DE3415567A1 - ASBEST-FREE, BENDABLE MATERIAL - Google Patents

Description

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The invention relates to a flexible sheet material which is suitable for use in the manufacture of seals, in particular cylinder head gaskets for internal combustion engines.

Such material is usually made up of predominantly asbestos fibers, cellulosic fibers and particles made of barytes (as an oil-resistant filler), all of which are connected with a binder, the usual is an organic polymer. The material is made using conventional paper machines such as one Fourdrinier machine and is actually often called "asbestos paper". In the manufacture of cylinder head gaskets two lengths of asbestos paper (usually 0.3-1.3mm thick) are made from rolls peeled off and with a sheet of metal (e.g. a tin plate), which is to form the support element of the seal in between, pulled between rollers which bring the two paper webs into engagement with the metal sheet, for example by the pressing of flat tongues on the metal sheet into the paper. From the composite web thus formed are then Gasket blanks punched in the desired shape.

The present invention provides non-asbestos based paper, but provides the requisite properties for use as cylinder head gaskets, especially the flexibility and tensile strength for the Further processing for seals without losing the context and the ability to not only protect against cylinder gases, but also to seal against water-based rust inhibitors and against oil. In addition, it is desirable that the gasket should be easily removable from the cylinder head when the head is removed from the cylinder block.

The knot-free, flexible sheet material of the invention is made by ordinary papermaking techniques, however

using an aqueous papermaking slurry of special ingredients that are used in special proportions. The conventional method can do so can be summarized as being an aqueous slurry ^ the various components of the paper gradually as a layer on a water-permeable conveyor base dewatered and the dewatered layer is then pressed and dried. The new aqueous papermaking slurry, which is used in the method of the invention contains the following ingredients in the following amounts share, based on dry weight

Plastic clay 35 - 60%

Cellulose fibers 2-10%

Organic polymer binder 5-20%

Fibrillated poly (aromatic amide)

fibers 10 - 40%

The plastic clay that is used in the unrefined state is the component that makes the finished paper fundamental Cohesion combined with flexibility. In addition, its presence is very supportive of the Formation of a layer of good "green strength" on the

water-permeable conveying pad of the paper machine.

The function of cellulose fibers is mainly in helping to form a web on the water-permeable conveyor bed of the paper machine. the

Cellulose fibers are expediently used with a freeness of 60 - 90 ° Schopper Riegler.

The organic polymer binder is preferably a synthetic rubber, since this improves the flexibility of the finished paper. The synthetic rubber is preferably a

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Nitrile rubber, such as an acrylonitrile-butadiene copolymer, expediently with a butadiene content of 25-75% by weight.

During the production of the paper, the synthetic rubber is distributed or dispersed in the aqueous Slurry introduced, which is gradually dewatered, suitably by using a commercially available one Latex containing a dispersant.

The fibrillated fibers of poly (aromatic amide) or ¹¹ ar amide "aid in the formation of a web, but not as effectively as the cellulose fibers. However, they are much better than cellulose fibers in their ability to withstand high temperatures (280-300 ^° C). A very suitable aramid is poly (p-benzamide) which is available under the trade name Kevlar

used in fibrillated form, that is, with side branches extending from a main stem, and because of their branched nature they are usually fluffy masses or "pulps" of low bulk density, on the order of 0.1 g / cm ³ . Preferably the aramid constitutes at least 20% by weight of the paper and accordingly at least 20% by weight of the solids in the slurry from which the paper is formed.

The sealing properties of the paper against water can be improved by including a wax, such as Paraffin wax, expediently in an amount of 0.5-5% by weight of the paper.

The density of the paper produced is usually in the range of 800-1500 kg / m ³ .

The following example illustrates the invention.

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example

This example shows the production of an asbestos-free sealing paper from an aqueous slurry with a solids content of the following composition:

% Dry weight

Cellulose fibers 5 Fibrillated poly (aromatic

Amide) 32

Plastic clay 49

Rubber 13

Wax 1

A. Preparation of the slurry

i) Lapponia pulp (bleached softwood sulphate pulp) in the form of a gene became an aqueous slurry of about 3% by weight solids content and treated in the disc refiner until the freeness is 80 ° Schopper Riegler cheated.

ii) The pulp of i) (0.5 kg dry weight) was added to 113.5 1 water at 60 ⁰ C in a mixing tank and stirred vigorously, a slurry of the diluted minutes. Then one after the other with vigorous stirring

the following components were introduced:,

Plastic clay: 4.9 kg (91% goes through a sieve of 5 μm

clear mesh size).

