DE2261619B2 - Non-woven fiber fleece with a heat-resistant binder - Google Patents

Description

/ CO _n
- NH-Q — NR — CO— (I)

in which Q is a divalent radical which contains at least one benzene ring, and R is one represents trivalent aromatic radical.

4. Nonwoven fiber fleece according to one of the «> claims 1 to 3, characterized in that the polyamide-imide has a reduced viscosity between 30 and 180 cmVg (measured in ^{0.5 l} / o solution in N-methylpyrrolidone).

5. Nonwoven fiber fleece according to claim 3, characterized in that the polymer of Formula I is the reaction product of trimellitic anhydride with 4,4'-diisocyanatodiphenyl ether.

6. Non-woven fiber web according to claim 3, characterized in that the polymers of the formula I w is the reaction product of trimellitic anhydride mit4,4'-diisocyanatodiphenylmethane.

The present invention relates to new nonwoven fibrous webs, the fibers of which are interconnected by a synthetic polymer are bound.

There is an extensive literature relating to the manufacture of nonwoven nonwovens below Use of a polymeric binder exists, these publications reflect the nature of the used Fibers, the nature of the binder or even processes and devices used in the manufacture of allow nonwoven products to affect. Depending on the intended application, one uses vegetable fibers (wood, flax, jute, hemp, sisal, Coconut, kapok, ramie), filaments of animal origin (Wool, goat hair, camel hair, rabbit hair), fibers made from artificial polymers (cellulose acetate) or synthetic polymers (polyester, polyamide, polyacrylonitrile) or glass fibers or asbestos fibers. There are also natural binders (cellulose, natural rubber) or synthetic binders (Butadiene-acrylonitrile copolymers, polyvinyl acetate, acrylic or methacrylic copolymers, polyvinyl chloride, Polychloroprene, melamine-formaldehyde resins, urine

65

material formaldehyde resins, epoxy resins)

The present invention relates to a new category of nonwoven fibrous webs, in particular to are intended for applications that require a high level of heat resistance.

The fiber webs according to the invention, the fibers of which are interconnected by a synthetic polymer are bound are characterized in that

a) the material forming the fibers is infusible or has a melting point above 180 ° C and

b) the binder is a polyamide-imide, the proportion by weight of which is 5 to 150% by weight of the dry fibers used

The polyamide-imides used as binders in the invention can be defined as products which is a number of groupings of the formula

/ CO _x

- NH-Q — N R — CO— (I)

^X7

4 ″) , in which Q denotes a divalent radical with at least one benzene ring and R represents a trivalent aromatic radical.

Examples of radicals represented by Q include the m-phenylene, p-phenylene and ρ, ρ'-diphenylene radicals or radicals of the formula

/ X

(ii)

in which T represents a divalent atom or a divalent group such as —O—, —CH2—, —C (CH ₃ ) ₂ -, —SO ₂ - or -N = N-, name.

Examples of radicals represented by R can be the trivalent radicals of the formulas

co

50

to name.

The polyamide-imides described above can be produced by various techniques, such as for example those in British Patents 5,70,858 and 1,181,446, US Pat. No. 3,260,691 and French patents 13 86617, 14 73 600, 15 01 198, 15 59 357 and 15 76 844. In the US-PS is the use of the polymers described there as adhesives and for Manufacture of fibers and molded articles specified. In FR-PS 13 86 617 and 15 01 198 is the Impregnation of glass fabrics with the described polyimides mentioned. So it's the one Impregnation of products that have already been manufactured, such as a fabric, in order to protect it

reinforce them or then process them into laminates. The present invention is is about the production of the fiber structure as such in the form of a non-woven fiber fleece, which is his can maintain interesting mechanical properties over a wide temperature range.

Among these polyamide-imides there may be mentioned in particular those made from trimellitic anhydride and a difunctional derivative of the formula

X-Q-X

(III)

ιυ

in which the symbol X denotes an NCO group or a group of the formula - NHCORi, where the Symbol Ri is an alkyl radical with 1 to 6 carbon atoms 1 <-, men or a phenyl or methylphenyl radical can be obtained.

