Synthetic fiber paper

Details Synthetic fiber paper Synthetic fiber paper

2000-01-20

2002-10-01

Fortuna, Jose (Department: 1731)

Paper making and fiber liberation

Processes and products

Plural fiber containing

C162S138000, C162S149000, C162S157300, C162S181600, C442S415000, C442S169000, C428S324000, C428S338000

Reexamination Certificate

active

06458244

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a synthetic fiber paper, particularly to a fiber paper made of aromatic polyamide synthetic fiber as main raw material; this invention also relates to a process for preparing the synthetic fiber paper.
DESCRIPTION OF THE PRIOR ART
The synthetic fiber paper of aromatic polyamide is a paper-like material made of synthetic fiber of aromatic polyamide as raw material through a special papermaking technology. Owing to high-temperature resistance, high strength, low-deformability, resistivity against fire, burning resistance, resistance to chemical corrosion and excellent property of insulation, it has been widely used in some high-tech areas such as mechano-electronics product, aviation, aerospace etc. At present, the fiber paper of aromatic polyamide sold on the market, trade name being called as “Nomex Brand paper”, uses the fiber of poly (m-phenylene metaphthal amide). However, there is no any satisfied process for preparing the said synthetic fiber paper has been disclosed yet.
SUMMARY OF THE INVENTION
In view of the shortage of the prior art, the object of the present invention is to provide a synthetic fiber paper made of poly (p-phenylene terephthal amide) as raw material. This fiber paper has high-temperature resistance, high strength, low-deformability, resistivity against fire, burning resistance, resistance to chemical corrosion and excellent property of insulation.
The another object of the present invention is to provide a process for preparing a synthetic fiber paper made of poly (p-phenylene terephthal amide) fiber as raw material.
The present invention provides a synthetic fiber paper comprises (parts by weight):
Poly (p-phenylene terephthal amide) fiber
50-80
Polyethylene glycol terephthalate fiber
20-50
Powdered mica
 0-50
Preferably, the above-mentioned synthetic fiber paper comprises (parts by weight):
Poly (p-phenylene terephthal amide) fiber
70-80
Polyethylene glycol terephthalate fiber
20-30
The no-stuffing synthetic fiber paper can be produced in proportion as aforesaid content.
More preferably, the above-mentioned synthetic fiber paper comprises(parts by weight):
Poly (p-phenylene terephthal amide) fiber
60-70
Polyethylene glycol terephthalate fiber
30-40
Powdered mica
 0-10
The low stuffing synthetic fiber paper can be produced in proportion as aforesaid content. Powdered mica with 5-20 &mgr;m is preferably used in present invention.
More preferably, the above-mentioned synthetic fiber paper comprises (parts by weight):
Poly (p-phenylene terephthal amide) fiber
50-60
Polyethylene glycol terephthalate fiber
40-50
Powdered mica
10-15
The high stuffing synthetic fiber paper can be produced in proportion as aforesaid content.
The said poly (p-phenylene terephthal amide) fiber is 1.5-2.0—, in size, 4-6 m/m in length. The polyethylene glycol terephthalate fiber is 1.5-2.0 —in size and 4-6 m/m in length.
The process for preparing the synthetic fiber paper comprising the following steps of compounding and pulping, papermaking shaping, dehydrating, drying preheating, prepressing, high-pressure hot-rolling, trimming, wherein the untreated poly (p-phenylene terephthal amide) fiber and the polyethylene glycol terephthalate fiber are in proportion loosened and dissociated before the step of compounding and pulping, then mixing with the treated poly (p-phenylene terephthal amide) fiber to compound and pulp.
The proportion between the said untreated poly (p-phenylene terephthal amide) fiber and the treated poly (p-phenylene terephthal amide) fiber is preferably 1:1-0.2 by weight, more preferably is 1:0.34 by weight.
In the said process, before compounding and pulping, the powdered mica should be also mixed with the processing additives to be a homogeneous material.
The said processing additives are an inorganic gel and/or polyethylene glycol oxide.
In the process of present invention, the preheating temperature is 240-250° C., the prepressing pressure is 1-2 Mpa, the temperature of high-pressure hot rolling is 255-265° C. and the linear pressure is 500-3000 N/cm.
DETAILED DESCRIPTION OF THE INVENTION
The poly (p-phenylene terephthal amide) fiber (Aromatic polyamide fiber 1414) is a structure fiber with general formula as follow:
It can be produced by a process comprising following steps: terephthalyl chloride and p-phenylene diamine as raw material, are polycondensed in NMP—Cacl
2
as solvent under low-temperature to poly (p-phenylene terephthal amide) resin, then undergoing liquid crystal spinning, being cut to length as required, or is precipitated directly to short fiber. The fiber has outstanding high strength (the highest tensile strength 200 CN/betx, shearing 0.29, elongation at rupture 3%), high modulus of elasticity (up to 67 KN/mm
2
), high hot resistance (decomposition point 500° C.), resistivity against fire, burning resistance, resistance to chemical corrosion and excellent property of insulation, therefore the synthetic fiber paper made of poly (p-phenylene terephthal amide) as a main component of structural fiber also has the above-mentioned outstanding excellent properties.
Because of insufficient binding force of the synthetic fibers, the synthetic fibers can not be papermaking shaping as a plant fiber does. Binding of the synthetic fibers depends mainly on adhesion of melted fiber. However the poly (p-phenylene terephthal amide) fiber doesn't have a distinct melting point, therefore during papermaking shaping some fiber having lower melting point present as crosslinking fiber has to be added. When the paper blank of synthetic fiber is rolled at nearly melting point of the crosslinking fiber, the soft and melted crosslinking fiber binds the unmelted poly (p-phenylene terephthal amide) fiber to form net-like material, so as to be finalized. In this invention the polyethylene glycol terephthalate fiber (polyester fiber) is used as the crosslinking fiber. Its structural formula:
The softening point of the fiber is 238-240° C., melting point is 255-260° C. The fiber has higher softening temperature than using temperature of the synthetic fiber paper 220° C., and higher strength, excellent electric insulation. That the polyethylene glycol terephthalate fiber is added properly as a crosslinking fiber doesn't drop the physical mechanical index and electric insulation of the synthetic fiber paper too much. While stuffing is used, the amount of the crosslinking fiber used in the present invention preferably increases to 40~50 parts by weight, most preferably increases to 30 parts by weight.
When the synthetic fiber paper is used in place where there are high-voltage and frequent or uninterrupted corona discharge being used, it is necessary to add and mix the powdered mica while papermaking, the ability for products resisting to corona discharge is strengthened by stuffing of powdered mica. The proportion of stuffing level depends on its uses, varying from 0 to 50 parts by weight. While the stuffing level reaches 50 parts by weight (high stuffing), the product also has the properties of mica besides the properties of original high strength and high-temperature resistance etc.
In the process for preparing the synthetic fiber paper of the present invention, in order to increase dispersion of fiber in water, while mixing and pulping, a micro-level of high viscosity material should be added to gets the pulp slurry to have some viscosity, increases the movement resistance of fiber in the pulp, delays the twining and flocculating of fiber, so as to improve dispersing and suspending of the fiber in pulp, finally achieves the aim of increasing homogeneity of the synthetic fiber paper.
The micro-level of residual viscosity increaser in the paper blank for papermaking shaping makes the fiber some adhesion, so that it makes the paper blank retain initial strength before finalizing, and will not get rupture in the process of transporting pulling apart from a foundation fabric. The process of papermaking can run smoothly.
The viscosity increaser used in this invention can be selected from a group consisting

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