JP4860207B2 - Method for producing low density polyurethane foam - Google Patents

Description

The present invention relates to the production how low-density polyurethane foam. This foam is particularly useful for manufacturing a seal member suitable for being disposed between the periphery of the liquid crystal display screen or the periphery of the microphone in the display part of a mobile communication device such as a mobile phone and the inner surface of the case. It is.

  In general, electric devices such as a display in a television, a computer, a mobile phone, or a portable information terminal are arranged such that an internal device such as a liquid crystal display, a microphone, or a speaker faces the outside of the housing. By using a seal member between the peripheral edge of the internal device and the housing, dustproofness is improved, and light leakage and impact damage from a backlight or the like are prevented.

  In many applications including small devices typified by recent mobile phones, an increase in function, advancement, and weight reduction are desired. Therefore, the required characteristics for the seal member have become more sophisticated. For example, the increase and sophistication of the functions in recent mobile phones have been achieved by increasing the degree of integration of components by unifying the size of ICs used, saving space by introducing large-scale LSIs (VLSI), and multilayering of substrates. Thus, when a large number of parts are integrated inside the casing of the mobile phone, the internal structure of the casing, for example, the fitting structure of the casing becomes more complicated. A gap is formed between the internal component and the housing, and the seal member needs to be disposed between the internal component and the housing. However, the sealing member needs to provide sufficient sealing performance for a wide range of compression ratios (from low to high) in accordance with changes in the size of the gap to be filled.

  Generally, the sealing performance of the seal member is determined by whether or not the seal member is easily deformed by a load. Therefore, in order for the sealing member to have sufficient sealing properties at the time of high compression, low density soft polyurethane foam, olefin foam such as polyethylene foam or polypropylene foam, rubber foam, or the like is used. However, after the foam is obtained in the slab state, it is often cut into sheets of the required thickness, resulting in a soft and thin foam. Such a foam does not have a skin layer and has poor adhesion. For this reason, such a foam does not have a desired degree of dustproofness and light-shielding properties. A foam having a skin layer can also be produced from the material, but the compression residual strain of such a sealing member is large, and it is difficult for the foam to maintain a stable sealing property for a long period of time. Furthermore, since the cell (bubble) diameter of such a foam is large, a problem arises in dustproof performance and light shielding performance.

  In addition, materials of high electrical conductivity, light weight, and high strength, such as magnesium alloys, are generally used for the casings of various electric appliances. In order to efficiently avoid problems such as generation of electromagnetic waves based on this material, a material having a low relative dielectric constant, that is, a material having high insulation is desired for the seal member. However, since the relative dielectric constant is a value inherent to the material, it is difficult to select a material having both a sealing property and a low relative dielectric constant.

  Patent Document 1 specifically discloses a polyurethane foam as a sealing member. This polyurethane foam is formed according to the mechanical floss method, and easily deforms with a low load at 25% compression. A plastic film as a backup material is integrally formed on one surface of the polyurethane foam. In the mechanical froth method, an organic isocyanate component, an active hydrogen-containing component, a surfactant, and a catalyst are mixed, and then the mixture is mechanically stirred to disperse the inert gas throughout the mixture, thereby forming a thermosetting foam composition. The polyurethane foam is formed by further forming the foamed composition and curing the foamed composition.

Polyurethane foams can also be formed by physically or chemically foaming the isocyanate component, active hydrogen-containing component mixture, and other additives, followed by subsequent curing. Each of these foam manufacturing methods has several disadvantages, particularly when thin polyurethane foam portions are required that are low density and uniform throughout the cross-section. For example, foams formed by mechanically foaming a polyurethane liquid phase using air or an inert gas often have a uniform cell structure with good physical properties. However, such foams are also not preferred because they are high density products exceeding about 240 kg / m ³ per cubic meter (about 15 pounds per cubic foot (pcf)). This foam is also very difficult to produce to a thickness of, for example, less than 13 mm (0.5 inch), preferably less than 5 mm (0.2 inch), especially less than 3 mm (0.12 inch). . On the other hand, foams produced by physical or chemical foaming can have a cell density as low as about 32 kg / m ³ (about 2 pcf), but the cell structure is also irregular. Therefore, the thin product produced by this method has poor physical properties.
JP 2001-100216 A

In view of these drawbacks, in the art, the thickness is less than 13 mm (0.5 inch), preferably less than 3 mm (0.12 inch), and the density is up to about 400 kg / m ³ (up to about 25 pcf). ), Preferably 50 to 250 kg / m ³ ( ^{3 to} 15.6 pcf) and a low hardness foam having a uniform cell structure.

In order to achieve the above object, the invention described in claim 1 is a method for producing a low-density polyurethane foam used for a sealing member, and according to a mechanical floss method, an isocyanate-containing component, the isocyanate-containing component, and A foaming composition is prepared by mixing and stirring a foaming gas in a reactive polyurethane-forming composition comprising a reactive hydrogen-containing component that reacts, a foaming agent containing water , a surfactant, and a catalyst system that delays curing of the foam. Adjusting the product , casting the foamed composition on the first support, and disposing a second support on the surface of the cast foam composition opposite to the first support. And after expanding and curing the foamed composition, the second support is peeled off from the surface , and the density is 50 to 250 kg / m ³ and the thickness is 0.5 to 13 mm. A polyu And a step of obtaining a foamed foam layer. A method for producing a low density polyurethane foam is provided.
The invention according to claim 2 is the method according to claim 1, wherein the polyurethane foam layer is a polyurethane foam layer in which 50% CLD is 0.025 MPa or less and 75% CLD is 0.40 MPa or less. I will provide a.

The invention according to claim 3, wherein the second support provides a method according to claim 1 for imparting a smooth surface finish to the polyurethane foam.
The invention according to claim 4 is provided with a release layer on at least one surface of the first support, and the foamed composition for forming reactive polyurethane is in contact with the release layer of the first support. 1 is provided.

The invention according to claim 5 provides the method according to claim 1, further comprising the step of passing the first support, the foamed composition and the second support through a thickness adjusting means.
The invention according to claim 6 provides the method according to claim 1, wherein the first support is bonded to a polyurethane foam layer cured in contact .

