EP2037039A1 - Paper comprising polybenzazole or precursor thereof - Google Patents

Paper comprising polybenzazole or precursor thereof Download PDF

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Publication number
EP2037039A1
EP2037039A1 EP07017825A EP07017825A EP2037039A1 EP 2037039 A1 EP2037039 A1 EP 2037039A1 EP 07017825 A EP07017825 A EP 07017825A EP 07017825 A EP07017825 A EP 07017825A EP 2037039 A1 EP2037039 A1 EP 2037039A1
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EP
European Patent Office
Prior art keywords
paper
pulp
polybenzazole
fibrid
formula
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP07017825A
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German (de)
French (fr)
Inventor
Mónica López Lorenzo
Anton Peter De Weijer
Richard Visser
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Teijin Aramid BV
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Teijin Aramid BV
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Filing date
Publication date
Application filed by Teijin Aramid BV filed Critical Teijin Aramid BV
Priority to EP07017825A priority Critical patent/EP2037039A1/en
Priority to EP08803525A priority patent/EP2191067B1/en
Priority to US12/674,819 priority patent/US20110083820A1/en
Priority to JP2010524454A priority patent/JP2010539341A/en
Priority to PCT/EP2008/061554 priority patent/WO2009033983A1/en
Priority to CN200880106946A priority patent/CN101802302A/en
Publication of EP2037039A1 publication Critical patent/EP2037039A1/en
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/10—Organic non-cellulose fibres
    • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/10—Organic non-cellulose fibres
    • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H13/26—Polyamides; Polyimides

Definitions

  • the invention relates to a paper comprising at least one of a fiber, pulp, fibril, floc, and fibrid containing a polybenzazole structure or a polybenzazole precursor structure. the invention further pertains to a method for making such papers and to the use thereof.
  • fiber, pulp, fibril, or fibrid having superior properties, including mechanical properties can be obtained by a process in which an optical anisotropic dope, containing a high concentration of a high molecular weight aromatic polyamide having a substituent such as a hydroxy, thiohydroxy, or amine group in an acidic solvent, is applied using a wet air gap spinning process, a jet spinning process, or any other conventional method to obtain a fiber, pulp, fibril, or fibrid, which are then heat treated.
  • an optical anisotropic dope containing a high concentration of a high molecular weight aromatic polyamide having a substituent such as a hydroxy, thiohydroxy, or amine group in an acidic solvent
  • the present invention relates to paper made from at least one of a fiber, pulp, fibril, floc, and fibrid comprising polybenzazole having a repeating unit of formula (I) and/or (II) wherein Ar 1 and Ar 2 are independently an aromatic group having 4 to 12 carbon atoms, Ar 1 and Ar 2 have the para or meta configuration, and X and Y are the same or different and selected from O, S, and NH; and wherein the paper contains less than 0.15 wt% of non-extractable phosphorus compound.
  • para and metal relate to the positions of the two amino groups or the two carbonyl groups at the aromatic ring. If Ar 2 contains more than one aromatic ring there are formally no para and meta positions, but the corresponding positions are mentioned pseudo-para and pseudo-meta positions, which are included in the definition of "para” and"meta”.
  • the present fibers, pulp, fibrils, floc, or fibrids are manufactured by a method comprising the steps of spinning or extruding a dope and solidifying it to a coagulation liquid, and then subjecting the obtained fiber as was described in EP 07008742 .
  • the invention also relates to a precursor paper, which as such has excellent properties and therefore can be used as such.
  • This precursor paper contains a polybenzazole precursor having the repeating unit expressed by formula (III): wherein Ar 1 and Ar 2 are independently an aromatic group having 4 to 12 carbon atoms, Ar 1 and Ar 2 have the para or meta configuration, X and Y are the same or different and selected from O, S, and NH, and n is 0 or 1.
  • Ar 1 examples are phenylene, naphthalenediyl, and bivalent heteroaromatic groups. Ar 1 may be substituted with hydroxy and/or halogen groups.
  • Ar 1 is preferably selected from and
  • Ar 2 is a tri- or quadrivalent aromatic group with 4-12 carbon atoms.
  • a 2 examples of A 2 are benzenetri- or tetrayl, naphthalenetri- or tetrayl, diphenyltri- or tetrayl, and tri- or quadrivalent heterocyclic group can be listed as Ar 2 .
  • Ar 2 moieties may be substituted with a hydroxy and/or halogen group.
  • Ar 2 is preferably selected from:
  • the benzene group is the most preferred Ar 2 group.
