JPH07324296A - Improved pressboard - Google Patents

Abstract

PURPOSE: To obtain an improved aromatic polyamide pressboard having the combination of good resistance against compression, with proper oil absorption. CONSTITUTION: This high density pressboard comprises 20-95 wt.% aromatic polyamide fibrid and 80-5 wt.% high temperature-resistant flock, and has 13-28 vol.% calculated void volume of the pressboard, 0.5-50 mm thickness, <0.20 cm<3> /g mercury intrusion volume Vml at a low surface/volume ratio, 0.08-0.28 m<3> /g mercury intrusion volume Vmh at a high surface/volume ratio, 0.09-0.28 oil absorption Vo by volume in cm<3> /g, 8-24 wt.% oil absorption by weight, and the total available absorption volume Va in cm<3> /g equal to the largest of the values of Vml, Vmh and Vo. The ratio of the Va to the Vml is at least 1.1, and the pressboard is characterized by having a compression set larger than 0.12 mm but less than 0.5 mm.

Description

Detailed Description of the Invention

The present invention relates to an improved aromatic polyamide pressboard having increased resistance to compression combined with relatively high oil absorption properties.

Pressboard made from cellulosic materials is known and has been in commercial use for many years. Although cellulosic pressboards are very useful, their use at elevated temperatures is limited by the low thermal stability of cellulosic materials. Recently, aromatic polyamide fibers (US Pat. Nos. 3,063,966 and 3,133,138) having excellent properties at high temperatures, fibrids (US Pat. No. 2,999,788), and Paper (US Pat. No. 3,756,908) came to be known. Pressboards composed of aromatic polyamide fibers and fibrids (also known as fibrids) are also known and can be easily manufactured using the same methods used in the manufacture of cellulosic pressboards.

Aromatic polyamide pressboards have been found to be useful in many applications. For example, in oil-filled transformers, it has been found to have a reasonably high oil absorption that contributes to good electrical insulation properties. However, for some applications, not only does the pressboard have a reasonably high oil absorption, but the pressboard also provides a suitable separation of electrically conductive components.
It is also necessary to provide resistance to compression so that ration) can be provided. By the compaction process as taught by the prior art does not give a pressboard product with sufficient resistance to compression or they obtain a pressboard product with insufficient oil absorption. It has been found to obtain a pressboard product that has sufficient resistance to compression only.

The present invention provides an improved aromatic polyamide pressboard having a combination of good resistance to compression and suitable oil absorption.

The present invention is directed to aromatic polyamide fibrid 20.
A high density pressboard comprising -95% by weight and 80-5% by weight high temperature resistant block, the pressboard having a calculated void volume of 13-28% by volume of the pressboard,
0.5 to 50 mm thickness and 0.5 at low surface / volume.
20 cm ³ / and g is less than the mercury intrusion volume Vml, mercury intrusion volume Vmh of 0.08-0.28Cm ³ / g at high surface / volume, expressed in cm ³ / g .09 to 0.
A volumetric oil absorption Vo of 28 and a weight oil absorption of 8-24% by weight, and a total effective absorption volume Va expressed in cm ³ / g equal to the maximum of the values of Vml, Vmh and Vo, The ratio of Va to Vml is at least 1.1, the pressboard is larger than 0.12 mm but 0.5 m
Provided is a high density pressboard characterized by having a compression set (defined below) not greater than m. Preferably, the pressboard is an aromatic polyamide fibrid 5
It consists of 0-70% by weight and 30-50% by weight of high temperature resistant flocks. Preferably the high temperature resistant block comprises aromatic polyamide and the pressboard is 1.00-1.
It has a density of 20 g / cm ³ . Preferably the aromatic polyamide fibrids and high temperature resistant flocs are essentially poly (m-phenylene isophthalamide) (MPD-I).
Consists of. The pressboard is preferably composed of aromatic polyamide fibres and flock and has a thickness of 1-10 mm, a density of 1.02 to 1.17 g / cm ³ , most preferably 1.10-1.15 g / cm ³ . Have a density. Preferably the pressboard has a compression set of 0.12-0.35 mm, most preferably 0.20-0.30 mm.

The improved pressboard is an aromatic polyamide fibrid 20-95 having a melting point above 320 ° C.
2-12mm with wt% and melting point higher than 320 ° C
Of an aqueous slurry having a total solids content of 0.1 to 2% by weight consisting of 80-5% by weight of a high temperature resistant floc having a length of 50 to 95% by weight on a waterleaf having a water content of 50 to 95% by weight. The wet trap is formed by combining the unsized papers so as to form a multi-layer, and the wet trap is subjected to 100-2 under a pressure of 10-60 kg / cm ^2.
Press at 00 ° C to form a low density pressboard having a calculated void volume of 30-60% by volume of the pressboard, which is finally 270- until substantially no more water is generated. It is produced by a method which comprises drying at 320 ° C. and finally pressing at 8-270 kg / cm ² at 270-320 ° C. Preferably the temperature is 275-300 ° C. Most preferably the final pressing step is 275-285 ° C and the pressure is 1
It is 5-70 kg / cm ² . Preferably the pressboard is cooled under restraint. Preferably the high temperature resistant block comprises an aromatic polyamide. Preferably the aromatic polyamide fibres and the high temperature resistant flocks consist of poly (m-phenylene isophthalamide).

"Aromatic polyamide" means the amide group of each repeating unit, ie

[0008]

[Chemical 1]

Non-melting, wherein R is hydrogen or an alkyl group of 1-6 carbons, is attached via a nitrogen atom and a carbon atom to a carbon atom in the ring of another aromatic ring group. Means nonfusible polyamides. The term "aromatic ring" is defined herein as a carbocyclic ring having resonance.

"Aromatic polyamide fibrids" means 3
By small, non-granular, non-rigid fibrous or film-like particles having a melting point above 20 ° C. Two of those three dimensions are on the order of microns. Their smallness and suppleness are physically entwined as is commonly found in paper made from wood pulp.
ed) Allowed to be deposited in the structure. Fibrids are described, for example, in U.S. Pat. No. 3,018,09.
It can be produced by precipitating a solution of an aromatic polyamide in a coagulant in a device of the type disclosed in No. 1.

