JP2009280640A - Sealing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing material having flexibility even in a highly compressed state and having excellent water cut-off property. <P>SOLUTION: The sealing material includes a sheet-like resin foam of an open cell structure or a semi-open, semi-closed cell structure, wherein the upper and under surfaces of the sealing material are not subjected to water cut-off treatment by melting and the whole lateral face is subjected to water cut-off treatment by melting. The water cut-off treatment by melting is preferably melt-solidification treatment of the resin using laser irradiation. The sealing material preferably has a water cut-off layer on at least one of the upper and under surfaces. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealing material composed of a sheet-like resin foam. More specifically, the present invention relates to a sealing material made of a sheet-like resin foam used for electronic equipment and the like for the purpose of sealing water-stopping and other liquid substances, and having the entire side surface subjected to a melt water-stopping treatment.

  Conventionally, sealing materials used in electronic devices are required to have functions such as shock-absorbing property, dust-proofing property, and shock-absorbing property. However, along with the usage environment of the target electronic device, the device itself is often required to be waterproof, and the sealing material is also required to be waterproof.

  Conventionally, foams having a closed cell structure (see Patent Document 1), unfoamed rubber sheets, and the like have been used as sealing materials that require water-stopping. However, in electronic devices that tend to be thinner, the clearance (gap) in which the seal material is used is small, and it is necessary to use the seal material with high compression. These seal materials have a large repulsive force during compression. It was difficult to use at high compression.

  Furthermore, since it is necessary to use the sealing material at high compression, it is desirable to use a foamed sealing material having an open cell structure / semi-continuous semi-independent structure that has flexibility even in a highly compressed state. The foam sealing material having a structure / semi-continuous semi-independent structure has a low water-stopping property.

JP 2005-263963 A

  Accordingly, an object of the present invention is to provide a sealing material that can have flexibility even in a highly compressed state and has excellent water-stopping properties.

  As a result of intensive studies to solve the above problems, the present inventor has made a sealing material composed of a sheet-like resin foam having an open cell structure or a semi-continuous semi-independent structure, and a melt water-stop treatment on the upper surface and the lower surface. It is found that if the melt-stop treatment is applied to the entire side surface without applying, the flexibility can be maintained even in a highly compressed state, and the water-stop performance as a sealing material can be improved, and the present invention is completed. I let you.

  That is, the present invention is a sealing material constituted by a sheet-like resin foam having an open cell structure or a semi-continuous semi-independent structure, the upper surface and the lower surface are not melt-sealed, and the entire side surface is melt-stopped. Provided is a sealing material characterized by being treated with water.

  It is preferable that the melt water-stopping treatment is a resin solidification treatment using laser irradiation.

  It is preferable that the sealing material further has a water stop layer on at least one of the upper surface and the lower surface. Moreover, it is preferable to have a skin layer, a coat layer, and an adhesive layer as a water-stopping layer. A resin layer is preferable as the coating layer.

The sealing material preferably has a water absorption rate of less than 450 wt%, and preferably has a 50% compression repulsion force of 5.5 N / cm ² or less.

  The present invention further provides an adhesive sealing material having a configuration in which an adhesive layer is provided on at least one surface of the sealing material.

  According to the sealing material of the present invention, since it has the above-described configuration, the flexibility can be maintained even in a highly compressed state, and the entire side surface subjected to the melt-stop treatment is sealed against water and other liquid substances. Demonstrates water-stopping properties and can exhibit good water-stopping performance as a sealing material.

  The sealing material (sealing material) of the present invention is a sealing material constituted by a sheet-like resin foam having an open cell structure or a semi-continuous semi-independent structure, and the upper surface and the lower surface are not melt-stopped, and The entire side surface is melt-stopped. That is, the side surface of the sealing material of the present invention is a molten water-stopped surface in which the entire side surface is melt-waterproofed. Such a melt-stop surface exhibits sealing properties against gases such as air, nitrogen, oxygen, carbon dioxide and water vapor, water and other liquid substances (for example, alcohols), and solids such as dust.

  For this reason, the sealing material of the present invention is good in addition to the buffering properties, dustproof properties, shock absorption properties, airtightness, soundproofing properties, heat insulating properties, etc., inherently possessed by the sealing material made of a sheet-like resin foam. Has water-stop (water-stop effect).

  The sealing material of the present invention is used after being processed (for example, cutting, punching, etc.) into a predetermined shape (for example, a quadrangular prism shape, a window frame shape, an L shape, etc.) according to the shape of the clearance. May be.

(Sheet-like resin foam)
The sheet-like resin foam is a resin foam having an open-cell structure or semi-continuous semi-independent structure constituting the sealing material of the present invention, and has a sheet-like form and a cell structure having an open-cell structure or semi-continuous semi-independent structure ( For example, the upper surface and / or the lower surface (front surface and / or rear surface) may have a water blocking layer that is a layer that exhibits water blocking properties against water and other liquid substances. .

  The semi-continuous and semi-closed cell structure is a cell structure in which a closed cell structure and an open cell structure are mixed, and normally, the closed cell structure occupies 30% or less (preferably 20% or less) of the entire cell structure. Means structure. The closed cell structure means a structure in which individual cell structures are independent, and the open cell structure means a structure in which bubbles are communicated.

  That is, the sheet-like resin foam in the sealing material of the present invention has a cell structure with an open cell rate of at least 70% (preferably 80%). The open cell rate is defined as follows.

The specific gravity and mass (Wa) of the sheet-like resin foam are measured. Next, the sheet-like resin foam is submerged in water in a container placed in a vacuum container, and the inside of the vacuum container is decompressed to 10 mmHg or less in that state. After decompression, the inside of the vacuum container is returned to normal pressure and left for 5 minutes to allow the sheet-like resin foam to absorb water. In the state of water absorption, the weight (Wb) of the sheet-like resin foam is measured, and the open cell ratio is defined from the following formula.
Open cell ratio (%) = [(Wb−Wa) / specific gravity of water (1.00)] / [1- (specific gravity of sheet-like resin foam) / (specific gravity of sheet-like resin foam before foaming) × (Wa) / specific gravity of sheet-like resin foam] × 100

  Since the sheet-like resin foam thus has an open cell structure or a semi-continuous semi-independent cell structure, it has high stress relaxation properties and can maintain flexibility even in a highly compressed state. Therefore, the sealing material of the present invention can be used for a minute clearance (for example, a clearance of about 0.10 to 0.20 mm) (hereinafter sometimes referred to as “minute clearance”).