According to the invention, preference is given to using polyamide-imides which have a reduced viscosity between 30 and 180 cm ³ / g (measured in solution with 0.5% in N-methylpyrrolidone) .

The diisocyanato-diphenylether 4,4'-derived Polytrimellithamidimide from the reaction of trimellitic acid anhydride with 4,4'-diisocyanatodiphenylmethane or particularly suitable for the preparation of the 2 ^r i nonwoven fibrous batts of this invention.

The fibers used in the invention can be selected from various fibers having the properties set out above. More specifically, it can be inorganic fibers such as _J0, for example, glass fibers, carbon fibers, aluminum and zirconium oxide fibers, asbestos fibers, boron fibers and metallic fibers, for example copper fibers and steel fibers. It can also be fibers derived from organic polymers. As _s -, Examples of such polymers can be the polyester of the PolyäthylenglykoJterephthalat type, the polyamides obtained by polycondensation of caprolactam or by reaction of adipic acid with hexamethylenediamine, polyacrylonitrile, fluorinated polymers such as polytetrafluoroethylene or copolymers of tetrafluoroethylene and Call hexafluoropropylene. Other examples of polymers which can be shaped into fibers are the polymers of the polyamide-imide type, such as 4-, the polytrimellitic amide-imides or the polyamides derived from wholly aromatic reagents.

The above-mentioned fiber-forming polyamide-imides may be of the same type as those as Binders used in the invention. It can therefore be polymers that are im essentially have a number of groupings of the formula I.

It can also be polymers which, in addition to the groupings of the formula I, groupings of the γ-, formula

- NH-Q — NH-CO-Z — CO— (IV)
and / or groupings of the formula e, o

—NH-Q — NH-CO - / \ - CO— (V)

I I b5

SO ₃ - - M " ⁺
in which Q has the meaning given above, Z is a divalent aliphatic, cycloaliphatic or aromatic radical, M is an alkali or alkaline earth metal ion and η is 1 or 2

Examples of radicals represented by Z can be arylene radicals such as, for example represented by Q, alkylene radicals having 2 to 12 carbon atoms, such as ethylene, trimethylene, Tetramethylene, hexamethylene and octamethylene residues, and cycloalkylene radicals with 5 or 6 carbon atoms in the ring, such as cyclopentylene and cyclohexylene radicals.

The fully aromatic polyamides can be defined as products made up of repetitive Units of the formula

R ₂ R ₂ OO

- N — Q — N — C — Q — C—

(Vl)

exist, in which the various symbols Q, which can be the same or different from one another, have the meaning given above and the symbols R ₂ , which can be the same or different from one another, each denote a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms.

It should be noted that a single type of Fibers or, on the other hand, a mixture of fibers can be used. These fibers generally have a length between 0.2 and 50 mm and a titer, expressed in decitex, between 0.5 and 20.

The invention also relates to a method of making the nonwoven fabrics described above Nonwovens.

The procedure essentially consists of:

a) to form a dry fiber fleece,

b) the fleece obtained with a polyamide-imide solution to bring in contact and

c) drying the product thus obtained.

The fiber fleece can be obtained in a dry way or in a wet way, also called a paper route will.

In the following, the term "fleece" is used to denote the textile part of the invention Fiber fleece, considered in the final stage of its manufacture, reserved, this fleece itself made up of several Fiber layers called "pile" can be obtained.

In particular, according to the dry technique, the fleece can be made of parallel, crossed or arbitrary arranged fibers exist. In general, the nonwovens with parallel fibers are made by carding obtain. Considering the great lightness of the pile obtained by this technique, several can be made Align piles on top of each other prior to using the binder to obtain the desired thickness. the Nonwovens with crossed fibers are generally made by laying piles with parallel Fibers obtained, these fibers being oriented in different directions according to the piles. in the in general, the angle of intersection of the nonwovens will function as a function of the ultimate use of the nonwoven Product chosen. The nonwoven fabric thus obtained can be used as such. However, it is in the it is generally desirable to press this fleece in order to solidify it.