"High temperature resistance block (high temperature
"resistant floc)" means a material having a melting point higher than 320 ° C., such as aromatic polyamides, aromatic polyamide-imides, aromatic polyimides, polybenzimidazoles, etc., or inorganic materials such as glass, ceramic materials, Typically 2-1 made from alumina, etc.
It means a short fiber having a length of 2 mm and a linear density of 1-10 decitex. Other high temperature resistant materials, such as mica, can also be present in a relatively finely divided form.

"Aromatic polyamide floc" is the method described in US Pat. Nos. 3,063,966, 3,133,138, 3,767,756 and 3,869,430. By short fibers cut from the fibers produced.

A conventional aromatic polyamide pressboard is
MPD-I fibrids and MP
An aqueous slurry of MPD-I floc was fed to a cylinder paper forming machine to remove water and remove 50 of the wetted sheet.
Multiple layers of fiber material with a water content of -95% by weight (mu
ltiple layers) with the desired thickness (wet l
It can be manufactured by configuring ap). The wet trap is cut from the cylinder, laid flat and pressed at 100-200 ° C. under a pressure of 10-60 kg / cm ² . The conventional pressboards obtained usually have a high oil uptake of 20-50% by weight, a density of about 0.7-0.9 g / cm ^3, a low calculated void volume of about 35-50% by volume of the pressboard. And high surface /
Total effective absorption volume expressed in cm ³ / g for mercury intrusion volume Vml at about 0.30~0.50cm ³ / g mercury intrusion volume, low surface / volume in the volume (total avail
It has a ratio of an absorption volume (Va) of about 1 and a compression set of 0.75 to 2.5 mm.

However, for some applications, such as spacers used in oil-filled transformers, the compression set desirably retains an oil absorption of at least 8% and is less than about 0.12 mm. Should not
Or it should not be larger than about 0.5 mm. About 0.1
Pressboards with compression set values of less than 2 mm do not have the combination of compressibility and resilience necessary to maintain proper spacing of electrical components in, for example, transformers. Similarly, pressboards with compression set greater than 0.5 mm do not maintain proper spacing of the parts.

The above desired properties are provided by the product of the present invention. The low density pressboard having a calculated void volume of 30-60%, prepared as described above, is finally processed to 270-320 until substantially no more water is generated.
Further drying at a temperature of ℃, then 270-320 ℃ and 8
And pressed at a pressure of -350kg / cm ^2, and preferably subsequently cooled under restraint, has been found to pressboard having the desired characteristics can be obtained. Drying is preferably
This is achieved by a gradual increase in temperature. Moisture generation is facilitated by the application and release of light pressure. Generally, the pressing operation is preferably 15-70 kg
At 275-300 ° C./cm ² for at least 5 minutes, but thicker products require longer pressing times. More than one layer of low density pressboard can be combined during the hot pressing operation. In this case, longer press times should be used. Preferably, the hot pressing operation is performed at a glass transition temperature (T) of the aromatic polyamide constituting the fibrids.
g) should be higher. The glass transition temperature is about 275 ° C. for the preferred poly (m-phenyleneisophthalamide) fibrils.

A wet trap is formed from multiple layers of waterleaves having a water content of 50-95%, and the wet trap is 10-60 kg / cm ^2.
Press at 100-200 ℃ under the pressure of 30-60%
Manufactures a low density pressboard with a calculated void volume of
The low density pressboard is then dried and 8-
The above method, which involves pressing again at 270-320 ° C. under a pressure of 350 kg / cm ² , has been found to be essential for obtaining a pressboard product that exhibits good resistance to compression and sufficient oil absorption. Was issued. If the low density pressboard has a calculated void volume of less than 30%,
Oil absorption of final pressboard products tends to be very poor.

The pressboard of the present invention is useful in clamping rings and axial and radial spacers in oil-filled electrical transformers.

The product of the present invention is a pressboard 13-2.
A calculated void volume of 8% by volume, a mercury penetration volume Vml of less than 0.20 cm ³ / g at low surface / volume, and a mercury penetration volume Vmh of 0.08-0.28 cm ³ / g at high surface / volume; 0.08-expressed in cm ³ / g
A volumetric oil absorption Vo of 0.28 and a weight oil absorption of 8-24%, a total effective absorption volume Va in cm ³ / g equal to the maximum of the values of Vml, Vmh and Vo, and at least 1. And the ratio of Va to Vml is 1.
Calculated void volume greater than 28% or Vml of 1.0
Pressboards with a ratio of Va to VA generally have poor compression set, while pressboards with a calculated void volume of less than 13% or Vmh of less than 0.08 cm ³ / g generally exhibit poor oil absorption. . The products according to the invention have Va values which are very different from the Vml values, their ratio being at least 1.1 and a high value of 4.

Test Density A dried pressboard is cut into squares at least 10c, ensuring that the top and bottom surfaces of the sample are the same area and the dimensions are accurately measured.
It is cut into rectangular samples with dimensions of m × 10 cm (4 inches × 4 inches), preferably at least 20 cm × 20 cm (8 inches × 8 inches). The length and width of rectangular samples are measured to an accuracy of at least 0.25 cm (0.1 inch). The thickness of the rectangular sample of the pressboard is about 0.1 kg at a pressure of about 0.1 kg / cm ² (about 1.25 psi).
10 at least 10 locations spaced substantially evenly around all sides of the pressboard using a micrometer caliper in contact with a surface having a diameter of 6 cm (0.25 inch). Average the thickness measurements from each run to an accuracy of at least 0.125 mils. The pressboard sample is then weighed to an accuracy of 0.0001 g (the nearest 0.0001 g). Then press sample volume Vo
Is calculated in cm ³ and the weight is divided by the volume to obtain the density in g / cm ³ .

Calculated void volume The void volume Vv expressed in cm ³ of the sample of the press board is expressed by the relational expression V _b = V _m + V _v or V _v = V _b −V _m (where V _b is The volume of the pressboard determined in cm ³ determined above, V _m is the total volume of all the materials that make up the pressboard, expressed in cm ³ , and V _v is the void volume, in cm ³ . Is the remaining volume expressed). V _m is determined from the weight and density of each of the materials that make up the pressboard sample, calculated as follows:

[0021]

[Equation 1]

Where W _f is the weight of the aromatic polyamide fibrids in the pressboard sample, expressed in g, and W _f
i is the weight in g of the flock (including any other non-fibrid high temperature resistant material) in the pressboard sample, and ρ _i is the density of the material forming the flock (MP
1.38 g / cm ³ ) for DI and 1.4 for poly (p-phenylene terephthalamide).
Is a 4g / cm ^3]. If there is more than one block (or other high temperature resistant material such as mica), W _i / ρ _i is calculated as follows:

[0023]

[Equation 2]

(Where i = 1, ... N).

