Process for produce a readily slidable film

• US 5,476,899 A
• Filed: 12/15/1993
• Issued: 12/19/1995
• Est. Priority Date: 09/14/1989
• Status: Expired due to Fees

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: Idemitsu Kosan Company Limited
• Inventors: Ohki, Yuichi, Takama, Hideyuki, Funaki, Keisuke
• Primary Examiner(s): Michl, Paul R.
• Assistant Examiner(s): Guarriello, John J.
• Application Number:
  US08/168,273
• Time in Patent Office: 734 Days
• Field of Search: 524/423, 524/413, 524/427, 524/432, 524/433, 524/436, 524/437, 524/442, 524/451, 524/496, 524/497, 524/577, 264/167, 264/170, 264/171, 526/347.2
• US Class Current: 524/577
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: C08J 2325/06 Polystyrene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08K 3/013 Fillers, pigments or reinforcing additives
• CPC Class Codes: C08L 25/06 Polystyrene

Abstract

A process for the production readily slidable films which are stretched films. The process comprises (a) uniaxially stretching in a machine direction a pre-molded product comprising a composition of a styrene polymer having a high degree of syndiotactic configuration compounded with 0.001 to 1% by weight of inorganic filler particles with an average particle diameter of 0.01 to 3 μm, or simultaneously, biaxially stretching the premolded product in the machine direction and the transverse direction and (b) subsequently uniaxially restretching the premolded product in the traverse direction or simultaneously, biaxially restretching the premolded product in the machine direction and the transverse to produce a film having a surface roughness Ra of 0.005 to 0.03 μm, and a static friction coefficient μs of 0.3 to 1.0. The readily slidable films have high heat resistance, mechanical strength and electrical insulating properties and are excellent in sliding properties and smoothness.

Claims

1. A process for production of a readily slidable stretched syndiotactic polystyrene film comprising

stretching and then restretching in a plurality of stages a styrene polymer having a high degree of syndiotactic configuration compounded with 0.001 to 1% by weight of inorganic fine particles having an average particle diameter of 0.01 to 3 μ

m, so that said film has a surface roughness, Ra, of 0.005 to 3 μ

m and has a static friction coefficient, μ

s, of 0.03 to 1.0, said stretching and restretching being a mode selected from the group consisting of

(i) first stage;

uniaxial stretching in the machine direction in a stretching ratio of 1.2 to 5 and at a temperature from a glass transition temperature to a cool crystallization temperature to obtain an absolute value of birefringence of said film of 3×

10^-3 to 70×

10^-3, second stage;

uniaxial restretching in the transverse direction at a stretching ratio of 1.5 to 5 and at a temperature of 5°

C. higher than a glass transition temperature to 30°

C. lower than a melting point, third stage;

uniaxial restretching in the machine direction; and

(ii) first stage;

biaxial stretching in the machine direction at a stretching ratio of 1.2 to 5 and in the transverse direction at a stretching ratio of 1.2 to 5 and at a temperature from a glass transition temperature to a cool crystallization temperature, second stage;

uniaxial restretching in the machine direction.

2. The process according to claim 1, wherein the styrene polymer has a high degree of syndiotactic configuration or a composition thereof has a density of not more than 1.07 g/cm³ and a crystallinity of 5 to 30%.

3. The process according to claim 1, wherein the styrene polymer has a high degree of syndiotactic configuration is obtained by heat-melting the styrene polymer having a syndiotactic configuration or a composition thereof at a temperature higher than a melting point of said styrene polymer and lower than a decomposition point+50°

C., and cooling.

4. The process according to claim 1, wherein the total stretching ratio in the machine direction of the resulting film is 2.5 to 12.

5. The process according to claim 1, wherein the film obtained is further heat-treated.

6. The process according to claim 1, which further comprises carrying out a chemical and/or physical treatment to obtain a surface tension of the film partly or completely to not less than 35 dyne/cm.

10. The process according to claim 1, wherein the styrene polymer is a syndiotactic polystyrene having a residual aluminum content of not more than 3,000 ppm, a residual titanium content of not more than 10 ppm and a residual styrene monomer content of not more than 7,000 ppm;

the inorganic fine particles being in an amount of 0.01 to 0.6 weight %, said particles having an average particle size of 0.01 to 1 μ

m and are selected from the group consisting of lithium fluoride, borax, magnesium carbonate, magnesium phosphate, magnesium oxide, magnesium chloride, mangesium acetate, magnesium fluoride, magnesium titanate, magnesium silicate, talc, calcium carbonate, calcium phosphate, calcium phosphite, calcium sulfate, calcium acetate, calcium terephthalate, calcium hydroxide, calcium silicate, calcium fluoride, calcium titanate, strontium titanate, barium carbonate, barium phosphate, barium sulfate, barium phosphite, titanium dioxide, titanium monooxide, titanium nitride, zirconium dioxide, zirconium monooxide, molybdenum dioxide, molybdenum trioxide, molybdenum sulfide, manganese chloride, manganese acetate, cobalt chloride, cobalt acetate, copper iodide, zinc oxide, zinc acetate, aluminum oxide, aluminum hydroxide, aluminum fluoride, aluminosilicate, silicon oxide, graphite, carnallite, kainite, isinglass and pyrolusite; and

the stretching is carried out at a rate of 1×

10 to 1×

10⁵ %/minute; and

the film having a thickness of 0.5 to 500 μ

m.

11. The process according to claim 5, wherein the heat treating is carried out at a temperature of between a melting point and 100°

C. or more and the melting point and 5°

C. or less for no more than 3 minutes.

12. The process according to claim 6, wherein the chemical and/or physical treatment:

is selected from the group consisting of UV irridation treatment, plasma treatment, flame treatment and ozone treatment.

13. The process according to claim 1, wherein the film has a F-5 value in the machine direction and the transverse direction of at least 9 kg/mm² and a ratio of a F-5 value in the machine direction and the transverse direction of 0.75 to 1.25.

14. The process according to claim 1, wherein said stretching and restretching being carried out in the following three stages:

first stage;

uniaxial stretching in the machine direction

second stage;

uniaxial restretching in the transverse direction

third stage;

uniaxial restretching in the machine direction.

15. The process according to claim 1, wherein said stretching and restretching are carried out in the following two stages:

first stage;

biaxial stretching in the machine direction and the transverse direction and

second stage;

uniaxial restretching in the machine direction.

7. A process for production of a rolled film product, comprising cooling and rolling a pre-molded product obtained by extruding or press molding of a styrene polymer having a high degree of syndiotactic configuration or a composition thereof such that there is a decrease of thickness of the film from 1 to 30%.

8. The process according to claim 7, wherein the rolling is carried out at glass transition temperature to 10°

C. lower than melting point.

9. The process according to claim 7, which further comprises carrying out a chemical and/or physical treatment to partly or totally to obtain a surface tension of the film to not less than 35 dyne/cm².