The non-woven fabric can also be made of arbitrarily arranged

th fibers. In general, there is the usual one Technique in it, the fibers previously opened with mechanical devices under the action of a To spray a jet of air onto a screen compressor.

Other techniques can be used to keep nonwovens dry. So you can, if The fiber-forming material is suitable, nonwovens Produce directly at the outlet of the spinneret. The interweaving of the fibers can be different Techniques currently known and commonly referred to as "spun-bonded" are designated.

It should be noted that the methods briefly outlined above do not limit the invention to the are intended to represent the nonwovens obtained according to this information. In particular, the mechanical treatments which are generally made in the manufacture of nonwovens, such as needling with its various variants, within the scope of the invention.

Furthermore, the production of nonwovens by paper should extend to every nonwoven that is passed through Removal of water from a fiber dispersion is obtained through a porous support. The working techniques such as agitation and fiber dispersion conditions, manufacturing speed of the fiber fleece or the operating material used in this operation! are known.

The cohesion of the fiber fleece obtained as described above is based in principle only on the interlacing of the fibers, and the application of the binder should only take place in the following stage of the process. It however, it should be noted that it is possible or sometimes desirable, particularly in the case of fibers which Difficult to anchor among each other, to bind the fibers somewhat in the stage of manufacture of the fleece. the The use of such a supplementary binder is particularly important in the case of production by the wet route facilitated because this supplementary binder can be incorporated into the fiber dispersion. Since this Binder is only used to enable handling of the fleece, the quantitative proportion can this binder be low (for example 5 to 30%, based on the weight of the fibers), and that Main feature of this product is in the solvents of the polyamide-imide to be insoluble. An example of a particularly recommended binder is Polyvinyl alcohol.

Regardless of how the fiber fleece is manufactured, it should be dry at the time it is brought into contact with the binder. If the fleece was produced by a wet method, it is therefore necessary to remove the water. In general, the fleece is heated for 5 minutes to 1 hour at a temperature between 50 and 100 ^° C., optionally under partial vacuum.

The polyamide-imide is used in the form of a solution. The solvent used is im general polar organic solvents, such as, for example, N-methylpyrrolidone- (2), dimethylformabo mid, dimethylacetamide, dimethylsulfoxide, N-methylcaprolactam, a cresol, xylene or a mixture of these solvents.

The concentration of the polyamic acid solutions is generally between 0.1 and 30% and preferably between 0.5 and 10%.

The treatment of the fiber fleece with the binder solution can be carried out in various ways. So can you immerse the fleece in the binder solution. You can also use the fleece on one or both sides overlay and repeat this operation one or more times. You can also do that Spray the binder solution onto the fleece, for example using a spray gun with. Compressed air It should be noted that the techniques are customary and that equivalent techniques are used within the framework of the Invention lies.

The amount of polyamide-imide applied to the fiber fleece (expressed as the weight of the dry polymer per m ^{2 of} surface area of the fleece) is generally between 1 and 50 g. An amount between 1.5 and 20 g / m ² makes it possible to obtain products with excellent properties.

After the nonwoven has been treated with the binder, the solvent is removed. It is advantageous in a first step to press the fleece. The solvent can then be evaporated permit. However, it is desirable, especially if the solvent of the binder is the nonwoven fabric forming fibers can loosen or swell, which can be the case when the fibers are made of the same Polymers such as the binder come from to speed up the removal of the solvent, for example by applying a vacuum and / or heating to a temperature between 100 and 250 ° C during a period of time which, depending on the temperature, can be 5 minutes to 4 hours.

The nonwoven products according to the invention are distinguished by high mechanical properties both at room temperature and at high temperature, for example 200 ° C.

They can be used in various industrial applications be used, such as in particular for the production of filters for smoke dedusting or for the continuous regeneration of motor oils, as materials for electrical insulation Applications and as a catalyst carrier.

The following examples serve to further illustrate the invention.