The invention according to claim 7, wherein the active hydrogen-containing component viewed contains a polyether polyol, ethylene oxide content of the polyether polyol, according to claim 1 is 20 wt% or less based on the weight of the polyol Provide a way .

The invention according to claim 8 provides the method according to claim 1, wherein the foaming agent comprises a chemical foaming agent .

The invention according to claim 9 provides the method according to claim 1, wherein the blowing agent comprises a physical blowing agent.
The invention according to claim 10 is characterized in that the physical blowing agent is 1,1-dichloro-1-fluoroethane, 1,1-dichloro-2,2,2-trifluoro-ethane, monochlorodifluoromethane, 1-chloro. -1,1-difluoroethane; 1,1,1,3,3,3-hexafluoropropane, 2,2,4,4-tetrafluorobutane, 1,1,1,3,3,3-hexafluoro- 2-methylpropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1 , 2,3,3-pentafluoropropane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3,4-hexafluorobutane, 1,1,1,3,3 -Pentafluorobutane, 1,1,1, , 4,4-hexafluorobutane, 1,1,1,4,4-pentafluorobutane, 1,1,2,2,3,3-hexafluoropropane, 1,1,1,2,3,3 -Hexafluoropropane, 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, methyl-1,1,1-trifluoroethyl ether, difluoromethyl-1,1,1-tri The method according to claim 9 , which is fluoroethyl ether; n-pentane, isopentane, cyclopentane, or a combination containing at least one of the above blowing agents.

The invention according to claim 11 provides the method according to claim 1, wherein the catalyst comprises metal acetylacetonate.
Invention of Claim 12 provides the method of Claim 1 in which the said polyurethane foam layer contains the cell whose average cell diameter is 20-500 micrometers.

The invention according to claim 13 provides the method according to claim 1, wherein the polyurethane foam layer has a relative dielectric constant of 1 to 2.0 at each frequency of 10 kHz, 100 kHz, and 1 MHz.

  Next, a polyurethane foam layer suitable for use as a sealing member, for example, and a method for producing the same according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. The inventors of the present application have found that when the polyurethane layer is produced by the mechanical floss method, the density of the sealing member is reduced by increasing the amount of foaming gas forming the cell. Such a foam can be highly compressed with a low load, and even a slight gap, for example, a slight gap in a housing fitting portion in a device such as a mobile phone, can ensure sufficient sealing performance.

  Regarding the reactive mixture prepared using the mechanical floss method, the following two points were experimentally confirmed. First, it was observed that as the foaming gas was increased, the apparent viscosity of the polyurethane foam raw material increased. In other words, as shown in FIG. 1, when the foaming density of the liquid foam composition (foamed polyurethane foam raw material) is lower, the foam viscosity of the liquid foam composition (polyurethane foam before curing) The viscosity of the raw material) increases exponentially. This presents several difficulties in casting and curing the foam composition. For example, when the thickness of the cast foamed composition is controlled by contact with a roll or the like, the foamed composition does not easily peel from the roll, thereby roughening the surface of the foamed composition in contact with the roll. . Second, when producing a low density foamed polyurethane sheet, it was observed that the thinner the foamed polyurethane sheet, the rougher the surface of the sheet.

  Therefore, in order to avoid this phenomenon, a material sheet having a smooth surface is used to control the thickness of the polyurethane foam raw material, thereby making it possible to obtain a foam having a good surface shape. .

  Alternatively, or in addition, it has also been found that very thin and low density polyurethane foams can be easily produced by using a two-stage foaming / expansion method. This method comprises the steps of mechanically foaming a polyurethane liquid phase containing a suitable blowing agent, casting the liquid foam composition on a first (lower) support, followed by casting. Expanding and curing the foamed composition under a second (upper) support. The catalyst system is selected such that the curing of the foam composition can be delayed so that expansion is substantially complete before curing occurs. This foam was found to have a uniform cell structure. The foam can also have improved mechanical properties.

  The polyurethane foams described herein can be used in several commercial applications such as sealing applications and mobile phone gaskets. As shown in FIG. 2, the sealing member 10 is basically composed of, for example, a foamed polyurethane layer 12 and a base film 14, and the foamed polyurethane layer 12 provides necessary cushioning properties, flexibility, and sealing properties, The base film 14 is bonded to one surface of the foamed polyurethane layer 12 to increase the structural strength of the seal member 10. This polyurethane foam layer 12 is manufactured according to the following mechanical floss method.

In general, polyurethane foam is formed from a reactive composition comprising an organic isocyanate component that reacts with an active hydrogen-containing component, a surfactant (foam stabilizer) and a catalyst. The organic isocyanate component used in the preparation of the polyurethane foam is usually of the general formula: Q (NCO) _i (where i is an integer having an average value greater than 2 and Q is an organic group having a valence of i) The polyisocyanate represented by this is included. Q may be a substituted or unsubstituted hydrocarbon group (that is, an alkane or an aromatic group having an appropriate valence). Q is a group represented by the general formula Q ¹ -ZQ ¹ (wherein Q ¹ is an alkylene or arylene group, Z is —O—, —O—Q ¹ —S—, —CO—, —S—, — S—Q ¹ —S, —SO— or —SO ₂ —). Examples of suitable isocyanates include hexamethylene diisocyanate, 1,8-diisocyanate-p-methane, xylyl diisocyanate, diisocyanate cyclohexane, phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and crude triisocyanate. Tolylene diisocyanate including diisocyanate, bis (4-isocyanatophenyl) methane, chlorophenylene diisocyanate, diphenylmethane-4,4′-diisocyanate (also called 4,4′-diphenylmethane diisocyanate or MDI) and its adduct, naphthalene-1 , 5-diisocyanate, triphenylmethane-4,4 ′, 4 ″ -triisocyanate, isopropylbenzene-α-4-diisocyanate, and poly And polymer isocyanates such polyphenyl isocyanate.