Fibrillated poly (aromatic amide): 160 1 one

aqueous suspension containing 2 wt .-% of the material under the designation Kevlar pulp is commercially available.

Paraffin / petrolatum emulsion: (average particle size 1 μπι) 100 g dry weight in 1 1 water.

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Finally, a commercially available aqueous acrylonitrile-butadiene copolymer latex (pH 9.5-12; solids content 30-34%; Acrylonitrile content of the copolymer 33%) diluted with 5 times its own volume Water, added.

iii) The pH of the slurry in the mixer was then lowered to about 4.5 by adding papermaker's alum (aluminum sulfate). The supernatant liquid that remained after the stirring was stopped was clear, indicating that the dispersed rubber particles of the latex were all deposited on the fibers and fillers. Then water of 60 ^° C. was added in order to bring the total volume of the water present to 500 1 and the stirring was continued for 3 min.

B. Making the paper

The above slurry A became completely more common Formed into a pliable sheet material in which a conventional polyacrylamide anionic flocculant and antifoam agent was used by running on a Fourdrinier flatwire paper machine as described in the Chapters 10 and 11 of "Paper and Board Manufacture" by Julius Grant, Jams H. Young and Barry G. Watson, Publisher: Technical Division, The British Paper and Board Industry Federation, London 1978, was processed. The slurry is gradually dewatered as it migrates on the water-permeable conveyor base of the machine and the dewatered material is pressed solidified between rollers. The web material thus formed is dried on heated cylinders, between heated cylinders Calendered pressure rollers (temperature 130 - 150 ° C) and wound on rolls.

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The properties of those obtained from slurry A. two flexible sheet materials were as follows:

Thickness mm 0.49 0.75

Mass / unit area g / m ² 598

Density kg / m ³ 1220 tensile strength

Machine direction MPa 17.5 10.5

Cross direction MPa 14.9 8.8

Compression at 6.89 MPa% 9 »5 ie

Compression recovery % 70

Plastic clay is a fine-grained, highly plastic and mainly kaolinitic sedimentary clay. the Terms "kaolinitic" and "kaolinite" are mineralogical terms and give an indication of the chemical Composition and chemical structure. However, they must not be confused with the term "kaolin", which defines a very refractory clay, which is similar to the mineral koalinite in chemical composition and Approaching structure, which, in contrast to plastic clay, is hardly plastic. Different types of plastic Clays contain varying amounts of kaolin, a mica-like material as well as quartz along with small amounts inorganic materials and other minerals. Plastic clays are mainly used to make pottery and refractory materials used, but not as such, as they show excessive shrinkage, which can be up to 20% when fired, but rather in a mixture with other clays, such as the kaolin mentioned above, so that they become plastic

^ ^w and thus the green strength of the unfired goods is improved. The plasticity of plastic clays for which they are valued is likely due to a combination of fine particle sizes and the presence of colloidal carbonaceous material called

^ΔΌ humic acids, back.

Claims (1)

Patent Attorneys · European Patent Attorney «' Dr. MülIer-ΒθΓέ and Partner ■ POB 2G 02 47 · D-8000 Munich ;; - ;. 341556 -Dr. W. Müller-Bore f Dr. Paul Deuf el Dipl.-Chem., Dipl.-Wirtsch.-Ing. Dr. Alfred Schön Dipl.-Chem. Werner Hertel Dipl.-Phys. Dietrich Lewald Dipl.-Ing. Dr.-Ing. Dieter Otto Dipl.-Ing. D / Sz - T 1581 Z April 8, 1334 T & N Materials Research Limited 20 St. Mary's Parsonage Manchester M3 2N1 England Asbestos-free, flexible material PATENT CLAIMS 1. Asbestos-free, pliable sheet material made by dewatering a layer of aqueous slurry on a water-permeable conveyor base and compressing and drying the drained layer, characterized in that the aqueous slurry used is one comprising the following ingredients in the following proportions, based on dry weight: Plastic clay Cellulose fibers Organic polymer binder Fibrillated poly (aromatic amide) fibers 60%
10%
20% - 40% D-8000 coins 2 POB 26 02 47 Cable: phone non / nn -ι λ pi _ τ Telecopier Infotec 6400 B Tel 5-2 3 4 Ί b t> b- / 1 2. Asbestos-free, flexible sheet material according to claim 1, characterized in that the slurry also a Contains wax. 5 3. Use of the asbestos-free, flexible sheet material according to claim 1 or 2 for seals, in particular attached to a metal support. 4. Seal containing asbestos-free, flexible sheet-10 material according to claim 1 or 2, attached or applied to a metal base.