US4596837A
Expired / Lapsed
US
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Semisintered polytetrafluoroethylene article and production thereof
Assignee: Daikin Industries Ltd
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Filing: 1984-08-21
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Granted: 1986-06-24
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Expires: 2004-08-21
Abstract
Abstract A semisintered polytetrafluoroethylene article which is prepared by heating an unsintered polytetrafluoroethylene article at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345+/-5 DEG C. on a crystalline melting chart measured with a differential scanning carolimeter and a crystalline conversion of from 0.10 to 0.85 defined by heat of fusion of the unsintered, semisintered and sintered polymer, and the crystallinity of the semisintered article measured by X-ray diffraction being from 80 to 93%. The article is expandable biaxially to afford a porous polytetrafluoroethylene material having an almost unporous surface.
Inventors
- 👤 Katsutoshi Yamamoto
- 👤 Shoji Kawachi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:42
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; B; B29; B29C; B29C48/00; B29C48/022; B29C55/00; B29C55/005; B29C55/02; B29C55/10; B29C55/12; B29C67/00; B29C67/02; B29C67/04; C08J9/00; B29C48/03; B29C48/07; B29C48/08; B29K; B29K2027/00; B29K2027/12; B29K2027/18; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18; Y; Y10; Y10S; Y10S521/00; Y10S521/919
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
106 words
A biaxially stretchable semisintered polytetrafluoroethylene article having good tensile strength and smooth surface proportions which is prepared by heating an unsintered polytetrafluoroethylene article which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.10 to 0.85 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 80 to 93%.
Claim 2
Dependent Claim
106 words
A biaxially stretchable semisintered polytetrafluoroethylene article having good tensile strength and smooth surface proportions which is prepared by heating an unsintered polytetrafluoroethylene article which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.10 to 0.85 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 80 to 93%.
Claim 3
Dependent Claim
16 words
The semisintered article according to claim 1, wherein the crystalline conversion is from 0.15 to 0.70.
Claim 4
Dependent Claim
15 words
The semisintered article according to claim 1, wherein the crystallinity is from 85 to 92%.
Claim 5
Dependent Claim
23 words
The semisintered article according to claim 1, wherein the specific gravity of the heated surface of the semisintered article is at least 1.80.
Claim 6
Dependent Claim
19 words
The semisintered article according to claim 1, wherein the unsintered article has a specific gravity of at least 1.4.
Claim 7
Dependent Claim
24 words
The semisintered article according to claim 1, wherein the unsintered article is a sheet or a film having a thickness less than 0.2 mm.
Claim 8
Dependent Claim
47 words
The semisintered article according to claim 1, wherein the unsintered article is a sheet or a film having a thickness of at least 0.2 mm, a tube having a wall thickness of at least 0.2 mm or a rod having a diameter of at least 0.2 mm.
Claim 9
Dependent Claim
108 words
A process for producing a biaxially stretchable semisintered polytetrafluoroethylene article having good tensile strength and smooth surface properties which comprises heating an unsintered polytetrafluoroethylene article which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.10 to 0.85 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 80 to 93%.
Claim 10
Dependent Claim
108 words
A process for producing a biaxially stretchable semisintered polytetrafluoroethylene article having good tensile strength and smooth surface properties which comprises heating an unsintered polytetrafluoroethylene article which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.10 to 0.85 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 80 to 93%.
Claim 11
Dependent Claim
32 words
The process according to claim 8, wherein the heating is carried out at a temperature of from the melting point of the sintered polymer to the melting point of the unsintered polymer.
Claim 12
Dependent Claim
29 words
A process for producing a porous polytetrafluoroethylene material, which comprises expanding a semisintered article according claim 1 at a temperature lower than the melting point of the unsintered polymer.
Claim 13
Dependent Claim
12 words
A porous polytetrafluoroethylene material prepared by the process according to claim 10.
Claim 14
Dependent Claim
131 words
A biaxially stretchable and expandable semisintered polytetrafluoroethylene article having a specific gravity of at least 1.8, good tensile strength and a nonporous surface substantially free of particles and band structure which is prepared by heating an unsintered polytetrafluoroethylene article having a specific gravity of from 1.2 to 1.7 which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.15 to 0.70 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 85 to 92%.
Claim 15
Dependent Claim
131 words
A biaxially stretchable and expandable semisintered polytetrafluoroethylene article having a specific gravity of at least 1.8, good tensile strength and a nonporous surface substantially free of particles and band structure which is prepared by heating an unsintered polytetrafluoroethylene article having a specific gravity of from 1.2 to 1.7 which has been obtained by paste-extrusion of polytetrafluoroethylene fine powder at a temperature of at least the melting point of a sintered polymer, the article having an endothermic curve at a temperature of 345°±5° C. on a crystalline melting chart measured with a differential scanning carolimeter and the crystalline conversion of from 0.15 to 0.70 defined by heat of fusion of the unsintered, semisintered and sintered polymers, and the crystallinity of the semisintered article measured by X-ray diffraction being from 85 to 92%.
Claim 16
Dependent Claim
20 words
The semisintered article according to claim 12, wherein the specific gravity of the semisintered article is from 2.20 to 2.25.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-06-23 | 1989-12-23 | 1990-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-23 | 1993-12-23 | 1994-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-23 | 1997-12-23 | 1998-06-24 | $7700.00 | Window Closed / Lapsed |