Examples 1 to 3

a) With manual stirring in 500 cm ^{3 of} water containing 2.5 g of a surface-active agent (sodium salt of a secondary alkyl sulfate), 1.8 g of aromatic polyamide fibers derived from a polymer containing a number of groupings of the formula

-νη-λΑ-νη-c

having. The average length of the fibers is 6 mm and their titer is 2.2 dtex.

This dispersion is in a paper machine (Formette Frank, equipped with a sieve with rectangular mesh of 120 χ 240 μ, that with a Cotton lining is covered) introduced, whereby the mixture kept in motion to about 61 by Addition of water is brought. You remove that

Water by applying a vacuum (reduced pressure to 100 mm Hg). The pile obtained is placed while still wet between two sheets of polyfluoroethylene propylene (FEP), one of which is perforated to a degree of approximately one perforation with a diameter of 0.9 mm / cm ² surface. The whole is then dried for 9 minutes at 93 ^° C. under partial vacuum (10 mm Hg). After drying, remove the non-perforated FEP film from the whole.

b) Impregnation of the unbonded pile thus produced (weight: about 50 g / m ² ) is carried out as follows:

Inside a suction filter with an inner diameter of 240 mm, which is placed on a vacuum flask, a filter paper sheet and then the unbonded pile supported by the perforated FEP film are successively attached in such a way that the perforated FEP film comes into contact with the filter paper is located. It is then impregnated with about 30 cm ^{3 of} a solution of the polyamide-imide resin defined below and the excess of the solution is reduced

by applying a vacuum (pressure reduced to 100 mm Hg) for 5 minutes.

The fleece obtained, still supported by the FEP film, is placed in a ventilated oven at 200 ° C. during Dried for 4 minutes. The FEP film is removed and the fleece is heated again for 15 minutes at 250 ° C.

The polyamide-imide resin is produced by condensation of trimellitic anhydride with 4,4'-diisocyanatodiphenyl ether made with a molar excess of diisocyanate of 3%. The resin has a reduced Viscosity of 48 cmVg, measured in a 0.5% solution in N-methylpyrrolidone. It comes in the form of a Solution used in the same solvent with the concentrations given below.

The table below shows the concentrations of the impregnation solution and the properties of the products obtained. The tensile strength (hereinafter referred to as tensile strength) and the elongation at break are according to the AFNOR Q 03 004 standard certainly. The tensile strength is expressed in kg for a width of 5 cm.

Tabel 1 weight Up tensile strenght at 200 C Tear length at 200 ¹ C Elongation at break at 200 C at Dry brought it game extract Ender Bandage at 20 C at 20 C at 20 C of things middle Bads *) nis g / m ² kg m % 8.3 11.80 4060 6.8 g / m ² 6.1 kg 10.07 m 3600 % 7th 58.1 2.8 18.42 4.55 6340 1707 6.7 3.9 1 3.5 55.9 18.73 6700 6.4 2 3.5 53.3 7.40 2775 2.8 3 1.5

*) In g resin for 100 g solution.

Examples 4 to 8

a) 0.180 g of a completely saponified polyvinyl alcohol with an average particle size of about 120 microns is dispersed in 50 cm ^{3 of water with manual stirring.}

In addition, 1.8 g of the aromatic polyamide fibers used in Examples 1 to 3 are dispersed in 500 cm ^{3 of} water containing 2.5 g of a surface-active agent (sodium salt of a secondary alkyl sulfate) with manual stirring.

The two dispersions are then mixed and then introduced into a paper machine (Formette FRANCK, equipped with a sieve with rectangular meshes of 120 × 240 microns), the mixture kept in motion being brought to about 6 l by adding water. The water is removed by applying a vacuum (reduced pressure to 100 mm Hg). The pile obtained is ^{dried at 93 °} C. for 9 minutes under partial vacuum (10 mm Hg).

b) The pile produced as indicated above is then in a full bath in the solution of the in Examples 1 to 3 used polyamide-imide resin impregnated and then by guiding between the rollers one Hand wringer pressed

This wringer consists of two rubber rollers that are mounted on parallel axes and with are coated with a polyethylene glycol terephthalate film. Each roller has a length of 30 cm and one

_w diameter of 45 mm. The distance is adjusted so that a passage of about 10/100 mm remains between the rollers.

c) The fleece obtained is dried ^{at 250 ° C. in a ventilated oven.} To avoid clogging

_b0 bens with the carrier, a film made of polyfluoroethylene propylene (FEP) is arranged between this and the fleece.