Q may also be a polyurethane group with a valence of i, where Q (NCO) _i is a composition commonly known as a prepolymer. Such a prepolymer is obtained by reacting a stoichiometric excess of the above and below described polyisocyanates with an active hydrogen containing component as described below, in particular a polyhydroxyl containing material, or a polyol as described below. Formed by. Usually, the polyisocyanate is used in a stoichiometric excess of, for example, about 30% to 200%, and this stoichiometry is based on the equivalent amount of isocyanate groups per equivalent of hydroxyl groups in the polyol. The amount of polyisocyanate used varies slightly depending on the nature of the polyurethane being prepared.

  The active hydrogen-containing component may include polyether polyols and polyester polyols. Suitable polyester polyols include polycondensation products of polyols with dicarboxylic acids or ester-forming derivatives thereof (eg anhydrides, esters, halides), lactones in the presence of polyols. Polylactone polyols obtained by ring-opening polymerization, polycarbonate carbonates obtained by reaction of carbonic acid diesters with polyols, and castor oil polyols are included. Dicarboxylic acids that are useful and suitable for the production of polycondensed polyester polyols and derivatives thereof include aliphatic dicarboxylic acids such as glutaric acid, adipic acid, sebacic acid, fumaric acid, maleic acid or alicyclic dicarboxylic acids; dimer acids Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; tribasic or higher functional polycarboxylic acids such as pyromellitic acid; and anhydrides such as maleic anhydride, phthalic anhydride and dimethyl terephthalate; Secondary alkyl esters are mentioned.

  A further active hydrogen-containing component is a polymer of cyclic esters. Preparation of cyclic ester polymers from at least one cyclic ester monomer is described in US Pat. Nos. 3,021,309 to 3,021,317; 3,169,945; and This is well documented in the patent literature as exemplified in US Pat. No. 2,962,524. Suitable cyclic ester monomers include δ-valerolactone; ε-caprolactone; ζ-enanthlactone; monoalkyl-valerolactone, such as monomethyl-valerolactone, monoethyl-valerolactone, and monohexyl-valerolactone. It is not limited to. Generally, the polyester polyol may include a mixture containing any one of caprolactone-based polyester polyols, aromatic polyester polyols, ethylene glycol adipate-based polyols, and the above-described polyester polyols. Polyester polyols produced from ε-caprolactone, adipic acid, phthalic anhydride, terephthalic acid or dimethyl terephthalate are generally preferred.

  Polyether polyols include alkylene oxides such as ethylene oxide, propylene oxide and mixtures thereof, water or ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butylene glycol, 1,3-butanediol, 1,4-butane. Diol, 1,5-pentanediol, 1,2-hexylene glycol, 1,10-decanediol, 1,2-cyclohexanediol, 2-butene-1,4-diol, 3-cyclohexene-1,1-di Methanol, 4-methyl-3-cyclohexene-1,1-dimethanol, 3-methylene-1,5-pentanediol, diethylene glycol, (2-hydroxyethoxy) -1-propanol, 4- (2-hydroxyethoxy)- 1-butanol, 5- (2-hydroxy Propoxy) -1-pentanol, 1- (2-hydroxymethoxy) -2-hexanol, 1- (2-hydroxypropoxy) -2-octanol, 3-allyloxy-1,5-pentanediol, 2-allyloxymethyl 2-methyl-1,3-propanediol, [4,4-pentyloxy) -methyl] -1,3-propanediol, 3- (o-propenylphenoxy) -1,2-propanediol, 2,2 '-Diisopropylidenebis (p-phenyleneoxy) diethanol, glycerol, 1,2,6-hexanetriol, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, 3- (2- Hydroxyethoxy) -1,2-propanediol, 3- (2-hydroxypropoxy) -1,2-propanedioe 2,4-dimethyl-2- (2-hydroxyethoxy) -methylpentanediol-1,5; 1,1,1-tris [2-hydroxyethoxy) methyl] -ethane, 1,1,1-tris [ 2-hydroxypropoxy) -methyl] propane, diethylene glycol, dipropylene glycol, pentaerythritol, sorbitol, sucrose, lactose, α-methyl glucoside, α-hydroxyalkyl glucoside, novolac resin, phosphoric acid, benzene phosphoric acid, tripolyphosphoric acid and tetra It can be obtained by chemically adding to polyphosphoric acids such as polyphosphoric acid and polyvalent organic components such as ternary condensation products. The alkylene oxides used in producing the polyoxyalkylene polyols usually have 2 to 4 carbon atoms. Propylene oxide and a mixture of propylene oxide and ethylene oxide are preferred. The polyols can themselves be used as active hydrogen components.

Preferred types of polyether polyols are usually of the general formula: R [(OCH _n H _2n ) _Z OH] _a , where R is hydrogen or a polyvalent hydrocarbon group and a is an integer equal to the valence of R (Ie, 1 or 2 to 6 to 8), n is an integer of 2 to 4 (preferably 3), and z is an integer of 2 to 200, preferably 15 to 100). Preferred polyether polyols comprise a mixture of one or several dipropylene glycols, 1,4-butanediol and 2-methyl-1,3-propanediol.

  Another type of active hydrogen-containing component that can be utilized is a polymer polyol composition obtained by polymerizing ethylenically unsaturated monomers in a polyol as described in US Pat. No. 3,383,351. It is a thing. Monomers suitable for the production of such compositions include acrylonitrile, vinyl chloride, styrene, butadiene, vinylidene chloride, and other ethylenically unsaturated monomers identified and described in the above US patents. Suitable polyols include those described above and in US Pat. No. 3,383,351. The polymer polyol composition may contain 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more of the monomer polymerized in the polyol, based on the total amount of polyol. The polymer polyol composition preferably contains not more than 70% by weight of monomer polymerized in the polyol, preferably not more than 50% by weight, more preferably not more than 40% by weight. Such compositions are advantageously used in selected polyols in the presence of radical polymerization catalysts such as peroxides, persulfates, percarbonates, perborates, azo compounds, etc. It is adjusted by polymerizing the monomers at a temperature of 150 ° C.