The void volume V _v , calculated as a percentage volume,%, is then calculated as follows:

[0026]

[Equation 3]

For a 100% MPD-I pressboard sample having a weight of W _b in g and a volume of V _{b in} cm ³ , for this case

[0028]

[Equation 4]

Therefore, the above equation becomes

[0030]

[Equation 5]

Is transformed into

The calculated void volume is a measure of all voids in the pressboard sample, both isolated voids and interconnected voids.

Oil absorption This test is based on the International Electrotechnical Commission.
The method described by the Otechnical Commission, the Central Secretariat of the International Electrotechnical Commission in Geneva, Switzerland (Bure
au Central de la Commission Electrotechnique Inter
nationale Geneva, Switzerland),
IEC Standard, Publication 641-2, First Edition (1979),
Standards for pressboards and presspapers for electrical purposes, Part 2, Test methods, pages 29 and 31 (section 17) (IEC Standard, Publication 641-
2, First edition (1979), "Specification for
pressboard and presspaper for electrical purpose
s, Part 2: Methods of test. ”pages 29 and 31
This is done according to (section 17). The results are expressed as a weight percentage oil uptake relative to the original weight of the tested pressboard samples to an accuracy of 0.1%. cm ³ /
The volumetric oil absorption, Vo, expressed in g, is then calculated by dividing the weight percentage oil absorption by the density of the pressboard sample. The Vo value is first reported to the same number of significant figures as the weight percent oil absorption, then rounded to the second decimal place.

Compression Set The pressboard to be tested was rectangular strip 3.8.
Cut into cm (1.5 inches) width x 5.1 cm (2.0 inches) length and stack a sufficient number of strips to make a stack about 5.1 cm (2.0 inches) high. to make. The sample stack was placed in an oven at 110 ° C for 48 hours, then removed from the oven and a constant speed crosshead movement.
And at least 10,000 kg (22,000
A conventional machine for testing compression properties having a capacity of [pounds] [e.g., Model MM Flatbed X-Y Recorder (Model MM Flat manufactured by Houston Instruments, Inc).
Bed XY Recorder) and the Teinius Olsen models D-2 and D- for accurately measuring the deflection of a sample compressed at two different chart magnifications.
4 Deflection meter (Tinius Olsen Model D-2 and D-4 D
eflectomers), Tinius Olsen Universal Testing Machine, Easton Earlday,
Willow Grove, PA 19090 (Tinius Olsen Un
iversal Testing Machine Co., Inc., Easton Rd., Will
OW Grove, PA 19090) manufactured by Teinius Olsen Universal Testing Machine, Model 60SDT, Servo Control, 60,000 lb capacity, Super L, UTM (Tinius Olsen Universal Testi)
ng Machine, Model 60SDT, Servo-controlled, 6
.000 lb, capacity, Super L UTM)]. When conducting the test, the load is 0.5 cm per minute
Applied and released at a constant rate of (0.2 in / min). 35 kg / cm ² (3,448 kPa; 500 p
A load of 680 kg (1,500 lbs), equivalent to si), is applied to the above stack of samples and then the load is immediately released to a load of 136 kg (300 lbs). 7 kg / cm ² (690 kPa; 100 psi)
This load is equivalent to the bedding pressure (bedding pressu
re), and the load is released to this bedding pressure during each cycle. Sample stacking is 70
It is cycled to 3,000 pounds equivalent to kg / cm ² (6,895 kPa; 1,000 psi) and returned to bedding pressure. Then it is 141kg / c
It is cycled to 7,000 pounds, equivalent to m ² (13,790 kPa; 2,000 psi) and returned to betting pressure.

Finally, it is 211 kg / cm ² (20,6
85kPa; 4,000psi equivalent to 4,082kg
(9,000 pounds), then back to bedding pressure. Compression set is measured as the loss of height (in mm (or mil)) of the stack of samples as measured by a flexometer upon return to bedding pressure after the final cycle. The flexometer readings are preferably plotted on the chart continuously so that the entire sequence of cycles is displayed graphically for each sample tested.

If the amount of sample material is limited,
The 3.8 cm x 5.1 cm rectangular strips are stacked to a smaller height, preferably at least 2.5 inches (1.0 inch) in height, and the deflection after the final cycle stacks the results to 5.1 cm ( Balanced to correspond to results obtained from 2.0 inches (scal)
e) Multiply by the appropriate coefficient.

Mercury Intrusion Volum
e) In this decision, a conventional mercury porosimeter [Amine Commerce Yury 60,000 psi max, Newport Scientific, Silver Spring, M
D20910 (Aminco Mercury 60,000 psin max,
Newport Scientific Co., Inc., Silver Spring, MD
20910)] is used to determine the volume of mercury that can be pressed into the pores or interconnected voids of a porous sample. To determine if the surface area of a given weight of pressboard has an effect on the volume of mercury that can be pressed into its pores, a low surface / volume sample and a high surface / volume of the pressboard [ Measurements are made on both the "subdivided" samples.

The nominal weight of each sample tested is 0.3 g. To prepare the low surface / volume and high surface / volume samples, an initial sample slightly heavier than 0.6 g and preferably rectangular is cut from the pressboard to be tested. The first sample is then immediately cut through the pressboard near its edge, in a series of about 25-35 clean cuts, to a given size (eg, by a pair of side cutters). Tsute (cut
down) forms a corresponding number of fragments, lower surface /
This leaves a preferably quadrilateral sample with a weight of about 0.3 g, which is used as the volumetric sample. This low surface / volume sample should, if at all possible, be shaped so that it fits tightly in the penetrometer valve (sample chamber) of the porosimeter. If the sample is very thin and a single piece with a weight of 0.3g that fits into the intrusion meter valve cannot be produced, a low surface /
Volumetric samples are manufactured in the form of two or three pieces that fit into a valve. Low surface / volume samples are weighed on glassine paper to an accuracy of 0.0001 g. A sufficient number of pressboard fragments to weigh about 0.3 g,
Preferably, about 25-30 pressboard fragments are placed on glassine paper as high surface / volume (smallly divided) samples (preferably they are collected on glassine paper when cut). The sample is weighed to an accuracy of 0.0001 g.