  • Ar 1 is para- or meta-phenylene: or and Ar 2 is or wherein X and Y are O, and the straight lines represent a bond.
  • the fiber may also be a copolymer containing repeating units expressed by formula (IV)
  • the Ar 1 groups have independently the previously given meanings.
  • the preferred Ar 1 is para-or meta-phenylene.
  • the polybenzazole preferably comprises 40 to 100 mole% of the repeating unit expressed by formula (I) and/or (II) with 60 to 0 mole% of the repeating unit expressed by formula (IV), to a total of 100 mole%.
  • the polybenzazole preferably comprises 60 to 100 mole% of the repeating unit expressed by formula (I) and/or (II) with 40 to 0 mole% of the repeating unit expressed by formula (IV), to a total of 100 mole%.
  • the polybenzazole which can be obtained form the polymer precursors contains imidazole, thiazole, and/or oxazole rings.
  • polybenzazole precursor containing one of the following repeating units is especially preferred. or or or or or or
  • PBO paper is known in the art, i.e. as mentioned in patent US 6890636 , such paper inherently contains substantial amounts of phosphoric acid which was used as spin dope for making fiber, and which cannot completely be removed.
  • the PBO paper of this invention contains less than 0.15 wt% of non-extractable phosphorus compound (i.e. mainly phosphoric acid), preferably much less such as less than 30 ppm, and most preferably none or virtually none of phosphorus compound (when the spin dope does not contain any phosphoric acid).
  • the unique method for making the PBO paper of this invention resides in a method wherein the ring-closed PBO structure is obtained from an open precursor structure still having OH, SH, or NH 2 groups. These hydrophilic groups allow the precursor to dissolve in hydrophilic solvents such as water, alcohol, water-alcohol mixtures, and the like.
  • PBO paper having less than 0.15 wt% phosphorus compound is unknown.
  • the known PBO papers have been made from PBO-polyphosphorus acid-containing spin dopes, leading to paper having (much) more than 0.15 wt% non-extractable phosphorus.
  • small amounts of phosphorus acid or other phosphorus compounds can be added to the spin dope, leading to papers having minor amounts (i.e. less than 0.15 wt%) of phosphorus.
  • the amount of phosphorus present in the paper can easily be measured by using standard methods such as by spectroscopy or titration.
  • the papers of this invention may include combinations of fiber, pulp, fibril, floc or fibrid, such as fibrids and floc.
  • the papers of the invention can be made by conventional papermaking processes, which processes allow adding common additives and auxiliary materials to the material for making paper, such as pigments, binders, silicates, fillers, and other additives.
  • the paper such obtained may be processed further such as by applying known calendaring methods to further enhance the density of the paper.
  • fibrids refers to non-granular film-like particles.
  • the fibrids have an average length of 0.2 to 1 mm with a length-to-width aspect ratio of 5:1 to 10:1.
  • the thickness dimension is on the order of a fraction of a micron.
  • Such fibrids when fresh, are used wet and are deposited as a binder physically entwined about the floc component of the paper. Fresh fibrids and previously-dried fibrids can be used in paper of this invention.
  • the term "floc" refers to short fibers, typically having a length of 2 to 12 mm and a linear density of 1-10 decitex.
  • the floc can be fresh or it can be previously-dried. If fresh, it has not before been used in any product.
  • Paper pulp may comprise floc and fibrids, generally, in amounts of about 50-60%, by weight, fibrids and 40-50%, by weight, floc. Even after comminution and milling, the floc in aramid paper pulp is bound, to some extent, by the fibrids.
  • the fibrids being in a dried state, are bound together or collapsed and less useful as binder material than the fresh, never-dried, fibrids; but, due to their random, rigid, irregular, shape, contribute an increased porosity to the final paper structure.
  • those fibrid and floc components taken from dried papers may be called previously-dried fibrids and previously-dried floc.
  • Dried paper sheets containing polybenzazole precursor can also be processed through a high speed milling machine, such as a turbulent air grinding mill known as a Turbomill or an Ultra-Rotor, and then wet refined.
  • Turbulent air grinding mills are preferred for comminuting papers which have been calendered; but the grinding mills result in slightly shortened fiber lengths. Paper of this invention using paper pulp with shortened fiber lengths exhibits slightly reduced wet strength and a tendency to worsen paper machine continuity.