  The sheet-like resin foam can be obtained by a method used in ordinary foam molding such as a physical method or a chemical method.

  The chemical method is a method of obtaining a foam by forming cells with a gas generated by thermal decomposition of a compound (foaming agent) added to a polymer base. In this foaming method, since the residue of the foaming gas remains in the foam, the contamination by the corrosive gas and impurities in the gas becomes a problem particularly in the electronic device application where the demand for low contamination is high. There is a problem that it is difficult to form a fine bubble structure (particularly, a fine bubble of 300 μm or less).

  The physical method is a foam molding method in which a low boiling point liquid (foaming agent) is dispersed in a polymer and then heated to volatilize the foaming agent to form bubbles. In this foaming method, depending on the substance used as the foaming agent, there is a concern about the impact on the environment such as flammability and toxicity of the substance and ozone layer destruction.

  For example, when a low-boiling liquid such as chlorofluorocarbons or hydrocarbons is used as a foaming agent, problems such as flammability and toxicity of the above-mentioned substances and adverse effects on the environment such as ozone layer destruction, There is a problem that it is difficult to form a bubble structure (particularly, fine bubbles of 300 μm or less).

  For this reason, in this invention, since the cell diameter is small and a foam with a high cell density is obtained, the physical foaming method using a high pressure inert gas as a foaming agent is used suitably. Moreover, if a physical foaming method using a high-pressure inert gas (particularly carbon dioxide) as a foaming agent is used, a clean resin foam with few impurities can be obtained.

  In the present invention, the thermoplastic polymer that is the material of the sheet-like resin foam is not particularly limited as long as it can form a cell structure by a physical foaming method using a high-pressure inert gas as a foaming agent. Density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, copolymers of ethylene and propylene, copolymers of ethylene or propylene and other α-olefins, ethylene and other ethylenic polymers Olefin polymers such as copolymers with saturated monomers (for example, vinyl acetate, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, vinyl alcohol, etc.); polystyrene, acrylonitrile-butadiene-styrene copolymer Styrenic polymers such as (ABS resin); 6-Niro , 66-nylon, 12-nylon, etc. polyamide; polyamideimide; polyurethane; polyimide; polyetherimide; acrylic resin such as polymethyl methacrylate; polyvinyl chloride; polyvinyl fluoride; alkenyl aromatic resin; Polyester such as terephthalate; polycarbonate such as bisphenol A-based polycarbonate; polyacetal; polyphenylene sulfide.

  The thermoplastic polymer includes a thermoplastic elastomer that exhibits properties as a rubber at room temperature and exhibits thermoplasticity at a high temperature. Examples of such thermoplastic elastomers include olefin elastomers such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, and chlorinated polyethylene; Styrenic elastomers such as butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-isoprene-butadiene-styrene copolymers, and hydrogenated polymers thereof; thermoplastic polyester elastomers; thermoplastic polyurethane elastomers A thermoplastic acrylic elastomer and the like. These thermoplastic elastomers, for example, have a glass transition temperature of room temperature or lower (for example, 20 ° C. or lower), so that they are remarkably excellent in flexibility and shape followability when used as a waterproof material or a sealing material.

  A thermoplastic polymer can be used individually or in mixture of 2 or more types. As the foam material (thermoplastic polymer), any of thermoplastic elastomers, thermoplastic polymers other than thermoplastics, and mixtures of thermoplastic elastomers and thermoplastic polymers other than thermoplastic elastomers can be used.

  Examples of the mixture of the thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer include a mixture of an olefin elastomer such as an ethylene-propylene copolymer and an olefin polymer such as polypropylene. When a mixture of a thermoplastic elastomer and a thermoplastic polymer other than the thermoplastic elastomer is used, the mixing ratio is, for example, the former / the latter = 1/99 to 99/1 (preferably about 10/90 to 90/10, More preferably, it is about 20/80 to 80/20).

  The inert gas used in the present invention is not particularly limited as long as it is inert with respect to the thermoplastic polymer and can be impregnated, and examples thereof include carbon dioxide, nitrogen gas, and air. These gases may be mixed and used. Of these, carbon dioxide, which has a large amount of impregnation into the thermoplastic polymer used as the material of the foam and has a high impregnation rate, is particularly suitable.

  The inert gas when impregnating the thermoplastic polymer is preferably in a supercritical state. In the supercritical state, the solubility of the gas in the thermoplastic polymer is increased, and a high concentration can be mixed. In addition, when the pressure drops suddenly after impregnation, since the concentration is high as described above, the generation of bubble nuclei increases, and the density of bubbles formed by the growth of the bubble nuclei is large even if the porosity is the same. Therefore, fine bubbles can be obtained. Carbon dioxide has a critical temperature of 31 ° C. and a critical pressure of 7.4 MPa.

  When forming a foam, you may add an additive to a thermoplastic polymer as needed. The kind of additive is not particularly limited, and various additives usually used for foam molding can be used. Examples of such additives include cell nucleating agents, crystal nucleating agents, plasticizers, lubricants, colorants (pigments, dyes, etc.), shrinkage inhibitors, ultraviolet absorbers, antioxidants, anti-aging agents, fillers, Reinforcing agents, flame retardants, antistatic agents, surfactants, vulcanizing agents, surface treating agents and the like can be mentioned. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles, and the addition amount used for molding a thermoplastic polymer such as a normal thermoplastic elastomer can be adopted.