To make the determination, the weighed sample is placed in an open intrusion meter valve, then the valve is capped and evacuated until the vacuum gauge indicates a pressure of 50 microns of mercury or less. The filling device is then tilted backwards until it reaches its stop so that the tip of the intrusion meter is immersed in the mercury. Gradually open the stopcock on the filling device to allow air to enter the system gently to allow mercury to enter the intrusion meter valve and tap the tube to help wet the sample with mercury. After complete wetting is achieved, the filling device is returned to the vertical position. The intrusion gauge is then transferred from the vacuum chamber to the pressure chamber.

The pressure is then gradually increased and intrusion meter readings are recorded at intervals as the pressure increases. The device is usually, for example, about 350 kg / cm ² (34 M
Pa: 5,000 psi) and about 4200 kg / cm
^With more than one pressure gauge recording up to a maximum value of ² (414 MPa: 60,000 psi) and if so, the device is switched to a higher pressure gauge at the appropriate time as the pressure increases. 4200kg
An intrusion meter reading at / cm ² (414 MPa: 60,000 psi) is recorded at the end of the test. 4,200k
The mercury penetration volume in g / cm ² is determined from the intrusion meter reading according to the instructions given by the device manufacturer. Cm ³ / g for specific test pieces of pressboard
The mercury penetration volume values, expressed in cm ³ of mercury at 4200 kg / cm ² pressure per g of pressboard, were first determined to the fourth decimal place, then rounded and finally low and high surfaces / volumes (small The minority second place is reported for both of the (separated) samples. If desired
A graph of mercury penetration volume values over the entire pressure range is formed based on intrusion meter readings taken at intervals throughout the test. The mercury penetration volume at low surface / volume is represented by the symbol Vml and the mercury penetration volume at high surface / volume is represented by the symbol Vmh.

Total Available Absorp
tion volume) The total effective absorption volume Va of the pressboard sample is Vm of the sample
It is taken as equal to the maximum of the values of l, Vmh and Vo (all values are before rounding).
For any given sample of pressboard, Va is a measure of the volume, in cm ³ / g, of interconnected voids in the sample that are accessible to penetration by liquid.

Next, the ratio Va / Vml is calculated by using the values of Va and Vml before rounding in the calculation. In reporting this ratio, it is rounded to the first decimal place. Structures with limited or partial accessibility of internal voids in the pressboard, structures associated with good compression resistance of the pressboard when the calculated void volume of the pressboard is not more than 28%. Shows.

[0043]

EXAMPLES Example 1 A. "Preparation of Standard Pressboards " 1.5 Poly (m-phenylene isophthalamide) (MPD- with an inherent viscosity)
The filament of I) was dry spun from a solution containing 19% MPD-I, 70% dimethylacetamide (DMAc), 9% calcium chloride and 2% water. Upon leaving the drying tower, the as-spun filaments were given a pre-wash with water so that the filaments contained about 60% DMAc, 15% calcium chloride, and 100-150% water based on the weight of dry polymer. Contained. Cleaning the filament and the countercurrent extraction draw process (counter
In the current extraction-draw process), it was stretched 4 times at 90 ° C. The calcium chloride content and DMAc content, determined as chloride content in the process, were reduced to about 0.1% and 0.5%, respectively. The filament crystallized immediately after stretching by passing it over a hot roll at a temperature of about 340 ° C. The filaments so produced are 2.2 decitex (2.2.
Linear density of 0 denier, about 3.7 dN / tex (dN
/ Tex) (4.2g / denier) tenacity, 70
It had an initial module of dN / tex (79 gpd) and an elongation of 34%. The filament is 3.4 mm
It was cut into flock having a length of (0.135 inch).

MPD with an inherent viscosity of 1.5
The fibrid of -I was obtained by substantially eliminating the purification step.
U.S. Pat. No. 3,756,908 issued Sep. 4, 1973,
Prepared as described by Gross in col. 5, lines 34-54.

An aqueous slurry containing 1.0% by weight of fibrids and flocs having a composition of 60% MPD-I fibres and 40% MPD-I flocs was prepared. A dual disc cliffeiner [Jones Division of the Beloit Corporation. Dalto
Beloit Jones Model 30002 Beloit Jones Model 3000 20-inch Duplex Cliff Einer manufactured by Massachusetts 01226).
0-inch Double Disc refiner)].
The riffina plate was positioned between the rotor and stator plates with a 20 mm mil gap. The rotor plate was operated at 900 rpm. After passing through the refiner, the slurry was passed through a second refiner under the same operating conditions. After two passes through the refiner, the fibrids in the slurry were sufficiently reduced in size and fully opened into the fibrid film that the floc fibers were well distributed between the fibres. The slurry thus produced is then diluted to about 0.1 wt% solids and fed to a conventional cylinder wet papermaking machine to produce a continuous sheet of wet paper on the papermaking machine and an endless felt. The water content is adjusted by suction and pressure to about 400% based on solids (80% by weight based on wet sheet). The weight of solids in the wet paper was about 36 g / m ² . The continuous wet sheet was then fed to a forming roll where it was continuously wound onto a cylindrical tube until it overlapped about 70 times. Longitudinal cuts were then made in this layered paper, then the entire thickness of the wet lap (wet layered paper) was removed and placed between the platens of the hot press. The platen was held at 140 ° C and covered with a wire screen to facilitate moisture removal. The press is loaded with contact pressure and then the pressure is maintained at 35 kg / cm ² (3450 kPa; 5 while maintaining the platen of the press at 140 ° C.).
00 psi) and held at 35 kg / cm ² for 1 hour. The product referred to herein as a "standard pressboard" is a low density aromatic polyamide pressboard (aramid pressboar) that is about 3.2 mm (126 mil) thick.
It was d). It has a density of 0.82 g / cm ³ , a calculated void volume% Vv of 41% by volume of the pressboard, 2.13 m.
It was found to have a compression set of m (84 mils) and an oil absorption of 32.5%. Vo is 0.38 cm ³ /
g, Vml was 0.38 cm ³ / g (rounded from 0.3791), and Vmh was 0.42 cm ³ / g (0.419).
Rounded from 7), the Va for this standard pressboard sample is 0.42 cm ³ / g and the ratio Va /
Vml was 1.1.