  Active hydrogen-containing components are also hydroxyl-terminated polyhydrocarbons (US Pat. No. 2,877,212); hydroxyl-terminated polyformals (US Pat. No. 2,870,097); fatty acid triglycerides ( U.S. Pat. Nos. 2,833,730 and 2,878,601); hydroxyl-terminated polyesters (U.S. Pat. Nos. 2,698,838, 2,921,915); 2,591,884 specification, 2,866,762 specification, 2,850,476 specification, 2,602,783 specification, 2,729,618 specification, 2,779,689, 2,811,493, 2,621,166 and 3,169,945); hydroxymethyl-terminated parf Oromethylenes (US Pat. Nos. 2,911,390 and 2,902,473); Hydroxyl-terminated polyalkylene ether glycols (US Pat. No. 2,808,391; British Patent 733) , 624); hydroxyl-terminated polyalkylene arylene ether glycols (US Pat. No. 2,808,391); and hydroxyl-terminated polyalkylene ether triols (US Pat. No. 2,866,774). Polyhydroxyl-containing compounds such as

  The polyols can have a wide range of hydroxyl numbers. In general, the hydroxyl number of polyols is 28 to 1000 or more, preferably 100 to 800, including other crosslinking additives when used. This hydroxyl number is completely neutralized with hydrolysis products of fully acetylated derivatives prepared from a mixture of polyols containing 1 g polyol, or other crosslinkable additives or no other crosslinkable additives. Defined as the number of milligrams of potassium hydroxide required to sum. This hydroxyl number can also be defined by the following formula:

式中、ＯＨはポリオールのヒドロキシル価であり、ｆはポリオール１分子当たりの平均ヒドロキシル基数である平均官能基数であり、Ｍ．Ｗ．はポリオールの平均分子量である。

Where OH is the hydroxyl number of the polyol, f is the average number of functional groups, which is the average number of hydroxyl groups per molecule of polyol; W. Is the average molecular weight of the polyol.

  When a wide variety of blowing agents or mixtures thereof are used, including at least one of chemical blowing agents and physical blowing agents, they can be used in the reactive composition. Examples of the chemical foaming agent include water and a compound that decomposes with a high gas generation amount under a specific condition, for example, within a narrow temperature range. The degradation products formed during the degradation process are preferably physiologically safe and do not substantially adversely affect the thermal stability or mechanical properties of the polyurethane foam sheet. Furthermore, it is preferred that the decomposition products do not disentangle or that the decomposition products do not have a discoloring effect on the foam product.

  Suitable chemical blowing agents include water. When water is used as the blowing agent, it is generally preferred to control the curing reaction by selectively using a catalyst. Water is usually used as a blowing agent in an amount of 0.1 to 8% by weight of the total amount of the reactive composition. Azo compounds such as azoisobutyronitrile, azodicarbonamide (ie azobisformamide) and barium azodicarboxylate; substituted hydrazines such as diphenylsulfone-3,3′-disulfohydrazide, 4,4′-hydroxy -Bis- (benzenesulfohydrazide), trihydrazinotriazine or aryl-bis- (sulfohydrazide); semicarbazides such as p-tolylenesulfonyl semicarbazide or 4,4'-hydroxy-bis- (benzenesulfonyl semicarbazide); triazole For example 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso compounds such as N, N′-dinitrosopentamethylenetetramine or N, N-dimethyl-N, N′-dinitrosophthal Amido; Benzo Spoon, such isatoic acid; or for example other chemical blowing agent in the mixture such as sodium carbonate / citric acid mixtures may be used. The amount of blowing agent will vary depending on the drug and the desired foam density and can be readily determined by one skilled in the art. Usually these blowing agents are used in an amount of 0.1 to 10% by weight of the total amount of the reactive composition.

  Physical blowing agents may be used alone or as a mixture with physical blowing agents or with one or several chemical blowing agents. The physical blowing agent can be selected from a wide range of materials including hydrocarbons, ethers, esters, and partially halogenated hydrocarbons, ethers, esters, and the like. The boiling point of typical physical blowing agents is -50 ° C to 100 ° C, preferably -50 ° C to 50 ° C. Typical physical blowing agents include 1,1-dichloro-1-fluoroethane, 1,1-dichloro-2,2,2-trifluoro-ethane, monochlorodifluoromethane, and 1-chloro-1,1- CFCs (chlorofluorocarbons) such as difluoroethane; 1,1,1,3,3,3-hexafluoropropane, 2,2,4,4-tetrafluorobutane, 1,1,1,3,3,3 -Hexafluoro-2-methylpropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane 1,1,2,3,3-pentafluoropropane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3,4-hexafluorobutane, 1,1,1 , 3,3-penta Luobutane, 1,1,1,4,4,4-hexafluorobutane, 1,1,1,4,4-pentafluorobutane, 1,1,2,2,3,3-hexafluoropropane, 1, FCs (fluorocarbons) such as 1,1,2,3,3-hexafluoropropane, 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, and pentafluoroethane; methyl-1,1 , 1-trifluoroethyl ether and difluoromethyl-1,1,1-trifluoroethyl ether and other FEs (fluoroethers); and n-pentane, isopentane, and cyclopentane hydrocarbon water. Similar to chemical blowing agents, physical blowing agents are used in an amount sufficient to give the resulting foam the desired bulk density. Usually, the physical blowing agent is used in an amount of 5-50% by weight of the reactive composition, usually 10-30% by weight of the reactive composition. In one embodiment, water is used as the blowing agent with one or more physical blowing agents.

  Many catalysts commonly used to catalyze the reaction of an isocyanate component and an active hydrogen-containing component can be used in the preparation of the foam. Such catalysts include bismuth, lead, tin, iron, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese and zirconium organic acid salts, inorganic Examples include acid salts and organometallic derivatives, as well as phosphines and tertiary organic amines. Examples of such catalysts include dibutyltin dilaurate, dibutyltin diacetate, tin 2-ethylhexanoate, lead 2-ethylhexanoate, cobalt naphthenate, triethylamine, triethylenediamine, N, N, N ′, N′— Tetramethylethylenediamine, 1,1,3,3-tetramethylguanidine, N, N, N ′, N′-tetramethyl-1,3-butanediamine, N, N-dimethylethanolamine, N, N-diethylethanol Amines, 1,3,5-tris (N, N-dimethylaminopropyl) -s-hexahydrotriazine, o- and p- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol N, N-dimethylcyclohexylamine, pentamethyldiethylenetriamine, 1,4-di Zobicyclo [2.2.2] octane, N-hydroxyl-alkyl quaternary ammonium carboxylates, tetramethylammonium formate, tetramethylammonium acetate, tetramethylammonium 2-ethylhexanoate, and any one of the above catalysts A composition containing a seed may be mentioned.