  The lubricant has the effect of improving the fluidity of the thermoplastic polymer and suppressing the thermal deterioration of the polymer. The lubricant used in the present invention is not particularly limited as long as it exhibits an effect on improving the fluidity of the thermoplastic polymer. For example, hydrocarbon-based lubricants such as liquid paraffin, paraffin wax, microwax and polyethylene wax; Fatty acid type lubricants such as stearic acid, behenic acid, 12-hydroxystearic acid; ester type lubricants such as butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate

  The anti-shrinkage agent has a function of effectively suppressing permeation of the foaming agent gas by forming a molecular film on the surface of the foam film of the foam. The shrinkage preventing agent used in the present invention is not particularly limited as long as it exhibits an effect of suppressing the permeation of the foaming agent gas, and examples thereof include fatty acid metal salts, fatty acid amides, and fatty acid bisamides.

  As a method for producing a foam by impregnating a thermoplastic polymer with a high-pressure inert gas, specifically, a gas impregnation step of impregnating a thermoplastic polymer with an inert gas under high pressure, the step Examples of the method include a decompression step in which the pressure is lowered later to foam the resin, and a heating method in which bubbles are grown by heating as necessary. In this case, an inert gas may be impregnated with a pre-molded unfoamed molded product, or the molten thermoplastic polymer is impregnated with an inert gas under pressure and then subjected to molding during decompression. May be. These steps may be performed by either a batch method or a continuous method.

  According to the batch method, for example, a foam can be formed as follows. That is, first, an unfoamed molded article (such as a resin sheet for foam molding) is obtained by extruding a thermoplastic polymer such as a polyolefin resin or a thermoplastic elastomer using an extruder such as a single screw extruder or a twin screw extruder. Form. Alternatively, using a kneading machine equipped with rollers, cams, kneaders, and Banbury type blades, a thermoplastic polymer such as polyolefin resin and thermoplastic elastomer is kneaded uniformly, and this is used with a hot plate press. Then, an unfoamed molded product (such as a resin sheet for foam molding) containing a thermoplastic polymer as a base resin is formed. Then, the obtained unfoamed molded product is put in a pressure vessel, a high-pressure inert gas is introduced, and the inert gas is impregnated in the unfoamed molded product. In this case, the shape of the unfoamed molded product is not particularly limited, and may be any of a roll shape, a plate shape, and the like. The introduction of the high-pressure inert gas may be performed continuously or discontinuously. When impregnated with a sufficiently high-pressure inert gas, the pressure is released (usually up to atmospheric pressure), and bubble nuclei are generated in the base resin. The bubble nuclei may be grown as they are at room temperature, or may be grown by heating as necessary. As a heating method, a known or conventional method such as a water bath, an oil bath, a hot roll, a hot air oven, a far infrared ray, a near infrared ray, or a microwave can be adopted. After the bubbles are grown in this way, the shape is fixed rapidly by cooling with cold water or the like.

  On the other hand, according to a continuous system, a foam can be formed as follows, for example. That is, the thermoplastic polymer is injected with a high-pressure inert gas while kneading the thermoplastic polymer using an extruder such as a single screw extruder or a twin screw extruder, and the thermoplastic polymer is sufficiently impregnated in the thermoplastic polymer, and then extruded. The pressure is released (usually up to atmospheric pressure), foaming and molding are performed simultaneously, and in some cases, the bubbles are grown by heating. After the bubbles are grown, the shape is fixed rapidly by cooling with cold water or the like.

  In addition, when the shape of the resin foam formed by the batch method or the continuous method is not a sheet shape (for example, an annular shape), the resin foam is usually cut into a sheet shape.

  The pressure in the gas impregnation step is, for example, 6 MPa or more (for example, about 6 to 100 MPa), preferably 8 MPa or more (for example, about 8 to 100 MPa). When the pressure is lower than 6 MPa, the bubble growth at the time of foaming is remarkable, the bubbles become too large, and a small average cell diameter (average bubble diameter) in the above range cannot be obtained, and the effect is lowered. This is because, when the pressure is low, the amount of gas impregnation is relatively small compared to when the pressure is high, and the number of bubble nuclei formed is reduced due to a decrease in the bubble nucleus formation rate. This is because the bubble diameter becomes extremely large. Further, in the pressure region lower than 6 MPa, the bubble diameter and the bubble density change greatly only by slightly changing the impregnation pressure, so that it is difficult to control the bubble diameter and the bubble density.

  The temperature in the gas impregnation step varies depending on the type of inert gas and thermoplastic polymer used, and can be selected within a wide range. In consideration of operability and the like, for example, the temperature is about 10 to 350 ° C. For example, the impregnation temperature when impregnating an unfoamed molded article such as a sheet with an inert gas is about 10 to 200 ° C., preferably about 40 to 200 ° C. in a batch system. Further, the impregnation temperature in the case of simultaneously performing foaming and molding by extruding a molten polymer impregnated with gas is generally about 60 to 350 ° C. in the continuous type.

  Among these, when carbon dioxide is used as the inert gas, the temperature during impregnation is preferably 32 ° C. or higher, particularly 40 ° C. or higher in order to maintain a supercritical state.

  In the decompression step, the decompression speed is not particularly limited, but is preferably about 5 to 300 MPa / second in order to obtain uniform fine bubbles. Moreover, the heating temperature in the said heating process is about 40-250 degreeC, for example, Preferably it is about 60-250 degreeC.

  In addition, according to such a method for producing a sheet-like resin foam, a sheet-like resin foam having a high expansion ratio can be produced, and thus there is an advantage that a thick sheet-like resin foam can be produced. . For example, in the case of producing a resin foam by a continuous method, in order to maintain the pressure inside the extruder in the kneading and impregnation step, the gap of the die attached to the tip of the extruder is as narrow as possible (usually 0.1 to 1.. 0 mm). Therefore, in order to obtain a thick resin foam, the resin foam composition extruded through a narrow gap has to be foamed at a high magnification, but conventionally, it is formed because a high foaming ratio cannot be obtained. The thickness of the foam has been limited to a thin one (for example, about 0.5 to 2.0 mm). On the other hand, a resin foam produced using a high-pressure inert gas can continuously obtain a foam having a final thickness of 0.50 to 5.00 mm. In order to obtain such a thick resin foam, the relative density of the resin foam (density after foaming / density in an unfoamed state) is 0.02 to 0.3 (preferably 0.05 to 0). .25) is desirable. When the relative density exceeds 0.3, foaming is insufficient, and when the relative density is less than 0.02, the strength of the foam may be remarkably lowered.