After 4 minutes at 250 ^° C., the fleece is detached from the FEP film and drying is then continued for 15 minutes.

_h r, You determine the properties of the non-woven product.

These results are given in Table II below shown.

ίο

Table II

example

Dry extract
of
Bads

weight

binder-

things-

nis

g / m ²

Upset
binder

g / m ²

Tensile strength, tear length, elongation at break

at 20 C "at 200 C at 20 C at 200 C at 20 C at 200 C

kg

kg

5
5
3.5

1.5
1.5

68.5
63.3
63.5
60.8
59.4

Il
9.7
7th

3.3
2.9

28.8 26.3

22.5 17.2 15.4 19.2

15.4

13th
8.4
7.65

8395
8305
7075
5640
5190

5590
4880
4085
2765
2580

6.4 6.4 5.8 6.1

8.6 6.1 5.1

4.7

Examples 9-13

The experiments of Examples 4 to 8 are repeated, using a solution as the impregnation bath by condensation of trimellitic anhydride with 4,4'-diisocyanatodiphenylmethane with 3% molar Polyamide-imide resin obtained in excess of diisocyanate in a mixture of N-methylpyrrolidone and Xylene used in a weight ratio of 80:20.

The resin used has a reduced viscosity of 47 cmVg (measured as before).

The properties of the products obtained are summarized in the table below.

Tabel III weight Up tensile strenght at 200 C Tear length at 200 C Elongation at break at 200 C at Dry- brought it game extracl Ender Bandage at 20 C at 20 C at 20 C of things middle Bads nis g / m ² kg m % 9.4 15.9 4900 7.3 g / m ² 10.4 kg 18.6 ni 5575 % 10.8 64.8 7.8 22.7 16.6 7010 5000 6th 10.6 9 5 66.6 2.9 21.8 11.1 6570 3725 5.8 6.2 10 5 66.5 3.5 20.6 13.2 6185 3975 5.7 6th Il 3.5 59.4 16.4 5515 5 12th 1.5 59.4 17.2 5805 4.5 13th 1.5

Examples 14 to 16

The experiments of some of Examples 4 to 8 are repeated, the fibers being carbon fibers with an average length of 6 mm and an average diameter of 9 microns.

The properties of the obtained nonwoven products are shown in Table IV below specified.

Tubelle IV weight
Child
ZCUg-
nis Up
brought it
Bandage
middle tensile strenght
at 20 C at 200 C Tear length
at 20 C at 200 C Elongation at break
at 20 C at 200 ( % at
game Dry
extract
of
Bads g / m ² g / m ² kg kg m m % 0.8 73.4 17.7 4.15 2.7 1135 735 0 0.8 14th 5 63.5 10.3 2.85 1.85 900 585 0 0.8 15th 3.5 62 7th 1.05 0.95 335 305 0 16 1.5

Examples 17-19

The procedure described in Examples 4 to 8 is followed and a pile is produced in this way Glass fibers (average length: 3 mm, through ■> average diameter: 10 μ), bound with a polyvinyl alcohol. 25% polyvinyl alcohol is used, based on the glass fibers, d. H. 0.450 g polyvinyl alcohol for 1.800 g glass fibers.

The pile produced in this way becomes after 9 minutes

Drying at 93 ° C. under partial vacuum (10 mm Hg) in a full bath in the manner described in Examples 4 to 8 used polyamide-imide-resin solution and then also under the same conditions treated.

Depending on the concentration of the heat-resistant resin impregnation bath, products are obtained the properties of which are given in the table below.