B. Manufacture of compression resistant pressboards "Standard pressboards" manufactured as described in Part A above, 30.5 cm x 30.5 cm (12 inches x 12 cm).
Inch) square sheets are pre-dried at 150 ° C. for at least 2 hours and then flat pressed [Machine No. 9175-
M, Watson Stillman Press Davigion, Farrell, M Heart Machinery Group, 25 Main Street, Ansonia, Connecticutto 06401 (Mach
ine No. 9175-M, Watson Stillman Press Divisi
on, Farrel Company, Emhart Machinery Group, 25 M
ain St., Ansonia, Connecticut 06401)]. With a platen preheated to 280 ° C. and held at that temperature, 19.5 kg / cm ²
Total pressure of (1910 kPa; 277 psi) is 20
Apply to "standard pressboard" for minutes, release pressure for a few seconds, then add that pressure for a total of 1, 2, 3, 6, 12 and 1
After 6 minutes, it was added again to allow trapped gas to escape. After a total of 20 minutes of hot-pressing, the pressboard is taken out in a hot state, placed in another press at room temperature and just enough 2.8 kg / cm ² (276 kPa; 276 kPa; to hold the pressboard flat while cooling). 40 psi)
It was allowed to cool under pressure. The product designated "Sample 1A" was an aromatic polyamide pressboard of approximately 2.45 mm (96.5 mil) thickness (thickness range 2.35 mm-2.53 mm). It has a density of 1.11 g / cm ³ , 20
%% Vv, 0.30 mm (12 mil) compression set,
And an oil absorption of 12.71%. Vo is 0.15cm ³ / g, Vml is 0.15cm ³ /
g (rounded from 0.1502), and Vmh is 0.1
It was 7 cm ^{3 /} g (rounded from 0.1700).
The Va for sample 1A was 0.17 cm ³ / g and the ratio Va / Vml was 1.1.

Another sheet of pre-dried "standard pressboard" was added to 18.5 kg / cm ² (1813 kPa; 263).
The same process was followed except that a pressure of psi) was applied in the press at 280 ° C. for a total of 20 minutes. "Sample 1
The product named "B" is about 2.5 mm (98.7 mils)
It had a thickness (thickness range: 2.38 to 2.60 mm). It has a density of 1.08 g / cm ³ , 22 %% Vv, 0.36
It was found to have a compression set of mm (14 mils) and an oil absorption of 12.19%. Vo is 0.14 cm ³ /
g, Vml is rounded from 0.16cm ³ /g(0.1551) and Vmh is 0.17cm ³ /g(0.174
Rounded from 3). The Va for sample 1B is 0.17 cm ³ / g and the ratio Va / Vml is 1.
It was 1.

EXAMPLE 2 Two 46 cm x 122 cm (18 inches x 48 inches) made substantially as described in Part A of Example 1 but having a thickness of 3.0 mm (118 mils). Of a rectangular sheet of 1.6 mm thick "standard pressboard" 46 cm x 122 cm prepared in a similar manner except that proportionally less overlap of wet paper is wound on a cylindrical roll during the forming process. Aligned in stacks above and below the sheets. All of the sheets were pre-dried at 150 ° C just before forming the stack. The aligned stacks were then immediately placed into a hot press with a platen heated to 280 ° C (535 ° F) with oil and contact pressure at 280 ° C for a 2 minute cycle (3.5 kg / c).
m ² ) and subsequent release of pressure 3 times. 28
35 kg after 1 minute cycle and rapid release of pressure at kg / cm ² (2758 kPa; 400 psi)
1 minute cycle of pressure / cm ² followed by rapid release,
Then, hold the platen at 280 ° C for 15 minutes 35
A pressure of kg / cm ² was applied. The pressboard product is taken out hot and placed in another press under contact pressure first at room temperature and water cooled to absorb the heat of the pressboard and keep it flat during cooling. This product, designated "Sample 2", was an aromatic polyamide pressboard approximately 5.3 mm thick (210 mils). It has a density of 1.12 g / cm ³ , 19 %% Vv, 0.13 m
It was found to have a compression set of m (5 mils) and an oil absorption of 9.3%. Vo is 0.11 cm ³ / g, Vm
l is 0.09 cm ^{3 /} g (rounded from 0.0940)
And Vmh was 0.17 cm ^{3 /} g (rounded from 0.1665). Va for the sample 2 is 0.17 cm ^3.
/ G and the ratio Va / Vml were 1.8.

Example 3 A 2.1 mm thickness prepared substantially the same as the "Standard Pressboard" of Part A of Example 1 except that proportionally less overlap of wet paper was used. 46 cm x 81 cm (18 inches x 32)
Inch) rectangular sheets were placed in a press equipped with electrical heating and water cooling without predrying. First press 66 ℃
(150 ° F) and contact pressure about 3.5 kg / cm ² (345
kPa; 50 psi). Press the press at the same contact pressure for about 20 minutes at about 280 ° C (about 53
Heated to 5 ° F. Then the pressure is 35 kg / cm
² (3448 kPa; 500 psi) and held at that pressure for 12 minutes without pressure release, while holding the press at 280 ° C. The electrical heating was then discontinued, then the press was cooled to 66 ° C. by circulating cold water for 20 minutes, while the pressure was kept at 35 kg / cm ² . This product, named “Sample 3”, is approximately 1.
It was a 6 mm thick (64 mil) aromatic polyamide pressboard. It has a density of 1.13 g / cm ³ , a% Vv of 18%, a compression set of 0.13 mm (5 mils) and 9.3.
It was found to have an oil absorption of 2%. Vo is 0.
11cm ³ / g, Vml is 0.06cm ³ /g(0.055
Rounded from 3) and Vmh is 0.14 cm ³ / g
(Rounded from 0.1390). The Va for sample 3 was 0.14 cm ³ / g and the ratio Va / Vml was 2.5.