  • the paper made from the polybenzazole precursor material can be used as such. It has excellent properties as will further be demonstrated in the experimental part. However, the properties of this paper can easily be changed or improved by functionalizing at least part of the free XH and YH groups, such as OH groups. These free groups are able to react with monomers and polymers having reactive groups, such as esters, isocyanates, epoxides, and other functionalizing agents to give a covalent bond between X and/or Y and the functionalizing agent. If part of the free XH and YH groups is functionalized these papers can also be heat treated to convert the polymer precursor by a cyclizing process to ring-closed PBO polymers, thereby obtaining functionalized PBO paper.
  • the PBO obtained can also be free of phosphorus compounds. It is a further advantage that it is no longer required to make the paper from almost insoluble PBO polymers, but the papermaking process can be performed with readily soluble polymer precursors, and conversion to PBO takes place after formation of the paper.
  • the papers from this invention exhibit lower porosity than PPTA papers making them very suitable for electrical applications such as in electrical insulation material.
  • the papers are further suitable for application in honeycomb structures and in constructive materials.
  • the papers of the present invention both for PBO precursor-containing papers and PBO papers, have a much higher strength than known papers, as shown by EAB (elongation at break) and TI (tenacity index) data.
  • EAB elongation at break
  • TI tenacity index
  • the present papers are superior to PPTA paper and even to Nomex®, which is considered the strongest paper known until now.
  • the extreme strength of the present papers makes it possible to produce extreme thin papers.
  • the papers of this invention also have superior heat stability compared to PPTA paper and Nomex®.
  • the first sample had a polymer concentration of 7.4%
  • the second sample (after dilution with NMP) had a concentration of 5%
  • the final product had a polymer concentration of 4%.
  • the relative viscosity of the reaction product was 3.43.
  • the polymerization procedure for the second batch was similar, except that after 60 minutes a sample was taken and 4.0 L of NMP were added. The mixture was stirred for 30 min and then emptied. By applying this procedure, the first sample had a polymer concentration of 7.4% and the final product had a polymer concentration of 4%. The relative viscosity of the reaction product was 3.06.
  • the polymerization batches were mixed prior to spinning.
  • Polymerization of PPTA para-phenyleneterephthalamide was carried out using a 160 L Drais reactor. After sufficiently drying the reactor, 64 L of NMP/CaCl 2 with a CaCl 2 concentration of 2.5 wt% were added to the reactor. Subsequently, 1522 g of PPD were added and dissolved at room temperature. Thereafter the PPD solution was cooled to 5 °C and 2824 g of TDC were added. After addition of the TDC the polymerization reaction was continued for 45 min. Then the polymer solution was neutralized with a calcium oxide/NMP-slurry (780 g of CaO in NMP). After addition of the CaO-slurry the polymer solution was stirred for another 30 min.
  • This neutralization was carried out to remove the hydrochloric acid (HCl), which is formed during polymerization.
  • a gel-like polymer solution was obtained with a PPTA content of 4.5 wt% and having a relative viscosity of 3.0 (in 0.25% H 2 SO 4 ).
  • This product has an etarel ( ⁇ rel ) of 2.4 and a polymer concentration of 3.6% and was used to spin fibrids as well as pulp. Water was used as coagulant.
  • Example 1 and Comparative Example 1 were spun through a jet spinning nozzle (spinning hole 500 ⁇ m) at 20 Uh. Water was added through a ring-shaped channel flowing perpendicular to the polymer flow. During spinning the polymer flow was kept constant while the coagulant pressure was changed for the different samples in order to vary the SR (°SR) of the product.
  • SR °SR
  • Example 1 and Comparative Example 1 were spun into pulp through a 1 hole jet spinning nozzle (spinning hole 350 ⁇ m). The solution was spun into a zone of lower pressure. An air jet was separately applied perpendicularly to the polymer stream through ring-shaped channels to the same zone were expansion of air occurred. Thereafter, the pulp was coagulated with water in the same zone by means of applying a coagulant jet through ring-shaped channels under an angle in the direction of the polymer stream.
  • Table 2 Properties of paper samples from fibrid Paper Grammage Calliper Density EAB TI Sample (g/m 2 ) (mm) (g/cm 3 ) (%) (Nm/g) B1 99 0.168 0.59 4.3 85.2 B2 50 0.115 0.44 3.6 75.3 B3 29 0.073 0.39 3.7 72 B4 16 0.058 0.28 2.5 41.6 D1 110 0.284 0.39 1.7 28.3 D2 52 0.193 0.27 1.7 19 D3 31 0.131 0.23 1.1 14.1 D4 16 0.092 0.17 1.6 8.1
  • TGA experiments were carried out by means of a Setaram TGA/DSC 111, under nitrogen gas.
  • the paper samples were first cut into pieces and then put in Platinum (open) cells.
