JPS63312386A - Gasket - Google Patents

Abstract

PURPOSE:To obtain the titled gasket, having excellent shape stability at high temperatures, by using aromatic polyamide fibers having specific properties. CONSTITUTION:The aimed gasket obtained by using aromatic polyamide fibers having characteristics of Tm (melting point) >=350 deg.C; Tm-Tex (thermogenic starting point) >=30 deg.C; Xc (crystallinity) >=10% DE (elongation) >=10% DSR (Tm) [dry heat shrinkage at the melting point (Tm)] <=15% and the formula [DSR (Tm+55 deg.C) is dry heat shrinkage (%) at the melting point +55 deg.C]. Furthermore, the above-mentioned fibers are preferably fibers produced from an aromatic polyamide having 1-4C lower alkyl or functional groups selected from amino, sulfone, carboxyl and hydroxyl group or halogen atoms. in the o-position of phenylene groups directly linked to N and/or C of amide bonds.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a gasket material used for gaskets, gland backings, pipe joints, etc., and an object of the present invention is to provide a gasket material that has particularly excellent morphological stability at high temperatures.

[Conventional technology]

Gasket materials are formed by kneading heat-resistant fibers, inorganic fillers, and binders into a sheet, or by wet-forming these raw materials and press-molding them into a sheet. The materials used for these are based on the environment in which the gasket material is used.
Heat-resistant materials are used. Asbestos and glass fibers are mainly used as heat-resistant fibers, but in recent years the use of organic heat-resistant fibers has been considered due to pollution problems caused by asbestos' carcinogenic properties. A typical fiber thereof is a meta-based wholly aromatic polyamide fiber, whose chemical composition is mainly composed of polymetaphenylene isophthalamide (hereinafter abbreviated as 1'MIA).

[Problem that the invention seeks to solve]

Since asbestos is commercially resistant to heat, gasket materials made from it have high dimensional stability even at high temperatures. PMIA fibers have the property of rapidly shrinking due to heat at around 450° C., and gasket materials made from them have the disadvantage that they are inferior in dimensional stability to those made of asbestos.

゛ In view of the above-mentioned problems with the delicate nature of PMI A, the present inventors have achieved dimensional stability by using a heat-resistant organic synthetic fiber that has morphological stability at high temperatures, that is, has small heat shrinkage even at high temperatures above the melting point. This led to the invention of a gasket material with excellent properties.

[Means for solving problems]

That is, the present invention has Tm2350°C, Tm-Tex23
0℃, Xc≧10%, DE≧10%, DAB (Tm)
We have discovered that by using 515% D8B(Tm) fibers as heat-resistant fibers for gasket materials, it is possible to obtain dimensional stability comparable to that of asbestos, which was not possible with conventional aromatic polyamide fibers (PMIA fibers).

Note that the characteristic values and physical property values referred to in the present invention represent numerical values obtained using the measuring equipment and measurement conditions described below, respectively.

Tm: Melting point; I) Using SC-20 manufactured by PerkinElmer Co., a sample of approximately 10.9 was placed in an AA' sample dish and heated at 10°C per minute in a nitrogen gas flow (3077 J/min) from room temperature to a specified temperature. A DSO curve is drawn, and its endothermic peak temperature is defined as Tm.

Tex: Heat generation start temperature; PerkinElmer DS
Using G-20, place approximately 10 mg of the sample in an An sample dish and draw an 8G curve from room temperature to the specified temperature in an air stream (30 mA/min) at 10°C per minute, and let the temperature at which the heat starts to heat up to be Tex. .

Crystallinity: Xc; Rotating anticathode ultra-high intensity X-ray generator BAD-rA (40KV 100mA, 0
The sample is rotated in a plane perpendicular to the X-ray beam to obtain an X-ray diffraction intensity curve in the range of diffraction angles 2θ-5° to 35°, and then the diffraction curve is ) and an amorphous region (Aa), and the value Xc calculated from the following formula is defined as the degree of crystallinity.

Xc = -X 100 (g) Ac+Aa DE: Elongation of fiber; using Instron tensile tester, sample length 10CI11, drawing speed 5cM/min, initial load o, o s
It was determined by conducting a tensile test under the condition of g/d.

