FR2634479A1 - THERMALLY INSULATING FIBER FIBER BODIES AND PROCESS FOR PRODUCING THESE BODIES - Google Patents

Abstract

Thermally insulating shaped bodies made of incombustible or refractory ceramic fibers, of vermiculite, with a ceramic fiber / vermiculite ratio of 80/20 to 30/70, and of 5 to 40% by weight, based on the total composition, of fibrils organic polymers, as well as temporary and / or permanent binders, characterized in that they contain unexpanded vermiculite with a maximum grain size of 1.0 mm. The invention also relates to a method of manufacturing such thermally insulating shaped bodies. These thermally insulating shaped bodies have the advantage of having good values of expansion pressure and resistance to erosion by the action of gases, in particular air.

Description

Thermally insulating shaped fiber bodies and method of manufacture

of these bodies

  The invention relates to thermally shaped bodies

  insulators made of non-combustible or refractory ceramic fiber, in vermiculite, with a ratio of ceramic fibers /

  vermiculite from 80/20 to 30/70, and with 5 to 40% by weight,

  brought to the total composition, of polymer fibrils

  organic, as well as temporary and permanent binders.

  In the German patent application P 37 01 511.7 are described thermally insulating shaped bodies of the type

  indicated above. The body manufacturing process

  born using vermiculite described in this application uses grain-size vermiculite up to

2 mm.

  It has now been discovered that shaped bodies

  thermally insulating materials with more interesting properties.

  in particular better extension properties,

  when they are implemented, that is, when they are used

  at temperatures above 500 C, may be

  obtained when using unexpanded vermiculite with

  with a maximum grain size of 1.0 mm. In this way, it is possible to improve what is called the expansion pressure of the shaped bodies obtained, as well as

their resistance to erosion.

  Thermally insulating shaped bodies of the species described above are characterized according to the invention by the fact that they contain unexpanded vermiculite

  with a maximum grain size of 1.0 mm.

  According to a preferred embodiment, the thermally insulating shaped bodies according to the invention contain unexpanded vermiculite with the maximum grain size indicated above of 1.0 mm, at least 80% of the vermiculite contained in said bodies. having a

  grain size up to 0.5 mm. This form of realization

  advantage that erosion resistance can

to be further improved.

  According to another preferred embodiment, the thermally insulating shaped bodies according to the invention contain unexpanded ground vermiculite with the maximum grain size indicated above of 1.0 mm.

  minus 95% of vermiculite with a maximum grain size of

  male of 0.5 mm. This embodiment presents this

  advantage that the texture of the shaped bodies is considerable-

  improved and that erosion resistance in a cou-

gaseous content is further increased.

  According to another preferred embodiment, the shaped bodies according to the invention contain a mixture of unexpanded crushed vermiculite and non-expanded vermiculite.

  expanded by sieving, of a maximum grain size

  1.0 mm, in a proportion of 30/70 to 70/30, of

  from 40/60 to 60/40. This embodiment has the advantage that a very even distribution of the grains is obtained in such a way that particularly advantageous properties are obtained from the point of view of the pressure.

  expansion and resistance to erosion.

  The invention further relates to a method of

  of the thermally insulating shaped bodies described above, in which a shaped body made of fiber mats is conventionally produced from an aqueous suspension of the starting materials, a fiber mat is formed from this material. dried, optionally heat-treated to

  a temperature sufficient for the fusion of organic fibrils

  and, where appropriate, thermoformed, process in which vermiculite is used in a proportion of 80/20 to 30/70 ceramic / vermiculite fibers, which is characterized in that in the starting dispersion it is used unexpanded vermiculite with a maximum grain size of 1.0 mm, preferably unexpanded vermiculite up to 1.0 mm in grain size, of which at least 80% has a grain size <0 , 5mm or ground vermiculite no

  at least 95% of which has a grain size <0.5 mm.

  According to another preferred embodiment of the

  According to the invention, a mixture of unexpanded crushed vermiculite and unexpanded vermiculite obtained by sieving with a grain size of up to 1.0 mm is used in the starting dispersion, where the vermiculite obtained by grinding and the vermiculite obtained by sieving are in a

proportion of 30/70 to 70/30.