Example 4 A square sheet of low density pressboard was prepared in substantially the same manner as the "Standard Pressboard" of Part A of Example 1 with the following exceptions. The fibrid was purified and mixed with the flocks on a paper machine. Wet paper 5
Zero sheets were combined into a wet trap and the entire wet trap was cut into 20 cm (8-inch) squares. When the wet trap quadrangle was pressed at 140 ° C. under a pressure of 35 kg / cm ² , the pressure was applied for 30 minutes instead of 1 hour. The low density pressboard so formed is 2.1 mm (81 mil) thick and 0.8
It had a density of 8 g / cm ³ . The% Vv is 36%
It was. Low density pressboard in oven for 4 hours 1
It was pre-dried at 20 ° C and then placed between the platens of a flat press preheated to 280 ° C as in Part B of Example 1. A low pressure was initiated, a pressure release allowing trap gas escape, followed by a re-application of pressure over a short period of 3 cycles. 53 kg / cm ² (5171 k)
A pressure of Pa; 750 psi) was applied over a contact time of 1 minute and the hot press board was finally cooled in a separate press under restraint. The product labeled "Sample 4A" is an aromatic polyamide pressboard of 1.75 mm (69 mils) thick and had a density of 1.04 g / cm ^3. Its% Vv was 25%. Vml is 0.1
Rounded from 5cm ³ /g(0.1542), Vmh was found to be rounded from 0.17cm ³ /g(0.1712). The compression set is 0.20 mm (8.0 mil), the oil absorption is 15.9% by weight of the press board, and Vo is 0.19 cm.
^{It was 3} / g. Va is 0.19c for sample 4A.
The m ³ / g and the ratio Va / Vml were 1.2.

Another 20 cm square sheet of low density pressboard was used to weigh about 60 g / m ² of solids in the wet paper.
And the wet trap was formed from 30 sheets of moistened paper, and pressure was applied for 45 minutes instead of 30 minutes in the pressing process. The low density pressboard was 2.1 mm (84 mil) thick and had a density of 0.92 g / cm ³ . The% Vv was 33%. The low density pressboard was pre-dried and hot pressed in the same manner as sample 4A except that a pressure of 53 kg / cm ² was applied for a contact time of 10 minutes. The product designated Sample "4B" was a 71 mm thick aromatic polyamide pressboard and had a density of 1.15 g / cm ³ . Its% Vv was 17%. Vml is 0.0
It was 5 cm ^{3 /} g (rounded from 0.0486) and Vmh was 0.15 cm ^{3 /} g (rounded from 0.1452). The compression set is 0.147 mm (5.8 mil), the oil absorption is 9.7% by weight of the pressboard, and V
o was 0.11 cm ³ / g. For sample 4B,
Va was 0.15 cm ³ / g and the ratio Va / Vml was 3.0.

Example 5 In a series of experiments, low density pressboards containing varying proportions of MPD-I fibrids and flock were produced. The low density pressboard was made in substantially the same manner as the "Standard Pressboard" of Part A of Example 1 except as noted below. The fibrids were purified and then mixed with flocks on a paper machine in the proportions described below. Wet paper with a solids weight of about 60 g / m ² was produced. Thirty sheets of wet paper were combined into a wet trap, which was cut into 20 cm (8 inch) squares and pressed.

In one experiment, a mixture of 80% fibrids and 20% flock having a cut length of 0.32 cm (0.125 inch) was used. Low density pressboard at 140 ℃ for 1.5 hours 17.6kg / cm ²
It was manufactured under a pressure of (1724 kPa; 250 psi). It was approximately 2.1 mm (82 mil) thick and had a density of 0.92 g / cm ³ . % Vv is 33%
It was.

The low density pressboard was dried at 120 ° C. for 4 hours and under low pressure, first with a short cycle of pressure release and re-application, then 8.8 kg / cm ² (862 kPa;
Pressed at 280 ° C. for 10 minutes at 125 psi).
The product named “Sample 5A” is approximately 1.9 mm (7 mm
3 mil) thick aromatic polyamide pressboard,
It had a density of 1.04 g / cm ³ , a compression set of 0.21 mm (8.3 mil), an oil absorption of 13.7 wt% pressboard, and a Vo of 0.16 cm ³ / g. . Sample 5
The% Vv for A was calculated to be 25%. Vml is 0.
10 cm ^{3 /} g (rounded from 0.0990), Vmh
Also was 0.10 cm ^{3 /} g (rounded from 0.0996). Va is 0.16 cm ³ / g (V
ml, Vo and Vmh values) and the ratio Va / Vml was 1.6.

A mixture of 40% fibrids and 60% flocs was used and the pressure applied was 140 ° C. and 45%.
Minute period 35kg / cm ² (3450kPa; 500p
The method of making a low density pressboard was repeated except that it was si). Low density press board is about 2.6mm
(103 mils) thick and had a density of 0.78 g / cm ³ . % Vv was 43%. The low density pressboard is dried at 120 ° C. for 4 hours and begins with a short cycle of pressure release and re-application, then 53 kg / c.
It was pressed at 280 ° C. under a low pressure for 10 minutes at a pressure of m ³ (5171 kPa) and finally cooled under restraint with another press. The product named "Sample 5B" is about 2.0 mm
(79 mil) thick aromatic polyamide pressboard with a density of 1.02 g / cm ³ , a compression set of 0.15 mm (6.0 mils) and an oil absorption of 17.1% by weight of the pressboard. And Vo was 0.20 cm ³ / g. % Vv was 26%. Vml is 0.17 cm ³ /
g (rounded from 0.1683), Vmh is 0.27c
m ^{3 /} g (rounded from 0.2673). For sample 5B, Va was 0.27 cm ³ / g and the ratio Va / Vml was 1.6.

The method of making a low density pressboard was repeated again except that a mixture of 20% fibrids and 80% flocs was used and the pressure applied was 35 kg / cm ² at 140 ° C. for a period of 45 minutes. . The low density pressboard was about 3.1 mm (123 mil) thick and had a density of 0.70 g / cm ³ . The% Vv for this low density pressboard was 49%. The low density pressboard was dried as described above and started under low pressure with a short cycle of pressure release and reapplication, then 79 kg /
It was pressed at 280 ° C. for 10 minutes at cm ² (7763 kPa; 1125 psi). "Sample 5C" named product is an aromatic polyamide pressboard approximately 2.1 mm (84 mils) thickness, density of 1.03 g / cm ^3,
It has a compression set of 0.35 mm (13.6 mils), oil absorption of 12.1% by weight of the pressboard, and Vo of 0.3.
It was 14 cm ³ / g. % Vv was 25%. V
ml was 0.16 cm ^{3 /} g (rounded from 0.1565) and Vmh was 0.23 cm ^{3 /} g (rounded from 0.2342). Va is 0.2 with respect to the sample 5C.
It was 3 cm ³ / g and the ratio Va / Vml was 1.5.