  • the sample weight that was used was between 10 and 20 mg.
  • the samples were heated from 20 °C to 700 °C.
  • the decomposition temperature Td 5% is the temperature at which 5% weight loss based on TGA thermogram is obtained under these conditions.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Paper (AREA)
  • Artificial Filaments (AREA)
  • Organic Insulating Materials (AREA)

Abstract

The invention relates to a paper comprising at least one of a fiber, pulp, fibril, floc, and fibrid containing a polybenzazole structure with a repeating unit of formula (I) and/or (II), or (III):
Figure imga0001
Figure imga0002
Figure imga0003
 wherein Ar1 and Ar2 are independently an aromatic group having 4 to 12 carbon atoms, Ar1 and Ar2 have the para or meta configuration, and X and Y are the same or different and selected from O, S, and NH; n is 0 or 1. The paper can be made free of non-extractable phosphorus compound. The paper is particularly suitable for making an electrical insulation material, a honeycomb structure, or a constructive material.

Description

  • The invention relates to a paper comprising at least one of a fiber, pulp, fibril, floc, and fibrid containing a polybenzazole structure or a polybenzazole precursor structure. the invention further pertains to a method for making such papers and to the use thereof.
  • It has described in EP 07008742 that fiber, pulp, fibril, or fibrid having superior properties, including mechanical properties, can be obtained by a process in which an optical anisotropic dope, containing a high concentration of a high molecular weight aromatic polyamide having a substituent such as a hydroxy, thiohydroxy, or amine group in an acidic solvent, is applied using a wet air gap spinning process, a jet spinning process, or any other conventional method to obtain a fiber, pulp, fibril, or fibrid, which are then heat treated.
  • The present invention relates to paper made from at least one of a fiber, pulp, fibril, floc, and fibrid comprising polybenzazole having a repeating unit of formula (I) and/or (II)
    Figure imgb0001
    Figure imgb0002
     wherein Ar1 and Ar2 are independently an aromatic group having 4 to 12 carbon atoms, Ar1 and Ar2 have the para or meta configuration, and X and Y are the same or different and selected from O, S, and NH; and wherein the paper contains less than 0.15 wt% of non-extractable phosphorus compound.
  • The terms "para" and"meta" relate to the positions of the two amino groups or the two carbonyl groups at the aromatic ring. If Ar2 contains more than one aromatic ring there are formally no para and meta positions, but the corresponding positions are mentioned pseudo-para and pseudo-meta positions, which are included in the definition of "para" and"meta".
  • The present fibers, pulp, fibrils, floc, or fibrids are manufactured by a method comprising the steps of spinning or extruding a dope and solidifying it to a coagulation liquid, and then subjecting the obtained fiber as was described in EP 07008742 .
  • The invention also relates to a precursor paper, which as such has excellent properties and therefore can be used as such. This precursor paper contains a polybenzazole precursor having the repeating unit expressed by formula (III):
    Figure imgb0003
     wherein Ar1 and Ar2 are independently an aromatic group having 4 to 12 carbon atoms, Ar1 and Ar2 have the para or meta configuration, X and Y are the same or different and selected from O, S, and NH, and n is 0 or 1.
  • Examples of Ar1 are phenylene, naphthalenediyl, and bivalent heteroaromatic groups. Ar1 may be substituted with hydroxy and/or halogen groups.
  • Ar1 is preferably selected from
    Figure imgb0004
     and
    Figure imgb0005
  • Ar2 is a tri- or quadrivalent aromatic group with 4-12 carbon atoms. Examples of A2 are benzenetri- or tetrayl, naphthalenetri- or tetrayl, diphenyltri- or tetrayl, and tri- or quadrivalent heterocyclic group can be listed as Ar2. These Ar2 moieties may be substituted with a hydroxy and/or halogen group.
  • Ar2 is preferably selected from:
    Figure imgb0006
     and
    Figure imgb0007
  • The benzene group is the most preferred Ar2 group.
  • In a preferred embodiment Ar1 is para- or meta-phenylene:
    Figure imgb0008
     or
    Figure imgb0009
     and Ar2 is
    Figure imgb0010
     or
    Figure imgb0011
     wherein X and Y are O, and the straight lines represent a bond.
  • In addition to the above polybenzazole the fiber may also be a copolymer containing repeating units expressed by formula (IV)
    Figure imgb0012
  • In formula (III), the Ar1 groups have independently the previously given meanings. The preferred Ar1 is para-or meta-phenylene.