  Aluminum, barium, cadmium, calcium, cerium (III), chromium (III), cobalt (II), cobalt (III), copper (II), indium, iron (II), lanthanum, lead (II), manganese (II ), Manganese (III), neodymium, nickel (II), palladium (II), potassium, samarium, sodium, terbium, titanium, vanadium, yttrium, zinc, zirconium, and other metal acetylacetonates are preferred. Common catalysts are bis (2,4-pentanedionate) nickel (II) (nickel acetyl, such as nickel diacetonitrile diacetylacetonate nickel, diphenylnitrile diacetylacetonate nickel, bis (triphenylphosphine) diacetylacetylacetonate nickel. Acetonate or diacetylacetonate nickel) and derivatives thereof. Iron acetylacetonate (FeAA) is particularly preferred due to its stability, good catalytic activity and non-toxicity.

  Acetylacetone (2,4-pentanedione) is added to the metal acetylacetonate as disclosed in Simpson US Pat. No. 5,733,945. Acetylacetone provides a thermal incubation period, thereby providing the necessary mixing, casting and other procedure times, and avoiding premature premature curing during low temperature processing. However, the material is cured in several heating zones and acetylacetone is driven off as the temperature of the urethane mixture increases. When acetylacetone is removed and concomitantly loses its retarding function, the metal acetylacetonate can regain its normal high reactivity and provide a very high level of catalysis at the end of the polyurethane reaction. This high reactivity late in the process cycle is advantageous and results in improved physical properties such as compression set. In general, the ratio of metal acetylacetonate to acetylacetone is 2: 1 on a weight basis.

The amount of catalyst present in the reactive composition is preferably 0.03% to 3.0% by weight based on the weight of the active hydrogen-containing component.
In one embodiment, FeAA is selected as the catalyst when water is used as the blowing agent. Other catalysts or auxiliaries such as amines can be used to adjust the relative reaction rate of water and urethane. Water emits CO ₂ reacts with the isocyanate. FeAA with acetylacetone at the same time catalyzes the curing reaction in a delayed manner to prevent premature curing, thus allowing chemical (and optionally physical) foaming to proceed unhindered. This catalyst ultimately allows complete curing of the polyurethane foam. The metal acetylacetonate is most conveniently added pre-dissolved in a suitable solvent such as dipropylene glycol or other hydroxyl-containing component and then added to the reaction to become part of the final product.

A wide variety of surfactants, including mixtures of surfactants, can be used to stabilize the polyurethane foam prior to its curing. Organosilicone surfactants are particularly useful. Preferred organosilicone surfactants are copolymers composed essentially of SiO ₂ (silicate) units and (CH ₃ ) ₃ SiO _0.5 (trimethylsiloxy) units, where silicate units and trimethylsiloxy units are Is a molar ratio of 0.8: 1 to 2.2: 1, preferably 1: 1 to 2.0: 1. Other preferred organosilicone surfactants are partially cross-linked siloxane-polyoxyalkylene block copolymers and mixtures thereof, wherein the siloxane block and polyoxyalkylene block are bonded to carbon via silicon, or bonded to silicon. To the oxygen-carbon bond. The siloxane block is composed of hydrocarbon-siloxane groups, and has an average of at least divalent silicon for each block bonded by the bond. At least a part of the polyoxyalkylene block is composed of an oxyalkylene group and is polyvalent. That is, at least a part of the polyoxyalkylene block has at least one of divalent carbon and oxygen bonded to carbon for each block bonded by the bond. The remaining polyoxyalkylene block consists of oxyalkylene groups and is monovalent. That is, the remaining polyoxyalkylene block has at least one of monovalent carbon and oxygen bonded to carbon for each block bonded by the bond. Further, U.S. Pat. Nos. 2,834,748, 2,846,458, 2,868,824, 2,917,480, and 3,057, Conventional organopolysiloxane-polyoxyalkylene block copolymers such as those described in the '901 specification can be used. The amount of organosilicone polymer used as the foam stabilizer can vary over a wide range, for example from 0.5% to 10% by weight or more based on the amount of active hydrogen component. Preferably, the amount of organosilicone copolymer present in the foam formulation varies from 1.0 wt% to 6.0 wt% on the same basis.

  In addition, optional additives may be added to the polyurethane foam mixture during the manufacturing process. For example, fillers (alumina trihydrate, silica, talc, calcium carbonate, clay, etc.), dyes, pigments (eg titanium dioxide and iron oxide), antioxidants, ozone degradation inhibitors, flame retardants, UV stabilizers, Commonly used additives such as conductive fillers and conductive polymers can be used.

In one embodiment, the reactive composition for producing a foam according to the present invention basically conforms to the contents disclosed in Japanese Patent Publication No. 53-8735. However, certain polyol compositions are preferred in order to provide each of the densities and relative dielectric constants in the ranges described herein. Desirable polyols for use are repeating units ("units") such as at least one of PO (propylene oxide) and PTMG (tetrahydrofuran ring-opening polymerized) except for EO (ethylene oxide; (CH ₂ CH ₂ O) _n ). Have). This is because if a polyol containing a large amount of EO units is used, the resulting foam exhibits hygroscopicity and the relative permittivity of the foam increases. Specifically, the predetermined dielectric constant described in the present application can be achieved by setting the ratio of EO units (or EO unit ratio) in the polyol to 20% or less. For example, when the polyol used consists only of PO units and EO units, this polyol is set to be in the range of [PO units]: [EO units] = 100: 0 to 80:20. In the present invention, the ratio of EO units is referred to as “EO content”.