In the present invention, the apparent density of the sheet-like resin foam can be appropriately set according to the purpose of use, but is 0.2 g / cm ³ or less (preferably 0.15 g / cm ³ or less, more preferably 0). .13 g / cm ³ or less). In addition, as a minimum of the apparent density of a sheet-like resin foam, it is preferable that it is 0.02 g / cm < ³ > or more (preferably 0.03 g / cm < ³ > or more). The apparent density of the sheet-like resin foam can be controlled by adjusting the expansion ratio by the amount of inert gas to be impregnated and the pressure. Further, by appropriately adjusting the resin temperature in the decompression step, it is possible to control a foam structure such as a closed cell structure or an open cell structure of the sheet-like resin foam, or a cell structure in which these are mixed. When the apparent density of the sheet-like resin foam exceeds 0.20 g / cm ³ , foaming is insufficient, while when it is less than 0.02 g / cm ³ , the strength of the sheet-like resin foam is significantly reduced. Is not preferable.

The apparent density of the sheet-like resin foam is determined by punching the sheet-like resin foam with a punching blade type of 40 mm × 40 mm and measuring the size of the punched sample. Further, the thickness is measured with a 1/100 dial gauge having a measurement terminal diameter (φ) of 20 mm. The volume of the sheet-like resin foam is calculated from these values. Next, the weight of the sheet-like resin foam is measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the apparent density (g / cm ³ ) of the sheet-like resin foam is calculated.

  The thickness of the sheet-like resin foam is not particularly limited, and can be appropriately selected according to the shape and size of the minute clearance. For example, it can be selected from a range of about 0.5 to 5 mm (preferably 0.8 to 3 mm).

  The average cell diameter (average cell diameter) of the sheet-like resin foam, the repulsive load when compressed, the apparent density, the cell structure, etc. are the type of inert gas and thermoplastic polymer or thermoplastic elastomer used, the additive used, It can be adjusted depending on the production method and the foaming conditions at the time of production. For example, it can be adjusted by appropriately selecting and setting operating conditions such as temperature, pressure and time in the gas impregnation step, operating conditions such as pressure reduction speed, temperature and pressure in the pressure reducing step, heating temperature after pressure reduction, and the like.

  Note that the sheet-like resin foam produced by such a method is a sheet-like resin foam having skin layers on the upper and lower surfaces because air escapes from the thermoplastic polymer during production.

(Melting water stop treatment)
The melt-stopping treatment is a treatment applied to the entire side surface of the sheet-like resin foam, and the entire side surface of the sheet-like resin foam is applied to solids such as gas, water, other liquid substances, and dust by melting and solidifying the resin. This is a process for imparting sealing properties.

  When the surface of the entire side surface of the sheet-shaped resin foam is subjected to a melt-stop treatment that involves melting and solidifying the resin, the cell structure disappears on the entire surface of the side surface of the sheet-shaped resin foam, and a continuous resin structure is formed. The For this reason, the water stop property is exhibited on the side surface subjected to the melt water stop treatment. In the present invention, the portion where the cell structure on the side surface of the sheet-like resin foam disappears and the continuous structure of the resin is formed by the melt water-stop treatment may be referred to as a “melt-water stop treatment portion”. .

  The melt-stop treatment is not particularly limited as long as it is a process that causes the resin to melt and solidify.For example, a process that causes the resin to melt and solidify using a heated metal blade, or a resin that melts and solidifies using laser irradiation. Processing to be generated is included. More specifically, for example, (i) the sheet-like foam is punched with a heated metal blade and the side surface is melted to cause melting and solidification of the resin; (ii) the sheet-like foam Further, it is possible to irradiate a laser from the upper surface or the lower surface and melt the side surface by cutting into a predetermined shape to cause the resin to melt and solidify.

  In particular, in the method using the heated metal blade as in (i) above, the side surface of the sheet-like resin foam and the metal blade are sticky or stuck due to the melting of the resin, and resin sagging occurs. In addition, since the resin adheres and remains on the metal blade, there may be a problem in workability, or there may be an adverse effect on the form of the sealing material. A method using a laser as in ii) is preferred. In addition, the method using the laser as described in (ii) is advantageous compared to the method using a heated metal blade in that it can perform more precise processing and processing speed.

The laser beam used in the method using a laser as described in (ii) above is not particularly limited, and various conventionally known ones can be employed. For example, third or fourth harmonic of ArF excimer laser, KrF excimer laser, XeCl excimer laser, YAG laser, etc., third harmonic or fourth harmonic of solid laser of YLF or YVO ₄ , Ti: S laser A semiconductor laser, a fiber laser, a carbon dioxide gas laser, or the like can be used. Of these laser beams, the semiconductor laser has a wavelength in the infrared region, has high uniformity of power density in the laser spot surface, and is preferable in terms of improving processing accuracy.

  The condensing diameter (spot diameter) of the laser beam can be appropriately set according to the type of processing applied to the sheet-shaped resin foam, but in the case of the cutting process (ii) above, by adjusting the condensing diameter, It is possible to control the cutting width and the thickness in the direction from the side surface to the center of the melt water-stopping treatment portion (the portion where the melt water-stop treatment is performed on the sealing material side surface). The condensing diameter (cutting width) is usually preferably 2 mm to 0.5 mm, more preferably 1.0 mm to 0.5 mm. If the light collection diameter is less than 0.5 mm, it may be difficult to control the power density minutely. On the other hand, if it exceeds 2.0 mm, fine processing may be difficult.