  • The polybenzazole preferably comprises 40 to 100 mole% of the repeating unit expressed by formula (I) and/or (II) with 60 to 0 mole% of the repeating unit expressed by formula (IV), to a total of 100 mole%.
  • The polybenzazole preferably comprises 60 to 100 mole% of the repeating unit expressed by formula (I) and/or (II) with 40 to 0 mole% of the repeating unit expressed by formula (IV), to a total of 100 mole%.
  • Since X is an oxygen atom (-O-), sulfur atom (-S-), or imino group (-NH-), the polybenzazole which can be obtained form the polymer precursors contains imidazole, thiazole, and/or oxazole rings.
  • The polybenzazole precursor containing one of the following repeating units is especially preferred.
    Figure imgb0013
     or
    Figure imgb0014
     or
    Figure imgb0015
     or
    Figure imgb0016
     or
    Figure imgb0017
     or
    Figure imgb0018
  • Methods for making these polymers, and for making fiber, pulp, fibril, floc or fibrid thereof are disclosed in European patent application no. EP 07008742 , which is incorporated by reference.
  • Although PBO paper is known in the art, i.e. as mentioned in patent US 6890636 , such paper inherently contains substantial amounts of phosphoric acid which was used as spin dope for making fiber, and which cannot completely be removed. The PBO paper of this invention contains less than 0.15 wt% of non-extractable phosphorus compound (i.e. mainly phosphoric acid), preferably much less such as less than 30 ppm, and most preferably none or virtually none of phosphorus compound (when the spin dope does not contain any phosphoric acid). Because it is known that traces of phosphoric acid may decompose PBO fibrous materials, leading to substantial loss of paper strength, it may is utmost importance to make PBO paper that is free or at least substantially free of phosphoric acid, if such paper should maintain its strengths for long periods. The unique method for making the PBO paper of this invention resides in a method wherein the ring-closed PBO structure is obtained from an open precursor structure still having OH, SH, or NH2 groups. These hydrophilic groups allow the precursor to dissolve in hydrophilic solvents such as water, alcohol, water-alcohol mixtures, and the like.
  • Whereas PBO can practically only be dissolved in phosphoric acid-containing spin dopes, the present precursors can form spin dopes in said hydrophilic solvents, without using any phosphoric acid. Such spin dopes will lead to fiber, pulp, fibril, floc or fibrid that is completely or virtually free from phosphorus compound. PBO paper having less than 0.15 wt% phosphorus compound is unknown. The known PBO papers have been made from PBO-polyphosphorus acid-containing spin dopes, leading to paper having (much) more than 0.15 wt% non-extractable phosphorus. Although it is usually not preferred, small amounts of phosphorus acid or other phosphorus compounds can be added to the spin dope, leading to papers having minor amounts (i.e. less than 0.15 wt%) of phosphorus. The amount of phosphorus present in the paper can easily be measured by using standard methods such as by spectroscopy or titration.
  • The papers of this invention may include combinations of fiber, pulp, fibril, floc or fibrid, such as fibrids and floc. The papers of the invention can be made by conventional papermaking processes, which processes allow adding common additives and auxiliary materials to the material for making paper, such as pigments, binders, silicates, fillers, and other additives. The paper such obtained may be processed further such as by applying known calendaring methods to further enhance the density of the paper.
  • The term "fibrids" refers to non-granular film-like particles. The fibrids have an average length of 0.2 to 1 mm with a length-to-width aspect ratio of 5:1 to 10:1. The thickness dimension is on the order of a fraction of a micron. Such fibrids, when fresh, are used wet and are deposited as a binder physically entwined about the floc component of the paper. Fresh fibrids and previously-dried fibrids can be used in paper of this invention.
  • The term "floc" refers to short fibers, typically having a length of 2 to 12 mm and a linear density of 1-10 decitex. The floc can be fresh or it can be previously-dried. If fresh, it has not before been used in any product.
  • Paper pulp may comprise floc and fibrids, generally, in amounts of about 50-60%, by weight, fibrids and 40-50%, by weight, floc. Even after comminution and milling, the floc in aramid paper pulp is bound, to some extent, by the fibrids. The fibrids, being in a dried state, are bound together or collapsed and less useful as binder material than the fresh, never-dried, fibrids; but, due to their random, rigid, irregular, shape, contribute an increased porosity to the final paper structure. For purposes of this invention, those fibrid and floc components taken from dried papers may be called previously-dried fibrids and previously-dried floc.
