JPS6258309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to flexible heat resistant articles that are particularly useful as protective barriers during welding.

BACKGROUND OF THE INVENTION Welding metal parts together is a widely practiced operation, especially in heavy industry and shipbuilding. One problem with many welding operations is molten metal flying off the site of the weld and falling into the surrounding area. Removal of cooled metal splatter is difficult and time consuming and has therefore led to the practice of covering surfaces adjacent to the weldment with flexible mats. Typically, mats are made from asbestos or other heat resistant materials such as glass or silica fibers. However, such pine is not completely satisfactory since after a short period of use they weaken due to surface erosion. Repairing pine trees is generally difficult, if not impossible, and expensive.

British Patent No. 962344 discloses a laminate article consisting of a visibly exposed heat-reflecting metal film adhered to a flexible textile backing with a heat absorbing or heat dissipating layer adhered to the back side of the backing. It is listed. This article is intended as a protective thermal shield against high intensity radiant thermal energy.

British Patent No. 760,599 discloses that the flame resistance of heat-vulcanizable silicone rubbers can be improved by incorporating finely divided glass. According to the disclosure of this British patent, it is essential that the glass be used in a finely ground state and it is desirable to use glass frit with an average particle size of less than about 15 microns.

To provide welding covers and protective clothing,
It has also been proposed to coat textile supports such as glass cloth with thermosetting silicone rubber. Although silicone rubber improves the abrasion, tear and puncture resistance of substrates, there was still a need to improve the protection afforded to textiles that withstand contact with extremely hot substances, such as molten metal.

According to the invention there is provided an article for use as a protective cover against hot solid and/or liquid splashes, which covers at least a portion of its surface that is exposed to heated solids and/or liquids during use. It includes a flexible, heat resistant support having an organopolysiloxane elastomer having an inorganic, particulate, cellular filler material incorporated thereon.

The flexible support used to make the articles of the invention can be constructed of any heat resistant material, such as asbestos, carbon fiber, glass fiber, or silica fiber. The support can, for example, take the form of a woven fabric or a blanket of randomly arranged fibers, which are rendered adhesive by the presence of an elastomeric coating.
A preferred support, particularly for welding applications, comprises a mass of random fibers encapsulated within a woven fiber sheath. Typically such a support would be a blanket or a sashimi structure comprising a random fiber batting held between two outer sheets of woven fibers. The outer sheet is sewn or otherwise held separately at its edges.

Organopolysiloxane elastomers that can be used as coatings in the preparation of the articles of this invention are well known materials. Compositions for making such elastomers typically combine units selected from dimethylsiloxane, phenylmethylsiloxane, diphenylsiloxane, 3,3,3-trifluoropropylsiloxane, and methylvinylsiloxane with other dimethylsiloxanes. and one or more curable organosiloxane polymers containing triorganosiloxane units, with or without trimethylsiloxane, dimethylvinylsiloxane and phenylmethylvinylsiloxane units. The silicon-bonded organic substituents present in elastomer-forming organosiloxane polymers are usually selected from methyl, vinyl, phenyl and 3,3,3-trifluoropropyl, although other types of substituents may also be used, e.g. Those skilled in the art will appreciate that their presence is possible depending on the system and properties desired in the elastomer. Other substituents that may be present include higher alkyl groups such as ethyl and 2,4,4-trimethylpentyl, silacyclopentenyl and mercaptoalkyl groups.

Organopolysiloxane elastomers can be thermoset or room temperature curable, the latter being so named because of their ability to go from a fluid uncured state to an elastomeric state at normal ambient or slightly elevated temperatures. Ru. Thus, for example, organosiloxane polymers can be prepared by applying organic peroxides or peresters and heat, by exposure to high radiant energy, or by application of organosiloxane crosslinking agents, with or without siloxane condensation catalysts. It is possible to harden it to Such elastomers are well known in the art and include, for example, British Patent Specification Nos. 760451; 764246; 802355; 841825; 862576;
957255; 975603; 1272705; 1295194; 1296302 and 1409223 and U.S. Patent No. 4052529
It is listed in the issue. In addition to the particulate cellular materials specified, the organopolysiloxane elastomer may, if desired, contain other fillers and additives, such as fume silica, precipitated silica, diatomaceous earth, aluminum hydroxide, magnesium oxide, titanium oxide, zinc oxide and cerium hydroxide. May include. Any such additive with high thermal conductivity, however, is desirably used in the minimum amount consistent with the physical properties required in the elastomer. Desirable organopolysiloxane elastomers can withstand normal ambient temperatures or slightly elevated temperatures;
For example, from a composition that is curable at temperatures between 10°C and 30°C and is desirably flowable, ie, has a viscosity of less than about 100,000 CP at 25°C in its original uncured state. Most preferred are diorganopolysiloxanes containing silicon-bonded vinyl groups, for example in methylvinylsiloxane and/or dimethylvinylsiloxane units, in which silicon-bonded hydrogen atoms are present in the main chain siloxane units and/or in the terminal siloxane units. A silicone elastomer obtained by curing a composition comprising an ocganohydrogenpolysiloxane and a catalyst for the reaction of silicon-bonded vinyl groups and silicon-bonded hydrogen atoms. The catalysts mentioned usually contain platinum in the form of its compounds or complexes, for example chloroplatinic acid or complexes formed from chloroplatinic acid and organosiloxanes having substituents exhibiting olefinic unsaturation. It is also desirable that the organopolysiloxane elastomer be of the flame resistant type. Methods of improving the flame resistance of organopolysiloxane elastomers are known and include platinum compounds (see for example GB 1335619), carbon black and certain inorganic oxides and hydroxides such as fume titanium dioxide. Including contamination.