  In the present invention, the “thickness of the melt-stopped portion” means the thickness in the direction from the side surface toward the center. In the present invention, the thickness in the direction from the upper surface to the lower surface (the direction from the lower surface to the upper surface) of the molten water-stopping treatment section is usually the direction from the upper surface to the lower surface of the entire sealing material (the direction from the lower surface to the upper surface). The thickness is the same.

  The power density of the laser beam can be appropriately set according to the physical properties and cutting speed of the sheet-like resin foam. The light absorption rate of the sheet-like resin foam depends on the wavelength of the laser beam. Laser light can oscillate in wavelength from ultraviolet to near infrared by selecting an oscillation medium or crystal. Therefore, by using a laser beam that matches the light absorption wavelength of the sheet-like resin foam, it can be efficiently processed at a low power density. For example, in the case of forming a molten water-stopping treatment part by melting a side surface while irradiating a laser beam from the upper surface or the lower surface of a sheet-like foam and cutting into a predetermined shape, the laser density is 1000 to 2000 W (preferably Is 1500 to 2000 W).

  The thickness of the melt water-stopping treatment part is the thickness in the direction from the side surface toward the center, and is usually 10 to 100 μm (preferably 10 to 30 μm). If the thickness is less than 10 μm, the melt water-stopping treatment part may be damaged when used as a sealing material, resulting in a decrease in water-stopping performance. The seal performance may be adversely affected.

  In addition, since the thickness of the melt water-stopping treatment part exhibits water-stopping properties and is not particularly limited as long as it does not adversely affect the sealing performance of the sealing material, by the side surface of the sealing material or by the site on the same side surface of the sealing material, The thickness may be different or the same.

(Water stop layer)
The water-stopping layer is a layer exhibiting water-stopping provided on the upper surface and / or the lower surface of the sealing material, and is usually provided on both the upper surface and the lower surface from the viewpoint of obtaining good water-stopping properties as a sealing material.

  As the water blocking layer, a skin layer or a coat layer is preferable. Further, the water stop layer may be a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer). Since the water-stopping layer may have a single-layer structure or a laminated structure, the water-stopping layer may be, for example, a water-stopping layer having a laminated structure in which a coat layer is provided on the skin layer, or a skin layer. Alternatively, a water-stopping layer having a laminated structure in which an adhesive layer is provided on the coating layer may be used. In the sealing material having the water stop layer having such a laminated structure, there are, for example, an advantage that the thickness of the coating layer can be reduced and an advantage that the strength of the sealing material can be improved.

  The thickness of the water-stopping layer (thickness in the direction from the upper surface to the lower surface) is not particularly limited as long as the water-stopping property is exhibited on the surface of the layer, but usually the thickness of the entire sealing material (thickness in the direction from the upper surface to the lower surface) Occupying a thickness of 40% or less (preferably 30% or less). Since the water-stopping layer is harder than the foam layer (foam layer) in the sealing material, if it exceeds 40% of the total thickness of the sealing material, flexibility (softness) as the sealing material This is because there is a possibility that followability with respect to clearance may be deteriorated.

  For example, the thickness of the water blocking layer in the sealing material having the water blocking layer on the upper surface and the lower surface is such that the combined thickness of both water blocking layers is within the above range with respect to the thickness of the entire sealing material. It is preferable to occupy. Further, if the thickness of the water-stopping layer is different between the upper surface and the lower surface, it may adversely affect the sealing function of the sealing material, and it is preferable that the thickness is the same on the upper surface and the lower surface. The thickness of the water-stopping layer is 20% or less (preferably 15% or less) with respect to the thickness of the entire sealing material (thickness in the direction from the upper surface to the lower surface).

  The thickness of the water-stopping layer (thickness in the direction from the upper surface to the lower surface) is not particularly limited as long as the water-stopping property is exhibited on the surface of the layer, but from the viewpoint of enhancing the sealing effect of the air bubbles, the cell structure portion inside the sealing material It is preferable to be larger than the average bubble diameter of the bubbles.

  The skin layer is a layer having a high density on the upper surface and the lower surface, which is generated when a sheet-shaped resin foam is produced. The layer includes a portion containing a large amount of unfoamed portions (expanding ratio is extremely high). The lower part). In the skin layer, there is almost no bubble structure, and even if it is present, the expansion ratio is extremely small. Therefore, most of the skin layer is composed of an unfoamed portion (continuous structure) of the resin. For this reason, the skin layer exhibits water-stopping properties on the layer surface.

  When the sealing material has a skin layer, the strength is further improved.

  The coat layer is a layer formed by applying a resin, and is a layer that exhibits water blocking properties on the surface of the layer. When a coating layer is provided on the sealing material, strength and design properties are improved.

  The resin for forming such a coat layer is not particularly limited, and either a thermosetting resin or a thermoplastic resin may be used. Moreover, resin can be used individually or in combination of 2 or more types.

  Examples of the thermosetting resin include phenol resin, amino resin, unsaturated polyester resin, epoxy resin, polyurethane resin, silicone resin, and thermosetting polyimide resin.

  Examples of the thermoplastic resin include low density polyethylene, linear polyethylene, medium density polyethylene, high density polyethylene, ultra low density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, and polymethylpentene. Polyolefin, ethylene-vinyl acetate copolymer, ionomer resin, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, ethylene- Hexene copolymer, Polyester such as polyurethane, polyethylene terephthalate, polyethylene naphthalate, (meth) acrylic polymer, polystyrene, polycarbonate, polyimide, polyamide, polyamideimide, polyether Bromide, polysulfone, polyether sulfone, polyvinyl chloride, polyvinylidene chloride, fluorine resins, cellulose resins, and the like polymers such as those crosslinked like.

  In particular, as the resin for forming the coating layer, a thermoplastic elastomer resin is preferably used because a resin having a large stress relaxation property is preferable in order to prevent adverse effects on flexibility as a sealing material. That is, as the coat layer, a thermoplastic elastomer resin layer is preferable.

