WO2010057321A1

WO2010057321A1 - Corrosion-resistant lining laminate

Info

Publication number: WO2010057321A1
Application number: PCT/CH2009/000340
Authority: WO
Inventors: Beat Werthmüller; Urs Wehrli
Original assignee: Quadrant Epp Ag
Priority date: 2008-11-18
Filing date: 2009-10-23
Publication date: 2010-05-27
Also published as: CH699926A1; CH699926B1; DE212009000234U1

Abstract

A lining laminate for corrosive media, particularly for hydrofluoric acid, comprises a sealing layer (2) made of a fluoropolymer and a lamination (4) that is applied onto one side of the sealing layer, said lamination comprising a knitted fabric which is partially embedded into the sealing layer and which partially protrudes. The knitted fabric is made from fully fluorinated polymer, in particular PTFE. In a method for producing the lining laminate, appropriate webs of the fluoropolymer and of the knitted fabric are continuously pressed together at temperatures above the softening range of the fluoropolymer.

Description

Corrosion resistant lining laminate

Technical area

The invention relates to a corrosion-resistant lining laminate according to the preamble of claim 1, a method for its production and a use thereof.

State of the art

For the storage and transport of corrosive or aggressive media, it is known to line containers and pipes with an inner layer of a chemical-resistant plastic, in particular of a fluoroplastic. For example, in DE-OS 1 936 118 such a container is described, which is formed by a mechanically or chemically roughened fluoroplastic body with a shell arranged around it made of glass fiber reinforced epoxy or polyester resin. However, it has been found that the bond strength of such roughened surface arrangements is partially inadequate.

Furthermore, for use in corrosive environments, chemical resistant liner laminates are known which comprise a layer of a fluoroplastic with a single-sided adhesion promoter in the form of a knitted or woven fabric. The adhesion promoter is intended to attach the laminate with the aid of an adhesive system to a structure to be lined, such as a steel container or another part of the plant. Examples of play are web-like commercially liner laminates of tetrafluoro ethylene perfluoroalkyl vinyl ether copolymer (also referred to as "perfluoroalkoxy" or PFA) are known which are equipped as standard with a lamination in the form of a glass fiber fabric (for example the product "Symalit ^® PFA" from Quadrant EPP AG in Lenzburg, Switzerland). But also other lining laminates such as Symalit® FEP and Symalit® MFA with fiberglass knit Lamination as well as Symalit® ECTFE and Symalit® PVDF with synthetic knitted lamination are commercially available.

Applications of such liner laminates include, but are not limited to, chlorine electrolysis and sodium chlorate production, as well as other applications where severe corrosion protection is required.

However, it has been found that the above-mentioned linings, especially in the presence of hydrofluoric acid in the process under certain conditions (depending on the concentration, temperature, pressure) only have a limited life, i. E. After a certain life of, for example, 2 to 3 years, the lining can partially detach from the container wall, since the glass-knitted lamination loses its inherent strength by the permeable hydrofluoric acid.

Presentation of the invention

The object of the invention is to provide an improved lining laminate, which is particularly useful in contact with hydrofluoric acid and granted a longer service life when properly processed. Further objects of the invention are to specify a method for producing the lining laminate according to the invention and a use thereof.

These objects are achieved according to the invention by the characterizing features of claim 1, by the manufacturing method according to claim 4 and by the use according to claim.

The lining laminate according to the invention comprises a sealing layer made of a fluoropolymer and a lamination applied on one side of the sealing layer, wherein the lamination comprises a fabric which is partially embedded in the sealing layer and partially projecting from a fully fluorinated fabric. is polymerized. The sealing layer has a thickness of at least 0.8 mm and is basically not limited to the top.

The measures according to the invention initially have the consequence that the lamination is resistant to aggressive media and in particular hydrofluoric acid and accordingly the lining laminates can be used with far improved service life for hydrofluoric acid. While other fibers which would be chemically resistant to hydrofluoric acid (e.g., carbon fibers or ECR glass fibers) are not knitable and thus obtainable only as sheet, non-drape fabrics, the present invention provides lamination with three-dimensional formability or stretchability. Thus, the inventive liner laminate can also be used for deep-drawn parts. It will be appreciated that, depending on the configuration of the container or component to be lined, the lining is made, if necessary, from a plurality of blanks of the lining laminate, which are welded together.

It is known that all liquid and gaseous media diffuse into some plastic in some amount and permeate through it over time. The time until incipient permeation and the permeation rate are influenced by many factors. The most important are: medium (molecular size, polarity, concentration), temperature gradient, pressure gradient, thickness of the plastic layer. It is also known that hydrofluoric acid, after penetrating the fluoroplastic layer, chemically attacks the usually used laminates made of polyester or glass fiber knit. The concomitant disintegration of the liner results in a highly undesirable decrease in composite adhesion between the liner laminate and backing material, which may later result in delamination of the liner from the vessel wall. In contrast, the knitted fabric formed from a fully fluorinated polymer is not attacked, resulting in a comparatively longer service life of the container. The lining laminate according to the invention can be used both as an inner liner in a steel lining and as an inner liner in a GFRP dual laminate construction.