DAB: Dry heat shrinkage; after applying a load of O.tg/d to the fiber sample and measuring its length lO, it is free-treated in a hot air dryer at a predetermined temperature for 10 minutes, and then 30 minutes later, it returns to 0.0. Measure the sample length 11 by applying a load of 1 g, /a,
The dry heat shrinkage rate DAB was determined using the following formula.

lO Aromatic polyamide fibers represented by specific physical properties in the present invention include, for example, a lower alkyl group having 1 to 4 carbon atoms, or an amine group at the ortho position of a phenylene group directly connected to the nitrogen atom and/or carbon atom of the amide bond. , a sulfone group, a carboxyl group, a hydroxyl group, etc., or an aromatic polyamide having a norogen atom. The substituent present at the ortho-position of the phenyl group of the aromatic polyamide may be any substituent as long as it satisfies the physical properties of the fiber, but those described above are preferred. Most preferred are lower alkyl groups having 1 to 4 carbon atoms.

The characteristic values and physical property values of the aromatic polyamide fiber used in the present invention will be explained.

Tm (melting point) is 350℃ or higher, rarely Te
When x (exotherm onset temperature) is lower by 30°C or more and Xc (crystallinity) is 10% or more, the fiber has excellent nob state stability even at high temperatures above the melting point.

In other words, Tm5350℃ and Xc≧10%
Even if Tm-Tex is 30°C or higher,
When comparing fibers with lI'm-Tex of less than 30°C, the former, that is, 'l'ex (thermal decomposition initiation temperature) is Tm (melting point)
The shape stability of the fiber at high temperatures above Tm (melting point) is better when the temperature is 30°C or more lower than the latter, that is, when the Tex is lower than Tm by 30°C. This may seem unreasonable, but quite surprisingly, lower Tex actually shows better morphological stability.

I don't really know the exact reason for this, but Tm53
In the case of aromatic polyamide fibers where 50°C, Xc≧10% and Tex is 30°C or more lower than Tm, thermal decomposition starts from a relatively low Tex, so it occurs slowly and mainly in the amorphous region, and at that time, Since the microcrystals exist without melting in the crystalline region, the shrinkage is suppressed because the microcrystals act as restraint points for the molecular chains against thermal contraction that occurs when the orientation of the oriented molecular chains in the amorphous region is relaxed due to heat. Tsutsu,
It is thought that a type of crosslinking occurs between molecular chains as a result of the thermal decomposition reaction that proceeds simultaneously, forming a three-dimensional structure, resulting in good morphological stability even above the melting point.

On the other hand, even if Tm5350℃ and Xc≧10%, if Tex or Tm is lower than 30℃, thermal melting will occur before a three-dimensional structure is formed due to sufficient intermolecular crosslinking. It is thought that heat shrinkage and fusion between fibers became large, resulting in poor shape stability.

Therefore, the range of Tm-Tex must be Tm-Tex 230°C, preferably Tm-Tex≧50°C, and more preferably Tm-Tex 270°C.

In addition, other fiber properties deteriorate to some extent at Tm or higher, so in order to be a heat-resistant fiber that can be used at temperatures 200°C or more higher than general synthetic fibers, Tm must be 5350°C, preferably 52400°C. As mentioned above, it is generally preferable that Tm≧420°C or higher.

In addition, even if Tm5350℃ and Tm -Tex≧30℃, if the crystallinity is small (Xc<10%), there is almost no restraining effect on molecular chain movement by microcrystals, so T
From around the glass transition point, which is much lower than m, the thermal shrinkage increases rapidly and the shape stability becomes poor.

For the reasons mentioned above, it is necessary that Xc≧10%,
Preferably, lc≧15%.

In order for Zaraani fiber to be used in the same way as existing organic synthetic fibers, it is essential that it has good flexibility and processability.

For this purpose, it is important to have a sufficient balance between strength and elongation, especially elongation, and DE (fiber elongation) must be 210%. Preferably DE>15%, most preferably DE>2 o 96. In addition, as an aspect that greatly increases the morphological stability at high temperatures, fibers or D S
ill (Tm) 515%.

When Doll (Tm) exceeds 1596, the dry heat shrinkage is already large at the melting point, and the shape stability cannot be said to be good. D8 E (Tm) Even if it is 515%, D8
B (Tm+55°C) Since thermal shrinkage increases rapidly, this is not preferable for use as a heat-resistant gasket, which is the object of the present invention. However, it is important that the thermal shrinkage is sufficiently small even at temperatures considerably higher than the melting point.