Tabel V weight
Ender
things
nis Up
brought it
Bandage
middle tensile strenght
at 20 C at 200 C Tear length
at 20 C at 200 C Elongation at break
at 20 C at 200 (. " I. at
game Dry
extract
of
Bads g / m ² g / m ² kg kg m ni %% j 65.2 7.8 11.30 5.40 3470 1660 0 1.1 17th 5 67.9 5.5 8.85 5.15 2610 1525 0 1.2 I. 18th 3.5 58.8 1.8 5.75 4.05 1950 1375 0 1.2 19th 1.5

Examples 20-23

As in Examples 4 to 8, nonwoven piles made of aromatic polyamide fibers are provided with something Polyvinyl alcohol bound here, with the previously described (Examples 4 to 8, paragraph a) specified amounts and works under the conditions described there.

These piles are then tied with the aid of a solution of one used in Examples 9 to 13 Polytrimellitamide imides, such with a mixture of N-methylpyrrolidone and xylene (8:20) diluted that the Concentration of dry product is 10%. This solution is applied to the pile by means of a pressurized air applied by a spray gun fed by 1 bar. The amount of binder applied is set by variation the duration of the injection.

The fleece obtained is subjected to the heat treatment described in Examples 4 to 8 (paragraph c).

The properties of the obtained nonwoven products are shown in the following table.

Tabel Vl weight
Child
ZCUg-
nis Up
brought it
Bandage
middle tensile strenght
at 20 C at 200 C Reililängj
at 20 C ■ at 200 C Elongation at break
at 20 C at 200 ( % lOOMoU ^ '- Diisocyanato-diphenylmethane at
game Spray
üaucr g / m ² g / no kg kg m m % 4.8 lake 59.7 3 13.15 7.9 4410 2660 4.9 5.6 20th 5 60.4 4th 17.05 10.8 5660 3585 5.4 8.5 21 5 66.4 12th 24.45 15.2 7380 4580 6.9 - 22nd 15th 67.5 Il 27.75 17.7 8240 5240 8.1 23 15th example 24

The procedure is as in Examples 20 to 23, but the fibers used are polytrimellithamide-imide fibers with an average length of 6 mm and a titer of 2.2 dtex, obtained by dry spinning of a polymer with an inherent viscosity of 1.01 (solution of 5 g / l in N-methylpyrrolidone). This polymer is the reaction product of

y
20 moles of terephthalic acid.

The properties of the obtained nonwoven products are as follows, for a spray time of 5 seconds:

weight 62.2 g / m ² Weight of applied binder 4.6 g / m ²

Tensile strength at 20 ° C
(for a width of 5 cm)
Tensile strength at 200 ° C
(for a width of 5 cm)
Tenacity at 2O ⁰ C.
Tear length at 200 ° C
Elongation at break at 20 ° C
Elongation at break at 200 ° C

7.25 kg

4.85 kg 2330 m 1560 m 6.1% 7%

Example 25

A non-woven product made of asbestos fibers without a binder (asbestos paper) is impregnated with the in Examples 4 to 8 used polyamide-imide resin solution.

The properties of the paper used are: thickness: 220 μ; Weight: 200 g / m ² ; the fibers have an average diameter of 10 μ and an average length between 10 and 100 μ; the

The tensile strength of this paper at 20 ° C is 1.635 kg (for a width of 5 cm).

The characteristics of the products obtained are as follows:

Dry extract of 5% Impregnation solution Weight of the applied 7 g / m * Binder 6.70 kg Tensile strength at 20 ° C (Width 5 cm) 6.22 kg at 200 ° C (Width 5 cm) 1.2% Elongation at break at 20 ° C (Width 5 cm) 2.2% at 200 ° C (Width 5 cm) 680 m Tear length at 20 ° C 633 m at 200 ° C

Claims (3)

Patent claims: 1. Non-woven fiber fleece, the fibers of which are interconnected by a synthetic polymer are bound, characterized in that a) the material forming the fibers is infusible or has a melting point above 180 ^° C. and b) the binder is a polyamide-imide, the proportion by weight of which is 5 to 150% by weight of the dry fibers used. 2. Nonwoven fiber fleece according to claim 1, characterized in that the fibers are inorganic and / or are organic fibers. 3. Nonwoven fiber fleece according to claim 1 or 2, characterized in that the binder is a Polymer is that a number of groupings of the formula