According to a second aspect of the invention, there is provided a method of making a liner laminate by continuously compressing respective webs of the fluoropolymer and the fabric at temperatures above the softening range of the fluoropolymer.

According to a further aspect of the invention, lining laminate according to the invention is used for the inner lining of containers for aggressive media.

Preferred embodiments of the invention are defined in the dependent claims.

Basically come as a material for the sealing layer, various thermoplastic fluoroplastics in question. Advantageously, the fluoroplastic is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter also: PFA). The knitted fabric used for the lamination of a fully fluorinated polymer is preferably made of polytetrafluoroethylene (hereinafter also: PTFE), in particular made of a PTFE yarn, since PTFE has a very good chemical resistance to almost all chemicals, especially against hydrofluoric acid.

Brief description of the drawings

Exemplary embodiments of the invention will be described in greater detail below with reference to the drawings, in which:

Fig. 1 shows a portion of a lining laminate, in perspective

Presentation; FIG. 2 shows a section of the lining laminate of FIG. 1, in a vertical sectional view; FIG.

3 shows a section of a container equipped with the lining laminate of FIG. 1, in a vertical sectional view; FIG. and

Fig. 4 shows a detail of a Duallaminat construction with a

Lining laminate of Fig. 1 and a support structure made of glass fiber reinforced plastic, in a vertical sectional view.

Ways to carry out the invention

The lining laminate shown in FIGS. 1 and 2 comprises a sealing layer 2 made of a fluoropolymer and a lamination 4 applied on one side thereof. The fluoropolymer for the sealing layer used is in particular a tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA). The lamination is formed by a partially embedded in the sealing layer and partially protruding knit of a fully fluorinated polymer such as PTFE.

The liner serves as an adhesive layer to attach the liner laminate to a container or to reinforce it with a fiber reinforced vinyl ester resin to a dual laminate construction. This is explained in more detail in FIGS. 3 and 4.

As can be seen from FIG. 3, for attaching the lining laminate to the inner wall Wi of a container wall W, first the lining 4 is covered with a suitable adhesive, for example with an epoxy adhesive E. In this case, the fabric 4 is impregnated with the adhesive E. Thereafter, the liner 4 is pressed against the inner wall Wi and held until the adhesive has cured. It is understood that the inner wall according to the used adhesive system is pretreated, so for example roughened and degreased.

4 shows a dual laminate in which the lining 4 of the lining laminate according to the invention is bonded to a layer G of a glass-fiber-reinforced polyester or vinyl ester resin.

Such a plant part (container, pipeline, reactor, etc.) can be filled with a corrosive medium M such as hydrofluoric acid. Even if small amounts of hydrofluoric acid penetrate through the sealing layer 2 over time, the lining 4 remains undamaged and can further serve as an adhesive layer in which the epoxy adhesive or reinforcing resin is anchored.

The production of the lining laminate is preferably carried out by continuous pressing. In this process, a melt layer of the fluoropolymer provided as the sealing layer and an equally wide web of the fully fluorinated polymer knit are combined in a calender and rolled between the heated calender rolls to form a lining laminate.

Examples

The lining laminates were produced in lengths of 10 m length and 1.25 m width with a thickness of either 0.8, 1.5 or 2.8 mm. The lamination used was a knit fabric of fibrillated PTFE yarn with a titre of 880 dtex.

In the production of the liner laminate by the extrusion process, the PFA plastic melt (processing temperature to 380 ⁰ C) of the lining laminate, which is provided by the extruder, was fed via a slot die to the nip of a calender with rolling temperatures of up to 280 ⁰ C. The fabric also came from the roll to the nip and was embedded in the plastic melt resp. compressed (splitting forces up to 2000 N / cm).

Alternatively, the production by the pressing process would be considered. In this case, an already produced film is heated on one side until it can either be pressed between rolls or on a double belt press with the Kashiergut.

Claims

claims

A corrosion-resistant liner laminate comprising a fluoropolymer sealant layer (2) and a liner (4) applied to one side of the sealant layer, the sealant layer having a thickness of at least 0.8 mm and wherein the liner has a partially embedded in the sealant layer partially protruding knitted fabric, characterized in that the knitted fabric is formed from a fully fluorinated polymer.

2. The lining laminate according to claim 1, wherein the sealing layer is formed of perfluoroalkyl vinyl ether copolymer (PFA).

3. Lining laminate according to claim 1 or 2, wherein the knitted fabric of polytetrafluoroethylene, in particular in the form of yarn, is formed.

A method of producing a lining laminate according to any one of claims 1 to 3, wherein respective webs of the fluoropolymer and the knit are continuously pressed together at temperatures above the softening range of the fluoropolymer.

5. Use of a lining laminate according to one of claims 1 to 3 for the inner lining of containers for aggressive media.