The method for producing aromatic polyamide fibers having such specific physical property values is not particularly limited, but for example, as described in Japanese Patent Application No. 117970/1987 filed separately by the present inventors, A polymer in which 95 mol% or more of the repeating units is 4-methyl-1,3-phenylene terephthalamide and/or 6-methyl-1,3-phenylene terephthalamide is used as the spinning stock solution, and the stock solution temperature is set at 20 to 20 mol%.
Metal salts such as CaC1)4, Zn(JJI2, Li
(262, LiBr etc. is wet-spun in an aqueous solution containing 10-510-5O at a temperature of 30 to boiling point temperature, preferably 50 to 100°C, and then 1. .1 to 5 times wet heat stretching, then 5 times
After thorough washing in hot water of 0 to 100℃,
Hot air drying at ~200℃, followed by 300℃~450℃
It is manufactured by carrying out a dry heat stretching heat treatment of 1.1 to 5 times in a window atmosphere or an inert gas bath. During this wet spinning, it is possible to form irregularities on the surface of the resulting fiber depending on the properties of the coagulation bath, and if the fiber has such an uneven surface, it will have a better effect on its spinnability. .

Next, aspects of the present invention will be specifically explained with examples, but the present invention is not limited by these examples.

Example 1 Terephthalic acid 166, OQ (0,9991 mol), 2.038 g of terephthalic acid monopotassium salt, anhydrous, in a 31-capacity separable flask equipped with a stirrer, thermometer, condenser, dropping funnel, and nitrogen inlet tube. 1600 yyu of N,N'-dimethylethylene urea is charged under a nitrogen atmosphere and heated to 200° C. with stirring on an oil bath. tolylene-24-diisocyanate 174. while maintaining the contents at 200°C. OQ (0,9991 mol) in anhydrous N
A solution dissolved in 160 ml of N'-dimethylethylene urea was added dropwise from the dropping funnel over a period of 4 hours, and after the reaction was continued for approximately 1 hour, heating was stopped and the mixture was cooled at room temperature. After the reaction, a portion was taken and poured into strongly stirred water to precipitate a white polymer, and washed with a large amount of water.
Logarithmic viscosity of the polymer obtained by drying under reduced pressure at 0°C for about 3 hours (
95%R2SO40,1y/dll, 30℃) is 2.2
Met. The polymer concentration of the polymerization solution was approximately 11.0% by weight, and the viscosity of this solution was 420 poise (B-type viscometer: 5
It was 0℃. In addition, the obtained polymer was determined by Ill spectrum and NMB spectrum from poly(4-methyl-1,
3-phenylene terephthalamide).

The above polymerization solution is degassed under reduced pressure at 50° C. to prepare a spinning dope that does not contain air bubbles. Then, while keeping the temperature at 50℃, the pore size was adjusted to 0.11.
54 mm, into an aqueous coagulation bath containing 40% Oa (M2) maintained at 80 °C from a nozzle with 600 holes (the holes are circular).
．． Discharge at 59 portions. After passing through a coagulation bath, the coarse threads discharged from the nozzle are subjected to moist heat stretching at a ratio of about 16 times in a bath with the same composition as the coagulation bath, followed by thorough washing in a water wash bath consisting of approximately 80°C warm water, followed by an oil solution. The mixture is applied and dried through a hot air bath at 150° C. to obtain a wet heat drawing method spun yarn.

The spinning yarn has an oval cross section but is homogeneous and has a diameter of 2900
It was a 7'neel/600 filament.

Next, this spun yarn was subjected to dry heat stretching at a stretching ratio of 2.4 times using a nitrogen flow hollow dry heat stretching machine maintained at 430°C.
] Two elm terephthalamide) fibers were produced.

The physical properties of the obtained fibers are: single yarn denier = 2, strength = 5
．． 8 ct/dr, elongation = 254LX), Young's modulus = 8
8y/d, Tm=42s℃, Tex=95℃,
Tm-Tex=95°C, Xc=24%, DS l(('
I'm) = DS B 42' 5°C = 11%, D8B(Tm) DAB (425°C)
13%, which numerically indicates good general fiber physical properties and excellent shape stability at high temperatures above the melting point.

