Sealing material and method of foaming application thereof

Abstract

Objective problems of the present invention are: to provide a sealing material which does not involve flowing after applied, and shows an excellent sealing performance even under severe heat resistance conditions, and also can make good independent cells inside even when used in a foamed condition; and to provide a method of foaming application of the sealing material. As means of solving these objective problems, the sealing material according to the present invention is characterized by comprising an ultraviolet-curable component and an ultraviolet polymerization initiator and having a thermoplastic elastomer (which is not ultraviolet-curable) content of not higher than 5 weight % and comprising an acrylate as the ultraviolet-curable component and having a melt-viscosity at 120° C. in a certain range wherein the acrylate has a glass transition temperature after ultraviolet curing and a weight-average molecular weight in their respective certain ranges; and the method according to the present invention of foaming application of a sealing material is characterized by comprising the steps of: hot-melting the sealing material; mixing nitrogen gas into the melted sealing material under a predefined pressurization; discharging the resultant mixture at a predefined pressure into the air to thus foam the mixture and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and curing this sealing foam by ultraviolet rays.

1 . A sealing material, which comprises an ultraviolet-curable component and an ultraviolet polymerization initiator, wherein in cases where the sealing material further comprises a thermoplastic elastomer which is not ultraviolet-curable, its content is not higher than 5 weight % based on the total amount of resin components, and wherein the sealing material comprises an acrylate as the ultraviolet-curable component in a ratio of not less than 50 weight % based on the total amount of the resin components wherein the acrylate has a weight-average molecular weight of 500 to 50,000 and has a glass transition temperature of −70 to 0° C. after ultraviolet curing, and wherein the sealing material has a melt-viscosity at 120° C. of 1,000 to 50,000 mPa·s. 
     
     
         2 . A sealing material according to  claim 1 , which further comprises an acrylate having a glass transition temperature of not lower than 10° C. before ultraviolet curing as another ultraviolet-curable component. 
     
     
         3 . A method of foaming application of a sealing material, which comprises the steps of: hot-melting the sealing material as recited in  claim 1 ; mixing a pressurized inert gas into the melted sealing material; discharging the melted sealing material containing the pressurized inert gas into the air to thus foam the sealing material and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and irradiating this sealing foam with ultraviolet rays, thus curing the sealing material;
 wherein:   the mixing of the inert gas is carried out by: using nitrogen gas as the inert gas;   
       pressurizing the nitrogen gas into a pressure of 0.01 to 0.1 MPa; and blowing the pressurized nitrogen gas into the sealing material; and
 the applying of the sealing material is carried out at a discharging pressure of 2.7 to 9.7 MPa. 
 
     
     
         4 . A method of foaming application of a sealing material according to  claim 3 , wherein the sealing foam has a foam density of 2 to 5. 
     
     
         5 . A method of foaming application of a sealing material, which comprises the steps of: hot-melting the sealing material as recited in  claim 2 ; mixing a pressurized inert gas into the melted sealing material; discharging the melted sealing material containing the pressurized inert gas into the air to thus foam the sealing material and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and irradiating this sealing foam with ultraviolet rays, thus curing the sealing material;
 wherein:   the mixing of the inert gas is carried out by: using nitrogen gas as the inert gas;   
       pressurizing the nitrogen gas into a pressure of 0.01 to 0.1 MPa; and blowing the pressurized nitrogen gas into the sealing material; and
 the applying of the sealing material is carried out at a discharging pressure of 2.7 to 9.7 MPa. 
 
     
     
         6 . A method of foaming application of a sealing material according to  claim 5 , wherein the sealing foam has a foam density of 2 to 5.