As particulate cell fillers in the elastomeric coating it is possible to use unicellular materials, preferably glass or silica microspheres (microscopic hollow spheres), or multicellular materials such as expanded vermiculite and perlite. be. The particle size of the filler is not strictly critical. The preferred particle size range is from about 20 to about 500 microns, but smaller or larger particle sizes, such as up to 2000 microns, can also be used. Preferably
20 to 110 parts by weight of cell filler are used in the elastomer per 100 parts by weight of curable organosiloxane polymer. Higher proportions of filler can be used, however, if the resulting loss of elasticity can be tolerated. The cellular filler can be incorporated into the organopolysiloxane elastomer-forming composition by any suitable procedure that avoids destruction of the cellular features of the filler. When the fillers include hollow microspheres, they are conveniently incorporated into the liquid elastomer-forming composition by stirring or other simple mixing procedures.

Any suitable technique can be used to form the organopolysiloxane elastomer coating on the flexible support, such as knife coating or brush coating. If desired, it is possible to apply the elastomer-forming composition as a dispersion in a diluent. Following application of the elastomer-forming composition to a support, the elastomer-forming composition may be prepared in any suitable manner;
It can be cured, for example, by exposure to heat or radiation or by exposure to atmosphere at normal ambient temperatures. The thickness of the cured elastomer applied to the support will depend on considerations such as weight, cost, and severity of working conditions. However, generally the thickness of the elastomer coating is 50
It is desirable that it be within the range of -2000 microns.

The article of the invention is particularly suitable for improved welding mats used to protect surfaces surrounding welding operations from molten metal splash. However, they are also useful in other applications requiring the provision of flexible heat resistant protection.

The following examples further illustrate the invention, all parts being expressed by weight.

Example 1 A silicone elastomer-forming composition was made by mixing together the following: Polydimethylsiloxane with vinyl groups attached to each terminal Si (viscosity 400 cS at 25°C)
48.5 parts Trimethylsiloxy-terminated methylhydrogen polysiloxane 2.8 parts Crushed quartz 48.5 parts Platinum catalyst (complex of chloroplatinic acid and low molecular weight vinyl siloxane) 0.16 parts Silica microscopic hollow spheres (300 microns) 40 parts Twill glass in it The composition was applied by knife application to one surface of a welded mat containing a sashiko made from a mat of randomly oriented glass fibers contained within a fiber envelope. The organopolysiloxane was cured at room temperature for about 24 hours to produce a flexible elastomeric coating having a thickness of about 1.0 mm. It has been found that when this mat is used as a protective cover in close proximity to an electric arc welding operation, many droplets of molten metal are blown off without damaging the protective mat. The splattered metal left on the pine caused some erosion of the elastomeric coating, but did not destroy the fibrous structure of the pine. Damage to the elastomeric surface could be easily repaired by reapplication.

Example 2 Expanded vermicrite (15 parts) consisting of particles having dimensions ranging from about 5 microns to about 2000 microns was incorporated by stirring into an elastomer-forming composition containing the following ingredients: Polydimethylsiloxane with vinyl group bonded to Si atom (2500cS at 25℃)
45 parts trimethylsiloxy-terminated methylhydrogen polysiloxane 3.5 parts surface-treated fume silica 18 parts titanium dioxide 5 parts platinum catalyst (as in Example 1) 0.18 parts The composition was then prepared for welding as described in Example 1. It was applied to the pine surface and cured for 24 hours at normal ambient temperature. The rubbery coating formed on the welding mat had a thickness of approximately 1.5 mm. The mats performed similarly to those made according to Example 1 when tested in close proximity to arc welding operations as protective covers. An elastomer-forming composition as described in Example 1 was applied where the elastomer-forming composition was applied in two separate coats to the surface of the pine and also over the first coating except for the silica microhollow spheres. A similar behavior was obtained in the case of

Claims (1)

Claims: 1. A flexible material having a coating of organopolysiloxane elastomer on at least a portion of the surface exposed to hot solids and/or liquids during use;
It consists of a heat-resistant fibrous support, and the organopolysiloxane contains inorganic particles,
Article for use as a protective covering against hot solid and/or liquid splashes, characterized in that it contains a foam-like substance. 2. The article of claim 1, wherein the organopolysiloxane elastomer is a cured product of a room temperature-curable organopolysiloxane composition. 3. The curable organopolysiloxane composition comprises a mixture of a diorganopolysiloxane having silicon-bonded vinyl groups, an organohydrogenpolysiloxane, and a catalyst for the reaction of the silicon-bonded vinyl groups with the silicon-bonded hydrogen atoms. Article according to claim 2. 4. The article according to claim 3, wherein the catalyst contains platinum.