  As a thermoplastic elastomer resin, it can select suitably from well-known thermoplastic elastomer resins. The thermoplastic elastomer resin is usually composed of a hard segment portion and a soft segment portion. Specifically, for example, when the thermoplastic elastomer resin is a styrene-isoprene-styrene thermoplastic elastomer resin, a repeating unit (monomer unit or constituent unit) by a styrene component in the styrene-isoprene-styrene thermoplastic elastomer resin. ) Corresponds to the hard segment portion, and the repeating unit of the isoprene component corresponds to the soft segment portion. In the present invention, the ratio of the hard segment portion and the soft segment portion in the thermoplastic elastomer resin is not particularly limited, but the content ratio of the hard segment portion in the thermoplastic elastomer resin may be less than 50 mol%. Particularly preferred is less than 30 mol%. If a thermoplastic elastomer resin having a hard segment content of less than 50 mol% is used as the thermoplastic elastomer resin, the adverse effect on the flexibility of the sealing material can be more effectively suppressed or prevented.

  Specifically, the thermoplastic elastomer resin includes, for example, a styrene thermoplastic elastomer resin, an olefin thermoplastic elastomer resin, a polyester thermoplastic elastomer resin, a polyamide thermoplastic elastomer resin, a urethane thermoplastic elastomer resin, a chloride Examples thereof include vinyl thermoplastic elastomer resins and diene thermoplastic elastomer resins. As the thermoplastic elastomer resin, in particular, a styrene thermoplastic elastomer resin can be suitably used.

  Examples of the styrene-based thermoplastic elastomer resin include styrene-isoprene-styrene-based thermoplastic elastomer resin (SIS-based thermoplastic elastomer resin), styrene-butadiene-styrene-based thermoplastic elastomer resin (SBS-based thermoplastic elastomer resin), Examples thereof include styrene-ethylene-butene-styrene thermoplastic elastomer resin (SEBS thermoplastic elastomer resin), styrene-ethylene-propylene-styrene thermoplastic elastomer resin (SEPS thermoplastic elastomer resin), and the like. As the styrene-based thermoplastic elastomer resin, SIS-based thermoplastic elastomer resin is particularly suitable.

  In the present invention, as the thermoplastic elastomer resin, for example, a series of trade name “SIS” manufactured by JSR [for example, trade name “SIS 5405” (SIS thermoplastic elastomer resin; content ratio of styrene component: 18 mol%) , Trade name “SIS5002” (SIS thermoplastic elastomer resin; content ratio of styrene component: 22 mol%) and the like, and a series of product names “Septon” manufactured by Kuraray [for example, trade name “Septon 2104” (SIS System thermoplastic elastomer resin; content ratio of styrene component: 65 mol%, etc.] can be suitably used. In addition, the content ratio of the styrene component in the SIS thermoplastic elastomer resin means the ratio (mol%) of the repeating unit by the styrene component with respect to all the repeating units in the SIS thermoplastic elastomer resin.

  In the thermoplastic elastomer resin composition for forming the thermoplastic elastomer resin layer, a known additive (for example, a filler, a flame retardant, an anti-aging agent, an antistatic agent, a crosslinking agent, etc.) is optionally added. May be blended.

  The thermoplastic elastomer resin layer is formed by applying a thermoplastic elastomer resin composition containing a thermoplastic elastomer resin and, if necessary, various additives on a predetermined surface, and drying and curing as necessary. Can be formed.

In addition, when the thermoplastic elastomer resin or the composition thereof is applied to form the thermoplastic elastomer resin layer, the coating amount (solid content or dry weight) of the thermoplastic elastomer resin or the composition thereof is particularly limited. not, for example, 1 to 25 g / m ² (preferably 5 to 20 g / m ²⁾ can be selected from a range of.

  Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyamide-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, Fluorine-based adhesives, epoxy-based adhesives and the like can be mentioned. Among these, an acrylic pressure-sensitive adhesive is suitably used from the viewpoint of preventing contamination of the adherend. In addition, you may use an adhesive individually or in combination of 2 or more types.

  The pressure-sensitive adhesive layer can be formed by using a known or conventional forming method. For example, a method of applying a pressure-sensitive adhesive on a predetermined site or surface (application method), a release film such as a release liner, Examples thereof include a method (transfer method) of applying a pressure-sensitive adhesive to form a pressure-sensitive adhesive layer and then transferring the pressure-sensitive adhesive layer onto a predetermined site or surface. In forming the pressure-sensitive adhesive layer, a known or conventional coating method (such as a casting method, a roll coater method, a reverse coater method, a doctor blade method) can be used as appropriate.

  The sealing material which has an adhesive layer as a water-stopping layer can be used also as an adhesive sealing material, an adhesive tape or sheet, and an adhesive member.

(Seal material)
The sealing material of the present invention can be produced by subjecting the sheet-like resin foam obtained by the production method to at least a melt water stop treatment. Note that the sheet-like resin foam obtained by the above-described production method is a sheet-like resin foam having skin layers on the upper surface and the lower surface because air escapes from the thermoplastic polymer during production. Such a skin layer can be removed by slicing using a blade (for example, a splitting cutter, a hand saw, etc.). Accordingly, if a sheet-like resin foam having a skin layer on the upper surface and the lower surface is subjected to a slicing process to remove the skin layer, the cell structure is exposed, and the sheet resin is composed only of the cell structure (foam structure). A foam can be obtained.

  In the sealing material of the present invention, the upper surface and the lower surface are not subjected to a melt water stop treatment. Therefore, in the sealing material of the present invention, the cell structure may be exposed, but a water-stopping layer is usually provided on the upper surface and the lower surface. This is because, since the cell structure is a continuous structure or a semi-continuous semi-independent structure, if the cell structure is exposed, the water stoppage is adversely affected.

  In addition, when the melt water stop process is performed on the upper surface and the lower surface of the sealing material of the present invention, the heat is transmitted to the inside and the resin is melted, the bubble structure is lost, and the function as the sealing material may be lost. In particular, this is likely to occur with a thin sealing material.