75 parts of 31ran cut fiber of this fiber, 10 parts of silicone rubber, 10 parts of talc as a filler, and 2.5 parts each of other vulcanizing agents and stabilizers were added, kneaded with rolls, and then put into a mold. Heat and pressure molded under the conditions of 160℃ x 200 kgAi, inner diameter 40 + + + m, outer diameter 70 m
, a gasket with a thickness of 3711 m was molded.

This gasket was left at a high temperature of 450° C. for 1 minute, but almost no deformation of the gasket was observed.

Comparative Example 1 21 equipped with a stirrer, thermometer, and jacketed dropping funnel
250.29 (1,232 mol) of isophthalic acid chloride and 600 ml of anhydrous tetrahydrofuran were put into a separable flask with a jacket to form a solution H, and the contents were cooled to 20° C. by passing a refrigerant through the jacket. A solution of 133.7 g (1,237 mol) of metaphenylenediamine dissolved in 400 ml of anhydrous tetrahydrofuran was added dropwise over about 20 minutes with strong stirring. The obtained white emulsion was quickly poured into water (water-cooled) containing 2.464 mol of anhydrous sodium carbonate under strong stirring. Immediately, the slurry temperature rose to near room temperature. Subsequently, after adjusting the pH to 11 with caustic soda, the slurry was separated, and the resulting cake was thoroughly washed with a large amount of water and dried overnight under reduced pressure at 150°C. The logarithmic viscosity of the polymer was 1.4.

Preparation The poly(metaphenylene isophthalamide) or PMIA polymer powder was mixed with N-methyl-2-pyrrolidone (
NMP ) and 296 adjusted for NMP. Then 8
CaCj? maintained at 80°C from a nozzle with a hole diameter of 0.08 and 100 holes (the holes are circular) kept at 0°C. 240
% into an aqueous coagulation bath containing
After passing through a rotating roller and thoroughly rinsing with water in an 80°C hot water bath, it was then subjected to wet heat stretching at 2.88 times in 98°C hot water using rollers, and after applying an oil agent to Zara, it was washed with hot air at 150°C. The yarn was dried by passing it through a tank to obtain a spun yarn that had been subjected to wet heat stretching. The spun yarn had a homogeneous cocoon-shaped cross section and was 358 denier/100 filaments.

Next, this spun yarn was subjected to dry heat stretching of 1.88 times on a plate at 310°C to obtain poly(metaphenylene isophthalamide) fiber.

The physical properties of the obtained fibers are: single yarn denier = 2, strength = 4
．． 9 Q/d, elongation = 28.5%, Young's modulus = 80y
/rl, Tm=42 s℃, Tex=405℃, Tm
-Tex=20℃, Xc=25%, ])S B (Tm
)=D8]((425℃)=16%, DAB(Tm+ss℃) D8B(480℃)
61%, and although this PMI human fiber exhibited good general fiber physical properties, it was clearly inferior to Example 1, which is the present invention, in terms of shape stability at high temperatures above the melting point.

A gasket is formed from this fiber in the same manner as in Example 1, and when it is left at a high temperature of 450 Yl for 1 minute, the gasket is greatly deformed and has a shrinkage rate of 2096 in terms of dimensional change rate, which is poor in heat resistance.

Claims (1)

[Scope of Claims] 1. A gasket made of aromatic polyamide fiber having characteristics satisfying the following formula. Tm≧350℃ Tm-Tex≧30℃ Xc≧10% DE≧10% DSR(Tm)≦15% [DSR(Tm+55℃)]/[DSR(Tm)]≦3
(Here, Tm is the melting point (℃), Tex is the humidity at which heat generation starts (℃)
), Xc is crystallinity (%), DE is elongation (%), DSR
(Tm) is dry heat shrinkage rate (%) at melting point Tm, DSR
(Tm+55℃) is the dry heat shrinkage rate at the melting point +55℃ (
%). ) 2. The aromatic polyamide fiber has a lower alkyl group having 1 to 4 carbon atoms, or an amino group, a sulfone group, or a carboxyl group, in the ortho position of the phenylene group directly connected to the nitrogen atom and/or carbon atom of the amide bond,
2. The gasket according to claim 1, which is a fiber made of aromatic polyamide having a functional group selected from hydroxyl groups or a halogen atom.