  • Dried paper sheets containing polybenzazole precursor can also be processed through a high speed milling machine, such as a turbulent air grinding mill known as a Turbomill or an Ultra-Rotor, and then wet refined. Turbulent air grinding mills are preferred for comminuting papers which have been calendered; but the grinding mills result in slightly shortened fiber lengths. Paper of this invention using paper pulp with shortened fiber lengths exhibits slightly reduced wet strength and a tendency to worsen paper machine continuity.
  • The paper made from the polybenzazole precursor material can be used as such. It has excellent properties as will further be demonstrated in the experimental part. However, the properties of this paper can easily be changed or improved by functionalizing at least part of the free XH and YH groups, such as OH groups. These free groups are able to react with monomers and polymers having reactive groups, such as esters, isocyanates, epoxides, and other functionalizing agents to give a covalent bond between X and/or Y and the functionalizing agent. If part of the free XH and YH groups is functionalized these papers can also be heat treated to convert the polymer precursor by a cyclizing process to ring-closed PBO polymers, thereby obtaining functionalized PBO paper. Because the polymer precursor has been synthesized and spun from solutions that may be free from phosphorus compounds, the PBO obtained can also be free of phosphorus compounds. It is a further advantage that it is no longer required to make the paper from almost insoluble PBO polymers, but the papermaking process can be performed with readily soluble polymer precursors, and conversion to PBO takes place after formation of the paper.
  • In general the papers from this invention exhibit lower porosity than PPTA papers making them very suitable for electrical applications such as in electrical insulation material. The papers are further suitable for application in honeycomb structures and in constructive materials.
  • The papers of the present invention, both for PBO precursor-containing papers and PBO papers, have a much higher strength than known papers, as shown by EAB (elongation at break) and TI (tenacity index) data. For instance, the present papers are superior to PPTA paper and even to Nomex®, which is considered the strongest paper known until now.
  • The extreme strength of the present papers makes it possible to produce extreme thin papers. The papers of this invention also have superior heat stability compared to PPTA paper and Nomex®.
  • Because of the unusual strength of the present papers, papers having a grammage between 1 and 16 g/m2 can be made. The term "grammage" is a metric measure of paper weight based on the same square meter sheet of paper, regardless of paper grade.
  • The present invention will be explained more specifically by the following embodiments. However, the present invention is not limited to these embodiments.
    • General:
  • These results were obtained with the polymer precursor having the following repeating unit:
    Figure imgb0019
     and with the corresponding ring closed polymer having the repeating unit:
    Figure imgb0020
     wherein Ar1 = para-phenylene and Ar2 = diphenylene
  • Abbreviations:
    • NMP = N-metylpyrrolidone
    • DHB = dihydroxybenzidine (4,4'-diamino-3,3'-dihydroxydiphenyl)
    • TDC = terephthaloyl dichloride
    • PPD = para-phenylenediamine
    • PPTA = para-phenyleneterephthalamide
    Example 1 Polymerization to polybenzoxazole precursor
  • 2.25 L of NMP/CaCl2 and 1.75 L of NMP together with pre-dried DHB (140 °C, vacuum, 24 h) were charged into a 10 L Drais reactor and stirred for 30 minutes to let the DHB dissolve. After cooling to 5 °C, TDC was added while continuously stirring (250 rpm). After 50 minutes a sample was taken, 1.8 L of NMP were added. The mixture was stirred for 30 min, another sample was taken and again 1.8 L of NMP were added. The mixture was stirred for 30 min and the reactor was emptied through a bottom valve. By applying this procedure, the first sample had a polymer concentration of 7.4%, the second sample (after dilution with NMP) had a concentration of 5% and the final product had a polymer concentration of 4%. The relative viscosity of the reaction product was 3.43.
  • The polymerization procedure for the second batch was similar, except that after 60 minutes a sample was taken and 4.0 L of NMP were added. The mixture was stirred for 30 min and then emptied. By applying this procedure, the first sample had a polymer concentration of 7.4% and the final product had a polymer concentration of 4%. The relative viscosity of the reaction product was 3.06.
  • The polymerization batches were mixed prior to spinning.
    • Comparative example 1
  • Polymerization of PPTA para-phenyleneterephthalamide was carried out using a 160 L Drais reactor. After sufficiently drying the reactor, 64 L of NMP/CaCl2 with a CaCl2 concentration of 2.5 wt% were added to the reactor. Subsequently, 1522 g of PPD were added and dissolved at room temperature. Thereafter the PPD solution was cooled to 5 °C and 2824 g of TDC were added. After addition of the TDC the polymerization reaction was continued for 45 min. Then the polymer solution was neutralized with a calcium oxide/NMP-slurry (780 g of CaO in NMP). After addition of the CaO-slurry the polymer solution was stirred for another 30 min. This neutralization was carried out to remove the hydrochloric acid (HCl), which is formed during polymerization. A gel-like polymer solution was obtained with a PPTA content of 4.5 wt% and having a relative viscosity of 3.0 (in 0.25% H2SO4). This product has an etarel (ηrel) of 2.4 and a polymer concentration of 3.6% and was used to spin fibrids as well as pulp. Water was used as coagulant.