  For the realization of the invention, use is made of

  conventional ceramic fibers, incombustible or refractory.

  These may have a thickness of 1 to 10 μm and a length of 1 to 10 mm; classically, such ceramic fibers are defined by their classification temperature which

  can for example rise to 1260 or 1600 C.

  The vermiculite used according to the invention

  is a common commercial product. To get a vermicula

  lite unexpanded with a maximum grain size of 1.0 mm, one can either sift natural vermiculite to this size

  1.0 mm, or grind natural vermiculite. In observing

  before a sufficient milling time, a product with a maximum grain size of 1.0 mm can be obtained, or the ground vermiculite can, for safety reasons and to exclude particles of a size greater than 1.0. mm, to be

again sifted.

  The organic polymer fibrils used according to the invention are common commercial products, which can be made from different

  polymers. Preferably, poly-fibrils are used.

  olefins, for example polyethylene fibrils with a softening point of 125 to 135 C or polypropylene

  with a softening point of 155 to 165 C.

  Temporary or permanent binders used in

  according to the invention correspond to the binders mentioned in

DE-OS 34 44 397.

  The manufacturing method of the shaped bodies according to the invention is carried out in a conventional manner, that is to say that the starting materials are dispersed in a sufficient quantity of water, with the aid of a stirrer or in a mixer adapted to form a dispersion. Then the shaping of

  shaped bodies made of fiber mats is carried out in a conventional manner.

  for example on screen molds or by settling of

the aqueous suspension.

  By these forming techniques, mat-shaped shaped bodies of different thicknesses are conventionally obtained, the thickness depending on the amount of dispersion filtered and accumulated on a sieve and which can be

set with this one.

  These raw shaped products in the form of mats

  The final shaped bodies can then be formed either directly or during further processing, in which process these mats are heated to temperatures of up to 120 ° C. temperatures such that the fibril polymer is malleable, for example, in the case of the use of polyethylene fibrils with a melting point of about 135 C, at temperatures of 160 to 180 C, a pressure of 5 to 200 bar, preferably from 10 to 50 bar, being,

  appropriately, applied. Heating at room temperature

  high rature of between 160 and 180 ° C. in general only lasts a few minutes, for example 3 to 20 minutes, depending on the thickness of the raw products to be shaped, for example

example of mats.

  As a result of the fibril content of the body

  In addition, it is also possible to manufacture shaped bodies from two fractions of the raw shaped product by fusing together these fractions of the raw shaped product at their compression contact surfaces at high levels.

  temperatures, for example at 180 ° C., for 3 minutes at 80 bar.

  For this embodiment, the fibril content is preferably set at 20 to 40% by weight, based on the dried shaped body. In the case of complicated shaped bodies, the cooling must be carried out by keeping the mold adjusted to the shaped body, so that no deformation of the body

  definitive fashioned does happen.

  The invention is explained in more detail

using the following examples.

Example 1

  3 kg of unexpanded vermiculite, obtained by

  With a grain size of up to 1.0 mm, 4 kg of ceramic fibers 1 to 3 Nm thick, 1 to 1 mm long and a classification temperature of 1260 C are regularly dispersed by means of an agitator in 600 l of water contained in a container. After addition of 4.1 kg of a 3% dispersion of polyethylene fibrils

  with a melting point of about 135 C and 300 g of a

  aqueous polyacrylate persion causes flocculation

  dispersion by adding a polyacrylate solution

  mide, by filtration of the water at the trunk, then drying, a

  shaped body made of fiber mats is formed on a sieve.

  This shaped body with a bulk density of approximately 900 kg / m3 is used as a seat or insulating jacket in machines or thermal conduits. The shaped body possesses, after heat treatment, excellent shape stability with simultaneous strength and elasticity and is suitable for mounting and fixing catalysts

  and / or ceramic filters integrated in pipes.