The use of a mixture of 95% fibrids and 5% flock and the applied pressure at 140 ° C. was 1.
Except for a 5 hour period of 17.6 kg / cm ² .
The method of making a low density pressboard was repeated again. The low density pressboard was about 1.9 mm (75 mils) thick and had a density of 0.90 g / cm ³ . % V
v was 35%. The low density pressboard was dried as above and pressed at 280 ° C. under low pressure with a short cycle of initial pressure release and re-application, then 8.8 kg / cm ² for 10 minutes. "Sample 5D" named product is an aromatic polyamide pressboard approximately 1.7 mm (68 mils) thickness, density of 1.06 g / cm ^3, 0.34
mm (13.4 mil) compression set, 1 for press board
It has an oil absorption of 1.7% by weight and has a Vo of 0.14c.
It was m ³ / g. % Vv was 23%. Vml is 0.05 cm ^{3 /} g (rounded from 0.0459), V
The mh was 0.08 cm ^{3 /} g (rounded from 0.0805). Va is 0.14 cm ³ for the sample 5D.
/ G and the ratio Va / Vml was 3.0.

Example 6 In a series of experiments, low density pressboards based in part on high temperature resistant blocks other than MPD-I blocks were produced. The low density pressboard was prepared by blending a non-MPD-I block with an MPD-I block having a cut length of 0.32 cm (0.125 inch), and a blend of the block purified in the following proportions and a papermaking machine. Prepared in substantially the same manner as the "Standard Pressboard" in Part A of Example 1 except that it was mixed in. Wet paper was prepared with a solids weight of about 60 g / cm ² . Thirty sheets of wet paper were combined into a wet trap, which was cut into 20 cm (8 inch) squares and pressed under the conditions described in Example 1, Part A.

In one experiment, 60% MPD-I
Fibrids, 20% MPD-I Flock and linear density of 1.67 decitex (1.5 denier) and 0.32 cm.
Commercially available poly (p-phenylene terephthalamide) (PPD) having a cut length of (0.125 inch).
-T) 2.9 mm using 20% floc mixture
A low density pressboard having a (113 mil) thickness, a density of 0.83 cm ³ / g and a% Vv of 41% was produced. The low density pressboard was dried at 120 ° C. for 4 hours and at 280 ° C. under low pressure with a short cycle of initial pressure release and re-application, then 53 kg / cm ² (5171).
kPa; 750 psi) for 10 minutes and the hot pressboard was finally cooled in another press under restraint. The product named "Sample 6A" is 1.10 g / c
With a density of m ³ , a% Vv of 22%, a compression set of 0.27 mm (10.8 mil), an oil uptake of 10.8 wt% of the pressboard and a Vo of 0.13 cm ³ /g.2. 2 mm
It was a (86 mil) thick pressboard. Vml is 0.08 cm ^{3 /} g (rounded from 0.0787), V
The mh was 0.12 cm ^{3 /} g (rounded from 0.1151). Va of the sample 6A is 0.13 cm ³ /
g and the ratio Va / Vml was 1.6.

In another experiment, 60% MPD-I fibrids, 35% MPD-I floc and 2.4 g / c.
Using a mixture of 5% E-glass fiber flock having a density of m ³ , a linear density of 3.3 decitex (3 denier), and a cut length of 0.64 cm (0.25 inch), 2.2 mm ( A low density pressboard having a thickness of 88 mils), a density of 0.91 cm ³ / g, and a% Vv of 36% was produced. Dry low density pressboard and sample 6
Pressed by the same method described above for making A. 1.15 g / c for product named "Sample 6B"
1.8 mm with a density of m ³ , 20 %% Vv, 0.18 mm (7 mil) compression set, 8.6 wt% oil uptake of pressboard and a Vo of 0.10 cm ³ / g. 71 mil) thick aromatic polyamide / glass fiber pressboard. Vml is rounded from 0.06cm ³ /g(0.0576), Vmh is 0.14 cm ³ / g
(Rounded from 0.1424). The Va for sample 6B is 0.14 cm ³ / g and the ratio Va /
Vml was 2.5.

Control samples outside the scope of the invention (1) Pressure was 53 kg / cm ² (5171 kPa; 7
50 psi), press again at 280 ° C
The procedure of Example 1, Part B was repeated except that the temperature was held at. This product, designated "Control 1", had an oil absorption of only 2.03%. It is about 2.2m
m (87 mil) thickness (thickness range 2.14-2.31 mm)
And a density of 1.21 g / cm ³ , a% V of 12%
v and a compression set of 0.30 mm (12 mils). Vo is 0.023 cm ³ / g, Vml is 0.04c
m ^{3 /} g (rounded from 0.0433), Vmh is 0.0
Atsuta at the rounded) 09cm ³ /g(0.0889. The Va was 0.04 cm ³ / g and the ratio Va / Vml was 2.05 with respect to the control 1.

(2) A method for producing a "standard pressboard", as described in Example 1, Part A, by heating the platen of the press to 200 ° C. and loading the press with contact pressure. The pressure is 60 kg / cm ² (5880 kP
a; 850 psi), and 60 kg / c
It was held at m ² (5880 kPa; 850 psi) for 1 hour while repeating, except that the platen of the press was held at 200 ° C. The product designated "Control 2" had a high value of compression set of 1.0 mm (40 mils). It has a density of 1.07 g / cm ³ , 22 %% Vv
And had an oil absorption of 9.59%. Vo is 0.11
cm ³ / g, Vml is 0.17cm ³ /g(0.1733c
rounded from m ³ / g), Vmh is also 0.17 cm ³ / g
(Rounded down from 0.1723). Va is 0.17 cm ³ / g for control 2 and the ratio Va / V
ml was 1.0. (3A) MPD-I filaments are substantially described in U.S. Pat. Nos. 3,756,908 and 6
Produced as described by Gross in columns, lines 11-23. The resulting high modulus filaments were then cut into blocks having a length of about 0.25 inch and then slurried in water to a concentration of about 0.3%.