  A sealing material having a cell structure of an open cell structure or a semi-continuous semi-closed cell structure and having a melt-stop treatment applied to the entire side surface is obtained, for example, by a sheet having a skin layer on an upper surface and a lower surface. It can be produced by subjecting the shaped resin foam to a slicing process for removing the skin layer, and then subjecting the entire side surface to a melt water stop treatment.

  A cell structure having an open cell structure or a semi-continuous semi-closed cell structure, a sealing material having skin layers on the upper surface and the lower surface and subjected to a melt and water stop treatment on the entire side surface is obtained by, for example, the above-described production method, It can be produced by subjecting the entire side surface of the sheet-like resin foam having a skin layer on the lower surface to a melt water-stopping treatment.

  A cell structure having an open cell structure or a semi-continuous semi-closed cell structure, a sealing material having a coating layer on the upper surface and the lower surface and subjected to a melt-stop treatment on the entire side surface is obtained by, for example, the above-described production method, The sheet-like resin foam having a skin layer on the lower surface is subjected to slicing processing to remove the skin layer to expose the cell structure, and then a coating layer is provided on the upper and lower surfaces where the cell structure is exposed, and then the entire side surface is provided. It can produce by performing a melt water stop process.

  The sealing material of the present invention preferably has a water absorption rate of less than 450 wt% (preferably less than 300 wt%, more preferably less than 100 wt%). This is because if the water absorption rate exceeds 450 wt%, the water-stopping property of the sealing material is lowered, making it difficult to use it in applications where water-stopping is required.

  The water absorption rate of the sealing material is defined as a percentage of “the total weight of distilled water absorbed by the sealing material after being immersed in distilled water for one day and the weight of the sealing material” with respect to “weight of the sealing material”. The

The sealing material of the present invention preferably has a 50% compression repulsion force of 5.5 N / cm ² or less (preferably 4.5 N / cm ² or less, more preferably 3.5 N / cm ² or less). When the 50% compression repulsion force exceeds 5.5 N / cm ² , the function as a sealing material is lowered due to a decrease in flexibility and may not be used for minute clearance.

  The shape, thickness, and the like of the sealing material of the present invention are not particularly limited and can be appropriately selected depending on the application. For example, the optimum thickness of the sealing material for a fine clearance of 0.10 to 0.20 mm is 0.2 to 1.0 mm, preferably 0.3 to 0.8 mm, more preferably 0.3 to 0.4 mm. It can be selected from a range of degrees.

  Since the sealing material of the present invention has the above-described characteristics, the bubbles are very fine, the flexibility is good, and the apparent density is low. That is, it has excellent flexibility that can handle minute clearances while keeping the cell diameter (bubble diameter) small. For this reason, it is possible to satisfactorily follow a further minute clearance while exhibiting water stopping performance. Moreover, it is highly foamed and lightweight.

  In addition, since the sheet-like resin foam is made of a thermoplastic polymer such as a thermoplastic elastomer, it has excellent flexibility. When an inert gas such as carbon dioxide is used as a foaming agent, the conventional physical foaming method and chemical foaming method can be used. In contrast, it is clean without generating harmful substances or leaving pollutants. Therefore, it can be suitably used particularly as a sealing material used inside an electronic device or the like.

  Therefore, the sealing material of the present invention is useful as a sealing material used when various members or parts (for example, optical members) are attached (attached) to a predetermined site. In particular, even when a small member or component (for example, a small optical member) is mounted on a thin product, it can be suitably used.

  As an optical member that can be attached (attached) using a sealing material, for example, an image display member (particularly, a small image display member) attached to an image display device such as a liquid crystal display, an electroluminescence display, or a plasma display, Examples thereof include a camera and a lens (particularly, a small camera and a lens) that are mounted on a mobile communication device such as a so-called “mobile phone” or “mobile information terminal”.

(Structure having optical member)
According to the sealing material of the present invention, it is possible to obtain a structure in which the optical member is attached (attached) to a predetermined site via the sealing material. Examples of such a structure include an image display device such as a liquid crystal display, an electroluminescence display, and a plasma display (in particular, an image display device in which a small image display member is mounted as an optical member), a camera, and a lens ( In particular, mobile communication devices such as so-called “mobile phones” and “portable information terminals” in which a small camera or lens) is mounted as an optical member. The structure may be a product that has been made thinner than before, and the thickness and shape thereof are not particularly limited.

(Water stop seal structure)
According to the sealing material of the present invention, it is possible to obtain a sealing structure in which an optical member is attached (attached) via the sealing material. As the water-stop seal structure, other structures are not particularly limited as long as the seal member is used when the optical member is attached (attached) to a predetermined site. Accordingly, the optical member and the predetermined part to which the optical member is attached are not particularly limited and can be appropriately selected. Examples of the optical member include the optical member as described above.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited at all by these Examples.

Example 1
Polypropylene [melt flow rate (MFR): 0.35 g / 10 min]: 45 parts by weight, polyolefin-based elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 45 parts by weight, polyethylene: 10 Parts by weight, magnesium hydroxide: 10 parts by weight, carbon (trade name “Asahi # 35” manufactured by Asahi Carbon Co., Ltd.): 10 parts by weight in a twin-screw kneader manufactured by Japan Steel Works (JSW) at 200 ° C. After kneading at the temperature, it was extruded into a strand, cooled to water, and formed into a pellet. The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected under an atmosphere of 220 ° C. at a pressure of 13 (12 after injection) MPa. Carbon dioxide gas was injected at a ratio of 5% by weight with respect to the total amount of the polymer. After sufficiently saturating the carbon dioxide gas, cooling to a temperature suitable for foaming, and extruding from a die, a sheet-like foam having a semi-continuous semi-closed cell structure [referred to as “sheet-like foam (A)”] is obtained. It was.
A skin layer is formed on the upper surface and the lower surface of the sheet-like foam (A). In the foam, the apparent density is 0.05 g / cm ³ and the thickness of the cell structure layer (foam layer). The thickness of the skin layer on the upper surface and the lower surface was 0.02 mm. Further, the open cell ratio in the center of the foam excluding the skin layer was 80%.
The sheet-like foam (A) is cut by irradiating a laser beam vertically from the upper or lower surface under the conditions shown in Table 1 below, thereby having skin layers on the upper and lower surfaces and melting the entire side surface. A foam was obtained.