  Foam is obtained by mechanically mixing a reactive composition (ie, isocyanate component, active hydrogen-containing component, foam stabilizing surfactant, catalyst and other optional additives) with a predetermined amount of foaming gas. Can be manufactured. As shown in FIG. 4, the foaming mixture (polyurethane foam raw material) is continuously supplied onto a base film 14 that is also used as a moving means in the manufacturing process. In the present application, the base film 14 is also referred to as a first support or a lower support layer. Furthermore, on the upper side of the foaming mixture, a surface protective film 16 which is also referred to as a second support or an upper support in the present application is provided. Therefore, the foaming reactive composition is sandwiched between the two upper and lower films 14 and 16 and formed into a sheet that is protected so that the surface is not roughened and has a controlled thickness. Thereby, the polyurethane foam sheet 12 is manufactured. This mechanical flossing method and individual raw materials therefor are disclosed in detail, for example, in Japanese Patent Publication No. 53-8735. Methods suitable for mechanical floss are also described in more detail below.

  In other embodiments, the foam may be manufactured by a combination of mechanical floss and expansion (chemical foaming or physical foaming). In one method of this approach, the components for producing the low density foam, ie, isocyanate component, active hydrogen-containing component, catalyst, chemical blowing agent and other desirable additives are first mixed together and then mechanical flossing by air. Is given. Alternatively, these components may be dropped sequentially into the liquid phase during the mechanical flossing process. The foaming gas is most preferably air because it is inexpensive and easily available. However, if desired, other gases that are gaseous at ambient conditions and that are substantially inert or non-reactive to any component of the liquid phase may be used. Other gases include, for example, nitrogen, carbon dioxide, and fluorocarbons that are normally gases at ambient temperature. This inert gas is incorporated into the liquid phase by mechanically stirring the liquid phase with a high shear device such as a Hobart mixer or Oakes mixer. This gas can be introduced under pressure in the normal operation of an Oaks mixer or, in the case of a Hobart mixer, can be drawn in by stirring or frothing from the overlying atmosphere. The mechanical agitation operation may be performed at standard pressures, for example, pressures below 100-200 pounds per square inch (689-1379 kPa). Easily available mixing equipment can be used and no special equipment is required. The amount of inert gas stirred into the liquid phase to control the desired density of bubbles is controlled by a gas flow meter. Mechanical agitation is carried out for a period suitable to obtain the desired pre-curing foam density, for example over a few seconds with an Oaks mixer or 3 to 30 minutes with a Hobart mixer. Foams that appear in the mechanical stirring operation are substantially chemically stable and structurally stable, but can be easily processed at ambient temperatures, for example 10 ° C to 40 ° C.

  After foaming, the reactive mixture is transferred at a controlled rate via a hose or other conduit and deposited on the first support. For convenience, this first support can be referred to as the “lower support” and is generally a movable support from which the cured foam may or may not be easily peeled off. is there. A second support, also referred to herein as a “surface protective layer” or “upper support”, is disposed on the reactive mixture. This upper support is also a movable support that may or may not be easily peeled off from the cured foam. This upper support can be applied almost simultaneously with foaming. Prior to application of the upper support, the foam can be spread into a layer of the desired thickness by a doctor blade or other suitable spreader. Alternatively, the arrangement of the upper support may be utilized to expand the foam and adjust the foam layer to the desired thickness. In still other embodiments, a coater can be used after placement of the upper support to adjust the height of the foam. After application of the upper support, the foamed foam is expanded by the action of a physical foaming agent or a chemical foaming agent.

  In practice, the support can be unwound from a supply roll and finally unwound onto a take-up roll separated from the cured polyurethane foam. The choice of material for the upper and lower supports depends on factors such as the desired degree of support and flexibility, the desired peelability from the cured foam, cost, and similar considerations. Paper, a thin metal plate such as stainless steel, or a polymer film such as polyethylene terephthalate or silicone may be used. This material can be coated with a release coating. In one embodiment, the support may be coated with a material intended to be transferred to the surface of the cured polyurethane foam, such as a polyurethane film that can be peeled from the support. Fibrous webs or other fillers may be placed on the surface of the support, thereby ultimately being incorporated into the cured foam. In other embodiments, the foam is cured on one or both of the supports. Thus, one or both of the supports become part of the final product instead of being separated from the foam and rewound onto a take-up roll. Alternatively, a conveyor belt can be used as the lower support. The support may have a flat surface or a textured surface.

In a specific embodiment, a skin layer is provided on the surface of the foam. Thereby, the adhesion to the object to be sealed can be increased, so that the sealing performance can be increased.
In one particular embodiment, the substrate film 14 is cured and bonded to the foamed polyurethane sheet 12, i.e., the polyurethane sheet, in order to increase the structural strength of the article, such as the seal member 10, and improve the handleability of the product. As described below with respect to the manufacturing method, the substrate film 14 can also serve as a transfer means for the foaming reactive composition in the manufacturing apparatus 30. Accordingly, the base film 14 preferably includes any resin having low heat shrinkage, such as polyethylene terephthalate (PET), which has a physical strength capable of resisting the tension applied by the roll machine 32, and heating means. Resistant to heat applied by 38. Furthermore, although it is preferable to use PET especially from the viewpoint of cost, a film containing a resin such as polyolefin, polyester, polyamide, or polyvinyl chloride can also be used. Depending on the quality of the material, the thickness of the base film or the lower support 14 may be 10 to 500 μm, preferably 25 to 125 μm. Such a thickness does not adversely affect the sealing performance of the article even when the base film 14 is bonded to the foamed polyurethane sheet 12.

  The assembly of the support and the foam layer (after any expansion) is transferred to a heating zone for curing the polyurethane foam. Depending on the composition of the foam material, the temperature is maintained in a range suitable for curing the foam, for example 90 ° C. to 220 ° C. Different temperatures can be established to form an integral skin on the outer surface of the foam or to add a relatively thick layer to the foam.

  After the foam is heated and cured, it can then be transferred to a cooling zone that is cooled by a suitable cooling device such as a fan. If necessary, the support can be removed and the foam can be wound on a roll. Alternatively, the foam can be subjected to further processing, for example lamination (bonding using heat and pressure) to one or both of the support layers.