The MPD-I fibrides were prepared substantially as described in US Pat. No. 3,756,908, column 5, columns 34-57.
Prepared as described in the row. The purified fibrids were then further diluted in water to a concentration of about 0.5% and the high modulus flocs described above at a ratio of fibrids to flocs of about 1.55 to 1.0 (60% fibrids and 40% flocs). The slurry was passed through a mixing "T". The mixture was directed to the headbox of a Hood Linear paper machine and then to a forming wire for the production of moistened sheets. The wet sheet was then removed from the wire and passed through a steam oven dryer to reduce the sheet moisture content to about 5% or less. The paper was then rolled onto rolls for further processing. The paper was removed from the roll and cut into 20 cm (8 inch) squares, then substantially as described in US Pat.
Samples of 2-ply paper were prepared by platen pressing as described in column 7, lines 6-11 of 56,908. Two layer paper sample is 70.3kg / cm
² (689.5kPa; 1000psi) and 280 ° C
And pressed for 1 minute.

The resulting paper, designated "Control 3A", is about 0.25 mm (10 mils) thick and about 0.87 g / cm.
It had a density of ³ , a% Vv of 37% by volume of paper. Vm
1 was 0.28 cm ^{3 /} g (rounded from 0.2842) and Vm was 0.18 cm ^{3 /} g (rounded from 0.1818). Compression set is 1.0 mm (40 mil), oil absorption is 35.3% by weight of paper, Vo is 0.41c
It was m ³ / g. Va is 0.41c compared to the control 3A.
m ³ / g and the ratio Va / Vml was 1.5.

(3B) MPD-I filaments are substantially prepared according to US Pat. No. 3,756,908, column 5, column 68-
Gross at line 75 and column 6 number 1-7
To produce a low modulus filament, which was then cut into flock having a length of about 0.25 inch and submerged in water to a concentration of 0.2%. It was made into a slurry.

MPD-I fibrids were prepared as described above for Control 3A and were wet 8 cm square handsheet molds (wet 20-cm (8-i).
n) square handsheet mold) [eg Noble (Nob
le) and Wood (in the type manufactured by Wood) with a ratio of fibrids to flock of 1.5 to 1.0 (60% fibrid and 40% floc) in combination with low modulos flock. To produce paper. The paper produced in this way is considered to be essentially the same as the paper made on the Hood Linear paper machine. The wet sheet was removed from the 100 mesh screen of the hand sheet mold and dried in a hot sheet dryer to reduce the moisture content by about 5% or less. The sheet was then platen pressed to produce a two layer paper sample. They are 70.3 kg / cm ² (689.5 kPa;
Pressed at 1000 psi) and 260 ° C. for 1 minute.

The resulting paper, designated "Control 3B", is about 0.29 mm (11 mils) thick and about 0.77 g / cm.
It had a density of ³ , a% Vv of 44% by volume of paper. Vm
Is 0.58 cm ^{3 /} g (rounded from 0.5787) and Vmh is 0.38 cm ^{3 /} g (0.3793).
It was rounded off from). Compression set is 1.4 mm
(54 mil), oil absorption was 49.9% by weight of paper and Vo was 0.58 cm ³ / g. For Control 3B, Va was 0.58 cm ³ / g and the ratio Va / Vml was 1.0.

(4) A low-density press board was placed at 140 ° C. for 45 minutes for 35 kg / cm ² (3450 kPa; 50).
The method of Example 5 for making sample 5D was repeated using a mixture of 95% fibrids and 5% flock except that it was made by applying a pressure of 0 psi). This low density press board is about 1.7 mm (68
Mil) thickness and had a density of 1.00 g / cm ³ . % Vv was 28%. The low density pressboard was dried at 120 ° C. for 4 hours and pressed at 280 ° C. under low pressure, first with a short cycle of pressure release and re-application, then at 8.8 kg / cm ² for 5 minutes. The product named "Control 4" is about 1.6 mm (62 mils)
Aromatic polyamide pressboard of thickness 1.12
It had a density of g / cm ³ , a compression set of 0.14 mm (5.5 mils), an oil absorption of 1.4% by weight of the pressboard and a Vo of 0.02 cm ³ / g. % Vv is 19%
It was. Vml was rounded from 0.01cm ³ /g(0.0141), Vmh is 0.02cm ³ /g(0.01
It was rounded from 73). V against “control 4”
a was 0.02 cm ³ / g and the ratio Va / Vml was 1.2.

The properties and void parameters for all of the pressboard samples prepared as described in the examples, along with the control samples, are listed in the table. A "standard pressboard" (Pressboard abbreviated Std) sample of Part A of Example 1 is also described. In the table, the samples are listed in descending order according to their calculated void volume,% Vv.

[0070]

[Table 1]

Claims (10)

[Claims] 1. Aromatic polyamide fibrids 20-95
A high density pressboard comprising 80% by weight and 80-5% by weight of a high temperature resistant block, the pressboard having a calculated void volume of 13-28% by volume of the pressboard and 0.5.
~ 50mm thickness and 0.20 at low surface / volume
cm ³ / and g is less than the mercury intrusion volume Vml, mercury intrusion volume Vmh of 0.08-0.28Cm ³ / g at high surface / volume, expressed in cm ³ / g from .09 to 0.28
A volumetric oil absorption rate Vo and a weight oil absorption rate of 8-24% by weight, a total effective absorption volume Va expressed in cm ³ / g equal to the maximum of the values of Vml, Vmh and Vo,
A high density pressboard characterized in that the ratio of Va to ml is at least 1.1 and the pressboard has a compression set greater than 0.12 mm but not greater than 0.5 mm. 2. The high temperature resistant flock is an aromatic polyamide flock, and the pressboard is 1.0-1.2.
The pressboard according to claim 1, having a density of 0 g / cm ³ . 3. At least a portion of the block is poly (p
-Phenylene terephthalamide). 4. The press board according to claim 1, wherein at least a part of the flock is a glass fiber flock. 5. Aromatic polyamide fibrids and flocs are essentially poly (m-phenylene isophthalamide).
The pressboard according to claim 2, comprising 6. The pressboard of claim 5 wherein said pressboard comprises 50-70% by weight fibrids and 50-30% by weight flocks. 7. The press board according to claim 6, wherein the density is 1.02 to 1.17 g / cm ³ . 8. The press board according to claim 7, wherein the density is 1.10 to 1.15 g / cm ³ . 9. The pressboard of claim 6, wherein the compression set is greater than 0.12 mm but less than 0.35 mm. 10. The pressboard of claim 9, wherein the compression set is greater than 0.20 but less than 0.30 mm.