  The shaped body has an expansion pressure of 0.6 N / mm 2, determined by the following measuring method: the square sample is in the form of a plate of regular thickness, the load surface, provided with a hole in the middle, is measured accurately in mm2 for the determination of the specific expansion pressure and placed

  under a pressure measuring box. Before the first heat

  gauge, a force of 10 N is applied on the total surface.

  The speed of heating and cooling

  reaches about 10 C / min. As a control, 7 cy-

  keys from 75 to 750 C, then back to 75 C; the values given in the table refer to the second cycle, because cycle 1 presents

  often an abnormal value due to degassing of vermiculite.

  The erosion values given in the table for Examples 2 to 4 are determined by the following measurement method: the 60x15x5 mm sample is set in such a way that the outer surface subjected to the blast is approximately mm 2. Before the test, the fixed sample is expanded by annealing at a temperature of 750 ° C (without interruption). Then the sample is subjected on its outside face to the breath of the compressed air coming out of a nozzle of 15 mm diameter placed at a distance of 25 mm. The pressure of the compressed air is measured on the pressure side at a distance of 1 m before the nozzle and maintained at a constant level of 1.25 bar. The sample and its fixture are weighed at different time intervals and the weight loss is determined. The values given in the table refer to blowing times

60 minutes.

Examples 2 to 4:

  This procedure of Example 1 is repeated in use.

  reading the starting materials indicated in the table below.

  efore. We thus obtain shaped bodies presenting the pro-

  properties shown in the following table.

BOARD

  Examples 2 3 4 Ceramic fibers, TC = 12600C (kg) 4 4 4 Polyethylene fibrils (kg) 4.1 2.5 2.5 Polyacrylate dispersion (g) 300 300 300 Vermiculite unexpanded, sieved to 1 mm max .; 80% <0.5 mm (kg) 1.5 6 2 Non-expanded vermiculite, ground to 1 mm max .: 95% <0.5 mm (kg) - - 2 Gross density of the shaped body (kg / m3).

800 1000 900 Expansion pressure (N / mm2). 0.2 0.8 0.6 Erosion (after 60 min) (mg) 0.2 0.5 0.1

Claims (8)

  1. Thermally insulating shaped bodies made of non-combustible or refractory ceramic fibers, of vermiculite, with a ceramic fiber / vermiculite ratio of 80/20 to 30/70, and with 5 to 40% by weight, based on the total composition, of fibrils of organic polymers, as well as binders   temporary and permanent, characterized in that they contain   unexpanded vermiculite of a grain size maximum of 1.0 mm.   2. Thermally insulated molded bodies according to   claim 1, characterized in that they contain   unexpanded miculite with a maximum grain size of   1.0 mm, of which at least 80% is made up of less than 0.5 mm.   Thermally insulating shaped bodies according to claim 1 or 2, characterized in that they contain   vermiculite, milled unexpanded, of which at least 95% is   with grains <0.5 mm in size.   4. thermally insulating shaped bodies according to claim 1 or 2, characterized in that they contain a mixture of unexpanded crushed vermiculite and unexpanded vermiculite, obtained by sieving, with a grain size <1 .mu.m,   in a proportion of 30/70 to 70/30.   5. Method of manufacturing the thermally shaped bodies   mically insulating materials according to any of the claims   in which a shaped body made of fiber mats is conventionally produced from an aqueous suspension of the starting materials, from which is formed a fiber mat which is dried, optionally heat-treated with   a temperature sufficient for the fusion of organic fibrils   and, where appropriate, thermoformed, a process in which   uses vermiculite in a proportion of ceramics fibers   from 80/20 to 30/70, characterized in that the vermiculite used is unexpanded vermiculite of a   grain size up to 1.0 mm.   6. Process according to claim 5 characterized in   the vermiculite used is vermiculite not ex-   of which at least 80% is made from 0.5 mm.   7. Process according to Claim 5 or 6, characterized in that the vermiculite used is unexpanded crushed vermiculite, of which at least 95% consists of grains of size 0.5 mm.   8. Method according to claim 5 or 6, characterized in that the vermiculite used is a mixture of unexpanded crushed vermiculite and unexpanded vermiculite obtained   by sieving with a grain size of $ 1.0 mm, in a portion of 30/70 to 70/30.