GB2142556A

GB2142556A - Coating of porous substrates

Info

Publication number: GB2142556A
Application number: GB8317280A
Authority: GB
Inventors: James Ronald Holker; Anthony John Grant Sagar; Roy Jeffries
Original assignee: Shirley Institute
Current assignee: Shirley Institute
Priority date: 1983-06-24
Filing date: 1983-06-24
Publication date: 1985-01-23
Also published as: GB8317280D0; GB2142556B

Abstract

Previous attempts to form a coating on textile fabric resulted in the coating material being absorbed into the fabric so that the resultant product was stiff. The present invention provides for non-penetrative coating of textile material by impregnating the textile material with a gel or thickened or viscous polymer solution, coating the impregnated fabric and thereafter removing the gel or polymer from the textile material.

Description

SPECIFICATION Coating of porous substrates This invention relates to the non-penetrative coating of porous substrates and more particularly, but not exclusively, the non-penetrative coating of textile fabrics, formed as gloves, with a water and/or oil resistant coating. The coating can also be heat resistant in order to prevent damage to this protective barrier on touching hot objects.

Gloves or mittens which are intended for wear in very cold environments are usually bulky and do not permit the wearer to perform any but the most basic of manual tasks. Work which requires a degree of dexterity of the individual fingers can only be performed by removing the glove or mitten but there is, obviously, only a limited time that a person can be without protection in such cold conditions.

In order to deal with this problem, it has been proposed that a glove be constructed from a plurality of thin layers of textile fabric rather than one thick layer; several thin layers of fabric, in combination, have more flexibility and a greater capacity to occlude air than one thick layer of equivalent weight.

Thus, the composite glove will permit a higher degree of manual dexterity and provide greater warmth than a glove constructed from a single layer of fabric of equivalent weight. The outer layer of the glove, for many purposes, needs to be coated with a rubber or flexible plastic film to prevent penetration by fluids such as water or oil. In some applications the rubber or plastic film needs to be resistant to heat. Provided that this outer film is thin, and not embedded in the outer fabric layer to any significant extent, it will not seriously impair the overall flexibility of the total glove assembly.

However, on coating the outer textile layer with, for example, a rubber latex by conventional techniques, the open structure of the fabric layers tended to absorb the latex into the interstices thereof. Total penetration of the rubber could not be prevented and the resultant article was very stiff and allowed little free movement of the fingers.

Attempts to prevent the latex from penetrating the fabric by treatment with water repellents have, to-date, been only partly successful. The present invention has been made from a consideration of this problem.

According to the invention there is provided a method of substantially non-penetratively coating a porous substrate by filling the pores with a fluid impervious layer comprising, at least partially impregnating the substrate with a thixotropic gel or a suitably thickened or viscous polymer solution, coating the impregnated substrate with a substance adapted to form an outer layer and, after the said outer layer has formed, removing the thixotropic gel or polymer solution from the substrate.

In a preferred embodiment of the invention the porous substrate is a textile material or fabric, which may be knitted, woven, or non-woven and may consist of one or a plurality of layers, or an article formed therefrom.

impregnation of the substrate with the polymer solution or gel may be substantially complete or partial as desired. For example, for some purposes, limited penetration of the surface layers of the substrate by the coating may be allowable or even desirable.

In a preferred form of the invention the impregnant material is a thixotropic gel of, for example, an organic polymer or a so-called artificial clay. Impregnation is conveniently effected by dipping the substrate in the gel but it can also be carried out by other techniques such as spraying, lick coating, transfer coating, and the like. The substrate may advantageously have a silicone water repellent applied thereto. Although aqueous gels are preferred, gels in organic solvents may also be used.

The outer coating is preferably a fluid impervious layer which can be formed from natural or synthetic rubber or plastics materials by dipping, spraying, lick coating, transfer coating or like process. When the coating has been formed the thixotropic gel or polymer solution is removed from the substrate by washing with water or suitable organic solvent, under agitation. The resulting laminate is then dried when, in the case of the artificiai clay gel, any traces of gel not removed by the washing step will be converted into a non-toxic powder which can be left in situ.

The invention will be further illustrated by reference to the production of a glove.

A knitted woollen glove was placed on a former of suitable dimensions. The former was chosen on the basis that the knitted fabric should not be stretched unduly, in order to keep the fabric pores as small as possible. The glove was then dipped in a thixotropic gel of a synthetic swelling clay marketed as Laponite CP (2% w/v in water containing 0.8 milli-equivalents Na+/g clay). During dipping the gel was agitated to keep its viscosity low. A second woolen glove similar to the first, was fitted over the impregnated first glove and the assembly was again dipped into the gel bath. A third, similar woolen glove was then fitted over the second impregnated glove. The excess gel, which had been forced through the outer layer, was wiped off and the glove assembly flamed to remove surface fibrils. The assembled, gelimpregnated glove was then subjected to a conventional dipping process using nitrile rubber latex to form a fluid impermeable, vulcanised outer coating.

Thereafter the finished composite glove was removed from the former and washed to remove the gel. Finally the product was dried.

Although the invention has been specifically described with reference to the production of gloves it will be understood that it is not limited thereto. The invention can be used for coating any porous substrate where the penetration of the coating into the substrate is to be limited or prevented altogether.