    • Example 2 Fibrid and pulp making
  • The solutions of Example 1 and Comparative Example 1 were spun through a jet spinning nozzle (spinning hole 500 µm) at 20 Uh. Water was added through a ring-shaped channel flowing perpendicular to the polymer flow. During spinning the polymer flow was kept constant while the coagulant pressure was changed for the different samples in order to vary the SR (°SR) of the product.
    • Pulp spinning
  • The solutions of Example 1 and Comparative Example 1 were spun into pulp through a 1 hole jet spinning nozzle (spinning hole 350 µm). The solution was spun into a zone of lower pressure. An air jet was separately applied perpendicularly to the polymer stream through ring-shaped channels to the same zone were expansion of air occurred. Thereafter, the pulp was coagulated with water in the same zone by means of applying a coagulant jet through ring-shaped channels under an angle in the direction of the polymer stream.
  • To spin the pulp with different SR values (°SR) the air pressure was kept constant while the polymer flow was varied. After spinning all samples were washed with water.
  • The process and property data of fibrids and pulp obtained in Example 2 are given in Table 1: Table 1
    Process parameters Properties
    Sampl e Polymer solution Product type Polymer solution Flow (Uh) Coagulant pressure (bar) Coagulant flow (Uh) Airflow (Nm3/h) LL0.25 Fines(%) SR Value (°SR) SSA (m2/g) Dry Solids (%)
    A Example1 pulp 6 50 12 0.58 43.3 63 0.6 5.3
    B Example1 fibrid 20 50 0.72 25 67 0.5 7.3
    C CompEx1 fibrid 20 30 0.84 25 42 2.2 5.6
    D CompEx1 fibrid 20 50 0.74 26.3 65 2.6 4.8
    E CompEx1 pulp 6 50 12 0.55 49.9 68 5.6 7.5
    F CompEx1 pulp 18 50 12 0.62 42.7 46 3.9 6.9
    • Example 3 Paper making from fibrids
  • Handsheets from 100% fibrids of samples A1 and B1-B4 and comparative examples D1-D4 and E1 with different grammage were made on a Rapid Kothen machine. The dewatered sheets were dried between two blotting papers under vacuum (95 °C, -1000 mbar, 20 min). Paper data are given in Table 2.
  • Notice the lower calliper (paper thickness) and higher densities for the papers of the invention in comparison to the reference papers. TI (Tensile Index) is 3-5 times as high for the papers of the invention than for the pulp-based reference papers when compared at the same grammage. EAB is also higher for the papers of the invention. Table 2: Properties of paper samples from fibrid
    Paper Grammage Calliper Density EAB TI
    Sample (g/m2) (mm) (g/cm3) (%) (Nm/g)
    B1 99 0.168 0.59 4.3 85.2
    B2 50 0.115 0.44 3.6 75.3
    B3 29 0.073 0.39 3.7 72
    B4 16 0.058 0.28 2.5 41.6
    D1 110 0.284 0.39 1.7 28.3
    D2 52 0.193 0.27 1.7 19
    D3 31 0.131 0.23 1.1 14.1
    D4 16 0.092 0.17 1.6 8.1
    • Example 4 Paper making from pulp
  • Handsheets from 100% pulp of samples A and E with a grammage of around 100 g/m2 were made on a Rapid Kothen machine using the same procedure as Example 3. Paper data are given in Table 3. Table 3: Properties of paper samples from pulp
    Paper Grammage Calliper Density EAB TI
    Sample (g/m2) (mm) (g/cm3) (%) (Nm/g)
    A1 110 0.265 0.415 1.5 18.8
    E1 117 0.296 0.395 1.05 9.5
    • Example 5 Heat treatment of papers
  • To convert the above polybenzazole precursor paper to the polybenzazole paper a heat treatment was performed under an inert atmosphere The procedure was as follows: The samples were enclosed in an oven under an nitrogen flow and heated with a heating rate of 10 °C/min. When the temperature of 440 °C was reached the samples were immediately taken out of the oven. Property data of the samples before and after heat treatment are given in Table 4. IR spectra of the samples were recorded on the Varian FTS-575c Infrared spectrometer equipped with the Thunderdome ATR accessory. The spectra confirmed conversion to a polybenzoxazole paper with a conversion factor >0.95.