(Example 2)
After obtaining a sheet-like foam (A) in the same manner as in Example 1, the upper and lower skin layers of the sheet-like foam (A) were removed with a splitting cutter, and the upper and lower skin layers were removed. A sheet-like foam was obtained.
Toluene solvent is added to a thermoplastic elastomer resin (trade name “SIS5405” manufactured by JSR; styrene-isoprene-styrene thermoplastic elastomer resin; styrene component content ratio: 18 mol%), and the solid content concentration is 20% by weight. It was diluted with a Mayer bar and applied to the upper and lower surfaces of the sheet-like foam from which the skin layer had been removed at a coating weight of 15 g / m ^{2 in} terms of dry weight (solid weight), and then heated at 80 ° C. for 3 minutes. It dried and formed the thermoplastic elastomer resin layer (coat layer, SIS layer).
A sheet-like foam having a coating layer on the upper surface and the lower surface is cut from the upper surface or the lower surface by irradiating a laser under the conditions shown in Table 1 above, so that the upper surface and the lower surface have coating layers and the entire side surface is melted. A treated foam was obtained.
In the foam, the apparent density was 0.05 g / cm ³ , the thickness of the cell structure layer (foam layer) was 0.5 mm, and the thicknesses of the coat layers on the upper surface and the lower surface were both 0.02 mm. .

(Comparative Example 1)
After obtaining a sheet-like foam (A) in the same manner as in Example 1, the upper and lower skin layers of the sheet-like foam (A) are removed with a splitting cutter and cut into a predetermined shape with a Thomson blade. Thus, a foam was obtained.
The foam did not have a resin melted part on the side surface.

(Comparative Example 2)
After obtaining a sheet-like foam (A) in the same manner as in Example 1, it was cut into a predetermined shape with a Thomson blade to obtain a foam.
The foam had skin layers on the upper and lower surfaces, but did not have a resin melted part on the side.

(Comparative Example 3)
As the foam, a sheet-like foam [trade name “Epsitoler” manufactured by Nitto Denko Corporation, sealing material (sealing material), closed cell structure] mainly composed of ethylene-propylene-diene rubber (EPDM) was used.

(Evaluation)
About the foams of the examples and comparative examples, the water stoppage is evaluated by measuring the “water absorption rate”, and the flexibility is further measured by measuring the “repulsive force at 50% compression (50% compression repulsive force)”. evaluated.

Evaluation of waterstop The water absorption was measured by the following (Method of measuring water absorption) and evaluated according to the following criteria.
Very good (◎): water absorption of less than 100 wt% when immersed for 1 day Good (○): water absorption of less than 450 wt% after immersion for 1 day Poor (X): water absorption of immersed for 1 day 450wt% or more

(Measurement method of water absorption)
The foam was aged in an atmosphere of 23 ° C. for 30 minutes, and then the weight of the foam was measured and taken as “weight of foam before immersion”.
Next, the foam was immersed in distilled water adjusted to 70 ° C. for 1 day (24 hours). After the immersion, the weight of the foam was measured and defined as “weight of the foam after immersion”.
And the weight change (water absorption rate) of the foam represented by the change in weight after being immersed in water for 1 day (24 hours) relative to the weight before being immersed in water was determined from the following formula.
Water absorption (%) = (weight of foam after immersion−weight of foam before immersion) / (weight of foam before immersion) × 100

Evaluation of flexibility The 50% compression repulsion rate was measured by the following method (measurement method of 50% compression repulsion rate) and evaluated according to the following criteria.
Good (◯): 50% compression repulsion rate is less than 5.5 N / cm ² Poor (x): 50% compression repulsion rate is 5.5 N / cm ² or more

(Measurement method of 50% compression repulsion rate)
The 50% compression repulsion force (50% compression repulsion force) was measured based on JIS K 6767. Specifically, the foam was compressed at a compression rate of 2.54 mm / min until the volume reached 50%, and the stress at that time was determined by converting (N) per unit area (cm ² ).

  Moreover, the cross section of the Example was observed with the scanning electron microscope (SEM). In addition, Hitachi High-Technologies Corporation S-3400N was used as a scanning electron microscope (SEM). The scanning electron micrograph (SEM image) of the cross section of each Example was shown in FIGS. The magnification of the scanning electron micrograph is 200 times.

1 is an electron micrograph of the cross section of Example 1. FIG. FIG. 2 is an electron micrograph of the cross section of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting water stopping part 2 Skin layer 3 Coat layer

Claims (10)

  It is a sealing material composed of a sheet-like resin foam having an open cell structure or a semi-continuous semi-independent structure, and the upper surface and the lower surface are not melt-stopped, and the entire side surface is melt-stopped. Sealing material characterized by   The sealing material according to claim 1, wherein the melt water stopping treatment is a resin solidification treatment using laser irradiation.  Furthermore, the sealing material of Claim 1 or 2 which has a water stop layer in at least one surface among an upper surface and a lower surface.   The sealing material according to claim 3, wherein the sealing layer has a skin layer.   The sealing material according to claim 3, which has a coat layer as the water blocking layer.   The sealing material according to claim 5, wherein the coat layer is a resin layer.   The sealing material of Claim 3 which has an adhesive layer as a water stop layer.   The sealing material according to any one of claims 1 to 7, wherein the water absorption is less than 450 wt%. The sealing material according to any one of claims 1 to 8, wherein the 50% compression repulsion force is 5.5 N / cm ² or less.   An adhesive sealing material having a configuration in which an adhesive layer is provided on at least one surface of the sealing material according to any one of claims 1 to 9.