1. A method of substantially non-penetratively coating a porous substrate by filling the pores with a fluid impervious layer comprising at least partially impregnating the substrate with a thixotropic gel or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Coating of porous substrates This invention relates to the non-penetrative coating of porous substrates and more particularly, but not exclusively, the non-penetrative coating of textile fabrics, formed as gloves, with a water and/or oil resistant coating. The coating can also be heat resistant in order to prevent damage to this protective barrier on touching hot objects. Gloves or mittens which are intended for wear in very cold environments are usually bulky and do not permit the wearer to perform any but the most basic of manual tasks. Work which requires a degree of dexterity of the individual fingers can only be performed by removing the glove or mitten but there is, obviously, only a limited time that a person can be without protection in such cold conditions. In order to deal with this problem, it has been proposed that a glove be constructed from a plurality of thin layers of textile fabric rather than one thick layer; several thin layers of fabric, in combination, have more flexibility and a greater capacity to occlude air than one thick layer of equivalent weight. Thus, the composite glove will permit a higher degree of manual dexterity and provide greater warmth than a glove constructed from a single layer of fabric of equivalent weight. The outer layer of the glove, for many purposes, needs to be coated with a rubber or flexible plastic film to prevent penetration by fluids such as water or oil. In some applications the rubber or plastic film needs to be resistant to heat. Provided that this outer film is thin, and not embedded in the outer fabric layer to any significant extent, it will not seriously impair the overall flexibility of the total glove assembly. However, on coating the outer textile layer with, for example, a rubber latex by conventional techniques, the open structure of the fabric layers tended to absorb the latex into the interstices thereof. Total penetration of the rubber could not be prevented and the resultant article was very stiff and allowed little free movement of the fingers. Attempts to prevent the latex from penetrating the fabric by treatment with water repellents have, to-date, been only partly successful. The present invention has been made from a consideration of this problem. According to the invention there is provided a method of substantially non-penetratively coating a porous substrate by filling the pores with a fluid impervious layer comprising, at least partially impregnating the substrate with a thixotropic gel or a suitably thickened or viscous polymer solution, coating the impregnated substrate with a substance adapted to form an outer layer and, after the said outer layer has formed, removing the thixotropic gel or polymer solution from the substrate. In a preferred embodiment of the invention the porous substrate is a textile material or fabric, which may be knitted, woven, or non-woven and may consist of one or a plurality of layers, or an article formed therefrom. impregnation of the substrate with the polymer solution or gel may be substantially complete or partial as desired. For example, for some purposes, limited penetration of the surface layers of the substrate by the coating may be allowable or even desirable. In a preferred form of the invention the impregnant material is a thixotropic gel of, for example, an organic polymer or a so-called artificial clay. Impregnation is conveniently effected by dipping the substrate in the gel but it can also be carried out by other techniques such as spraying, lick coating, transfer coating, and the like. The substrate may advantageously have a silicone water repellent applied thereto. Although aqueous gels are preferred, gels in organic solvents may also be used. The outer coating is preferably a fluid impervious layer which can be formed from natural or synthetic rubber or plastics materials by dipping, spraying, lick coating, transfer coating or like process. When the coating has been formed the thixotropic gel or polymer solution is removed from the substrate by washing with water or suitable organic solvent, under agitation. The resulting laminate is then dried when, in the case of the artificiai clay gel, any traces of gel not removed by the washing step will be converted into a non-toxic powder which can be left in situ. The invention will be further illustrated by reference to the production of a glove. A knitted woollen glove was placed on a former of suitable dimensions. The former was chosen on the basis that the knitted fabric should not be stretched unduly, in order to keep the fabric pores as small as possible. The glove was then dipped in a thixotropic gel of a synthetic swelling clay marketed as Laponite CP (2% w/v in water containing 0.8 milli-equivalents Na+/g clay). During dipping the gel was agitated to keep its viscosity low. A second woolen glove similar to the first, was fitted over the impregnated first glove and the assembly was again dipped into the gel bath. A third, similar woolen glove was then fitted over the second impregnated glove. The excess gel, which had been forced through the outer layer, was wiped off and the glove assembly flamed to remove surface fibrils.The assembled, gelimpregnated glove was then subjected to a conventional dipping process using nitrile rubber latex to form a fluid impermeable, vulcanised outer coating. Thereafter the finished composite glove was removed from the former and washed to remove the gel. Finally the product was dried. Although the invention has been specifically described with reference to the production of gloves it will be understood that it is not limited thereto. The invention can be used for coating any porous substrate where the penetration of the coating into the substrate is to be limited or prevented altogether. CLAIMS

1. A method of substantially non-penetratively coating a porous substrate by filling the pores with a fluid impervious layer comprising at least partially impregnating the substrate with a thixotropic gel or a thickened or viscous polymer solution, coating the impregnated substrate with a substance adapted to form an outer layer and, after the said outer layer has formed removing the thixotropic gel or polymer solution from the substrate.

2. A method as claimed in Claim 1,wherein the porous substrate is a textile material or fabric.

3. A method as claimed in Claim 1 or Claim 2, wherein impregnation of the substrate with the gel or polymer solution is partial.

4. A method as claimed in any preceding claim, wherein impregnation is effected by dipping the substrate in the gel or polymer solution or by coating the substrate with the gel or polymer solution.

5. A method as claimed in any preceding claim, wherein a water repellant is applied to the substrate.

6. A method as claimed in Claim 5, wherein a water repellant is applied to the substrate prior to impregnation.

7. A method as claimed in any preceding claim, wherein the outer layer is fluid impervious.

8. A method as claimed in any preceding claim, wherein the outer layer is formed from natural or synthetic rubber or plastics material.

9. A method as claimed in any preceding claim, wherein the gel or polymer solution is removed from the substrate by washing.

10. A method as claimed in Claim 8, wherein washing is effected with water or an organic solvent.

11. A method of substantially non-penetratively coating a porous substrate substantially as described herein.

12. A porous substrate coated in accordance with the method as claimed in any preceding claim.

13. A glove produced by the method as claimed in any preceding claim.