  A preferable example of a manufacturing method of an article including a foamed polyurethane sheet, for example, a manufacturing apparatus of a seal member, and an article using the manufacturing apparatus will be described below. As shown in FIG. 3, the method for manufacturing a polyurethane foam sheet includes a step S1 of preparing and preparing a raw material, a step S2 of supplying and molding the raw material, a heating step S3, and a final step S4. This foamed polyurethane sheet is preferably manufactured by a manufacturing apparatus 30 shown in FIG. The manufacturing apparatus 30 includes a mixing unit 31, a roll mechanism 32, a discharge nozzle 34, a surface protection mechanism 35, a thickness control unit 36 such as a roll or plate type knife coater, and a heating unit 38 such as a tunnel type heating furnace. In the mixing part 31, the main raw material (polyisocyanate component and reactive hydrogen-containing component), various auxiliary raw materials, foaming gas and the like are mixed with each other, and the reactive composition M is prepared by mechanical flossing. The roll mechanism 32 includes a supply roll 32a and a product collection roll 32b. The supply roll 32a serves as a moving means for the reactive composition M when the base film 14, for example, a PET film is driven by a drive source (not shown). The discharge nozzle 34 supplies the reactive composition M onto the base film 14. The surface protection mechanism 35 includes a supply roll 35a and a recovery roll 35b. The thickness control means 36 is disposed near the base film 14 on the downstream side of the supply roll 35a (a roll as shown in the figure). That is, the supply roll 35a and the collection roll 35b are driven by a driving means (not shown), whereby the surface protection film 16 is removed from the upper surface of the base film 14 via the roll of the thickness control means 36 and the guide roll 37. And is rewound onto the collection roll 35b. The surface protection film 16 can also comprise a PET film or other film, passing between the reactive composition M supplied on the substrate film 14 and the thickness control means 36, thereby increasing the thickness. The control means 36 is prevented from coming into direct contact with the reactive composition M on the downstream side of the discharge nozzle 34. The thickness control unit 36 controls the reactive composition M to a predetermined thickness on the downstream side of the discharge nozzle 34. The heating means 38 is provided on the downstream side of the thickness control means 36. The reactive composition M is reacted and cured on a flat surface, but may be reacted and cured in a mold or on release paper as necessary.

  The roll mechanism 32 is a mechanism that supplies the base film 14 to the production line while applying tension to the base film 14 and collects the obtained polyurethane foam sheet. The base film 14 is wound around the supply roll 32a, and the base film 14 is delivered under control. The discharge nozzle 34 supplies the reactive composition M onto the substrate film 14 to be transferred under control, and the upper end thereof is connected to the mixing unit 31. Step S1 of preparing and preparing the raw material to be carried out in the mixing unit 31 is a step of preparing and mixing the reactive composition M for the foamed polyurethane sheet 12 from the main raw material and each auxiliary raw material.

  In this step, as described above, the surface protection film 16 prevents the thickness control means 36 from contacting the reactive composition M supplied on the base film 14. Further, like the base film 14, the surface protective film 16 preferably comprises any resin having low heat shrinkage, such as PET, which resists the smooth surface, tension applied by the surface protection mechanism 35. It has a physical strength to be obtained and resistance to heat applied by the heating means 38. Furthermore, in one embodiment, the foamed polyurethane sheet 12 produced by heating and curing the reactive composition M after the reactive composition M has passed through the heating means 38 and its surface has been flattened. The surface protective film 16 is peeled from the surface. Therefore, a release agent such as a silicone material is applied in advance to the contact area of the surface protective film 16 with the reactive composition M. Alternatively, paper with a release coating may be used.

  The thickness control means 36 forms the reactive composition M released on the base film 14 into a sheet material having a required thickness, and thus a roll is used in this example. When the reactive composition M passes through the thickness control means 36, the step S2 for supplying and molding the raw materials is completed. When only mechanical floss is used, the thickness of the polyurethane foam sheet produced by heating and curing the reactive composition M is set by the thickness control means. Therefore, the reactive composition M before heating (curing) is prepared according to the mechanical floss method, but the thickness is significantly different from the foamed polyurethane sheet after heating (curing). Therefore, the cured foam produced from the reactive composition M has a thickness set by the thickness control means 36. However, it should be noted that if both mechanical flossing and expansion (chemical or physical foaming) are used, the thickness control means 36 sets the initial thickness of the foam. Subsequent expansion of the cast foam usually results in an increase in thickness, thus resulting in a cured foam having an increased thickness.

  When the reactive composition M passes through the heating means 38, the heating step S3 is completed. In one embodiment, when the reactive composition M is heated and cured on the base film 14, the polyurethane foam sheet 12 and the base film 14 effectively utilize the adhesive effect of the reactive composition M, Thereby, the foamed polyurethane sheet 12 is firmly bonded to the base film 14. That is, when the reactive composition M is cured while being in contact with the film 14, the foamed polyurethane sheet 12 and the base film 14 are bonded together. In the final step S4, a long foamed polyurethane sheet 12 manufactured in each of the steps S1 to S3 is obtained, and if necessary, it is punched into the shape of the foamed polyurethane sheet, which becomes the final product, and further final inspection is performed. Is done. During the final inspection, the foamed polyurethane sheet 12 may be wound and collected by the product collection roll 32b and shipped as it is. In such a production form, the length of the polyurethane foam sheet 12 is preferably 5 meters or more. In this case, it is possible to continuously perform processing for making the long foamed polyurethane sheet 12 into a required shape and processing such as tape application and punching, thereby improving productivity. Therefore, reduction of manufacturing cost can be expected.

  In the above-described embodiment, the base film 14 forming a part of the foamed polyurethane sheet is directly supplied to the manufacturing process, whereby the base film 14 is also used as a support film. However, the present invention is not limited to this. For example, as in the manufacturing apparatuses 50 and 60 shown in FIGS. 5 and 6, a step of separately preparing the support film 18 and a step of laminating the base film 14 using the pressure roll 70 or the like (see FIG. 5). And the method including the step of previously laminating the base film 14 on the support film 18 (see FIG. 6) so that the support film 18 can be easily peeled off. Can be manufactured. In this case, the role as a support for moving the reactive composition M by applying tension can be cut off, whereby the thickness of the base film 14 can be made thinner, and a less expensive material. Cost reduction by adopting can be expected.