  • TGA experiments were carried out by means of a Setaram TGA/DSC 111, under nitrogen gas. The paper samples were first cut into pieces and then put in Platinum (open) cells. The sample weight that was used was between 10 and 20 mg. The samples were heated from 20 °C to 700 °C. The decomposition temperature Td5% is the temperature at which 5% weight loss based on TGA thermogram is obtained under these conditions.
    Paper Heat Grammage Calliper Density EAB TI Td5%
    Sample Type Treated (g/m2) (mm) (g/cm3) (%) (Nm/g) °C
    B5 fibrid paper No 102.2 0.181 0.56 3 70 630
    B6 fibrid paper Yes 99.8 0.151 0.66 3.6 80 625
    A1 pulp paper No 110 0.265 0.42 1.5 18.8 630
    A2 pulp paper Yes 118 0.207 0.57 1.8 16.8 625
    D2 fibrid paper No 540
    D3 fibrid paper Yes

Claims (9)

  1. A paper comprising at least one of a fiber, pulp, fibril, floc, and fibrid containing a polybenzazole structure with a repeating unit of formula (I) and/or (II)
    Figure imgb0021
    Figure imgb0022
     wherein Ar1 and Ar2 are independently an aromatic group having 4 to 12 carbon atoms, Ar1 and Ar2 have the para or meta configuration, and X and Y are the same or different and selected from O, S, and NH; and wherein the paper contains less than 0.15 wt% of non-extractable phosphorus compound.
  2. A paper comprising at least one of fiber, pulp, fibril, floc, and fibrid having a polybenzazole precursor structure containing the repeating unit expressed by formula (III):
    Figure imgb0023
     wherein Ar1 and Ar2 are independently an aromatic group having 4 to 12 carbon atoms, Ar1 and Ar2 have the para or meta configuration, X and Y are the same or different and selected from O, S, and NH, and n is 0 or 1.
  3. The paper of claim 2 wherein at least part of XH and/or YH is functionalized.
  4. The paper of any one of claims 1-3 having a grammage from 1 to 16 g/m2.
  5. The paper of any one of claims 1-4 comprising a mixture of at least one of fiber, pulp, fibril, floc, and fibrid containing a polybenzazole structure of formula (I) and/or (II) or a polybenzazole precursor structure of formula (III), and PPTA fibrid.
  6. A method for making the paper of claim 1 comprising heating the paper of claim 2 or 3 under an inert atmosphere at a temperature allowing cyclization of the polybenzazole precursor having formula (III) to the polybenzazole comprising the structure of formula (I) and/or (II).
  7. A method for making the paper of claim 2 or 3 comprising applying a conventional papermaking process using at least one of fiber, pulp, fibril, floc, and fibrid having the polybenzazole precursor structure IV, optionally followed by one or more of a calendering step, heating step, drying step, and functionalization step.
  8. An electrical insulation material comprising the paper of any one of claims 1-5.
  9. Use of the paper of any one of claims 1-5 for making an electrical insulation material, a honeycomb structure, or a constructive material.
EP07017825A 2007-09-12 2007-09-12 Paper comprising polybenzazole or precursor thereof Withdrawn EP2037039A1 (en)

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EP07017825A EP2037039A1 (en) 2007-09-12 2007-09-12 Paper comprising polybenzazole or precursor thereof
EP08803525A EP2191067B1 (en) 2007-09-12 2008-09-02 Paper comprising polybenzazole or precursor thereof
US12/674,819 US20110083820A1 (en) 2007-09-12 2008-09-02 Paper comprising polybenzazole or precursor thereof
JP2010524454A JP2010539341A (en) 2007-09-12 2008-09-02 Paper containing polybenzazole or its precursor
PCT/EP2008/061554 WO2009033983A1 (en) 2007-09-12 2008-09-02 Paper comprising polybenzazole or precursor thereof
CN200880106946A CN101802302A (en) 2007-09-12 2008-09-02 Paper comprising polybenzazole or precursor thereof

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JP6424518B2 (en) * 2014-09-01 2018-11-21 東洋紡株式会社 Polybenzazole pulp
CN114790664B (en) * 2021-01-26 2023-02-24 中国科学院化学研究所 High-strength polyphenylene benzobisoxazole paper base material

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WO2009033983A1 (en) 2009-03-19
US20110083820A1 (en) 2011-04-14

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