation of 10%orless.

6. The vinylidene fluoride resin product according to Claim 4 or 5 which has a tensile strength of 95 kg./mm2 or more.

7. The vinylidene fluoride resin product according to Claim 4, 5 or 6 which has a tensile strength of 100 kg./mm2.

8. The vinylidene fluoride resin product according to Claim 1, 2, 3, 4, 5, 6 or 7 which is in a form of a filament.

9. The vinylidene fluoride resin product according to Claim 1,2, 3, 4, 5, 6 or 7 which is in a form of film.

10. A process for producing a vinylidene fluoride resin filament which comprises melt-extruding a vinylidene fluoride resin having an inherent viscosity ranging from 0.85 to 1.4 dl./g. and a Huggins' constant of 0.45 or less and drafting said resin to orientate it under a condition of melt-extrusion to give a draft ratio of R 77app + > 1 540 5.4x1O4 wherein 77app represents an apparent melt viscosity measured by extruding by a melt indexer through a nozzle having a diameter of 1 mm and a thickness of 3 mm; and R represents a draft ratio; and cooling the extruded resin.

11. The process according to Claim 10 wherein said draft ratio R is R 71app + > 1.1 540 5.4x104

12. The process according to Claim 10 wherein said draft ratio R is R 7app + 540 5.4x104

1 3. The process according to Claim 10, 11 or 12 wherein said extruded resin is drafted followed by a cold drawing.

14. The process according to Claim 13 wherein a draft ratio is 500 or more.

15. The process according to Claim 10, 11, 12, 12 or 14 wherein said resin has an inherent viscosity ranging from 0.9 to 1.3 dl./g.

1 6. The process according to Claim 1 5 wherein said resin has an inherent viscosity ranging from 1.0 to 1.2 dl/g.

1 7. A process for producing a vinylidene fluoride resin film which comprises melt-extruding a vinylidene fluoride resin having an inherent viscosity ranging from 0.85 to 1.4 dl./g. and a Huggins' constant of 0.45 or less; and drafting said resin at a draft ratio of 50 or more; contacting said resin with a first roll without substantial stress release; and cooling said drafted resin.

18. The process according to Claim 17 wherein said extruded resin contacts with a first roll in a distance of 10 cm or shorter from a nozzle.

19. The process according to Claim 1 7 or 18 wherein said draft ratio is 100 or more.

20. The process according to Claim 17, 18 or 1 9 wherein said resin is drafted followed by a cold drawing.

21. The process according to Claim 1 7, 1 8, 19 or 20 wherein said resin has an inherent viscosity ranging from 0.9 to 1.3 dl./g.

22. The process according to Claim 21 wherein said resin has an inherent viscosity ranging from 1.0 to 1.2 dl./g.

23. A vinylidene fluoride resin product according to Claim 1, substantially as herein described with reference to any one of the Examples.

24. A process according to Claim 10 substantially as herein described with reference to any one of the Examples.

25. A process according to Claim 1 7 substantially as herein described with reference to any one of the Examples.