  Therefore, in one embodiment, the thickness of the reactive composition M is controlled by the thickness control means 36 through the surface protective film 16, thereby controlling the thickness of the foamed polyurethane sheet. Furthermore, the surface of the reactive composition M is protected from being roughened, and the surface shape becomes flat. However, the surface protective film 16 is not essential. For example, a release agent can be continuously supplied to the surface of the roll so as to enhance the peelability between the roll of the thickness control means 36 and the reactive composition M, whereby the surface of the reactive composition M Can be protected from roughing. In this case, the film 16 for surface protection is not necessary, thereby reducing troubles during production and expecting cost reduction.

  Furthermore, the reactive composition M does not necessarily have to be provided on the base film 14. For example, the following method can be used, which includes supplying both the base film 14 and the surface protection film 16 from the top to the bottom, and a slight gap between the two films 14 and 16. The reactive composition M is supplied to the substrate and the thickness thereof is controlled, and the reactive composition M is maintained in the gap while the viscosity of the reactive composition M itself is utilized to the maximum. Applying heat to the composition M to cure it. In this case, even when the viscosity of the reactive composition M is not sufficiently high, the reactive composition M simply moves downward and moves according to the manufacturing process, and further the thickness of the reactive composition M, that is, the reactive composition. The space filled with the object M is substantially limited by the base film 14 and the surface protection film 16, thereby causing no problem in terms of manufacturing process and quality, and further increasing the degree of freedom of installation of the manufacturing apparatus. .

When only mechanical floss is used, the density of the polyurethane foam sheet 12 thus obtained is 100 to 250 kg / m ³ and the thickness is 0.3 to 3.0 mm. Therefore, by achieving such density, 50% CLD becomes 0.003 to 0.025 MPa and 75% CLD becomes 0.02 to 0.40 MPa. Further, the relative dielectric constant measured at frequencies of 10 kHz, 100 kHz and 1 MHz is 1 to 2.0.

  The term “50% CLD” indicates the load required when the foamed polyurethane sheet 12 is physically compressed by 50%, that is, the hardness of the foamed polyurethane sheet 12 when physically compressed by 50%. The term “CLD” indicates the load required when the expanded polyurethane sheet 12 is physically compressed by 75%, that is, the hardness of the expanded polyurethane sheet 12 when physically compressed by 75%. When these two values are higher than the above-mentioned preferred range, the foamed polyurethane sheet 12 is excessively hard when physically compressed by 50% or 75%, and therefore is less flexible, so that the foamed polyurethane sheet 12 has a sealing property. Cannot be achieved sufficiently. Furthermore, the load applied to the housing is excessively increased, and thus when the final product is used, at least one of distortion, cracking, chipping, and other physical defects may occur in the housing. On the other hand, when the values of 50% CLD and 75% CLD are lower than the above-mentioned preferable range, it is difficult to mold the polyurethane foam sheet 12.

Since it is difficult to homogeneously mix the foaming gas and the resin raw material (reactive composition) in the production process, when only the mechanical floss method is used, a foam having a density of less than 100 kg / m ³ is used. It turned out to be difficult to manufacture. Furthermore, the bubbles forming the cells are not maintained stably, and cell roughening occurs, thereby causing at least one of the shape and size of the cells to be nonuniform, leading to the appearance of voids (cell roughening, large voids). Was observed. As a result, sufficient sealing performance is inhibited. When the density of the foam produced using only mechanical floss exceeds 250 kg / m ³ , the preferred values of the aforementioned 50% CLD, 75% CLD and relative dielectric constant cannot be obtained.

  When the thickness is less than 0.3 mm, it is difficult to achieve the desired elasticity, and sufficient sealability cannot be achieved. In consideration of use in a device that requires space saving, such as a cellular phone, the upper limit of the thickness is 3 mm. Furthermore, when the gap of the fitting structure of the casing of the mobile phone is, for example, 0.25 mm and 0.5 mm, the seal member of the present invention having a thickness set to 1 mm is physically compressed by 50%. It is compressed to 0.5 mm while maintaining its sealing property, and when it is physically compressed by 75%, it is compressed to 0.25 mm while maintaining its sealing property to provide a suitable sealing member.

Unexpectedly, a polyurethane foam having advantageous properties over a wider range of densities and a wider range of thickness when mechanical floss and chemical or physical foam are used in combination with the upper support. It became clear that the production of Without being bound by theory, it is believed that the upper support limits the diffusion of gas generated by the blowing agent from the reactive composition. The density of the foam formed using mechanical floss and expansion with the upper support is 50-400 kg / m ³ , specifically 60-250 kg / m ³ , more specifically 70-200 kg / m ^3. More specifically, it can be 70 to 150 kg / m ³ . Moreover, the thickness of such a foam is 0.3 to 13 mm, specifically 0.3 to 9 mm, more specifically 0.3 to 5 mm, and more specifically 0.3 to 3 mm. . Such foam has excellent physical properties. For example, such a foam can have a 50% CLD of 0.003 to 0.025 MPa and a 75% CLD of 0.02 to 0.40 MPa. Furthermore, the relative dielectric constant measured over frequencies of 10 kHz, 100 kHz, and 1 MHz is 1 to 2.0.

In particular, foams made using mechanical and chemical floss and an upper support can have a thickness of 0.3 to 5 mm and a density of 320 to 400 kg / m ³ . Alternatively, the foam can have a thickness of 0.5 to 13 mm and a density of 50 to 250 kg / m ³ . It is difficult to control the thickness of the foam to less than 0.3 mm. A foam having a thickness exceeding 13 mm is not useful as a gasket for a small electronic device such as a mobile phone. In a foam having a density of less than 50 kg / m ³ , voids may be formed to an unacceptable level. Foams with a density greater than 400 kg / m ³ do not have other desirable properties such as 50% CLD. It is also difficult to control the thickness of the foam having a thickness of less than 5.0 mm and a density of less than 320 kg / m ³ .

  The term “relative permittivity” used in the present application means a value obtained by dividing the ratio between the electric flux density and the electric field density by the vacuum permittivity, and the minimum value of the relative permittivity is theoretically 1. That is, as the object to be measured (for example, the foam structure constituting the foamed polyurethane sheet 12 in the present invention) is sparser, the relative dielectric constant becomes lower. Therefore, in the present invention, by reducing the density of the polyurethane foam sheet and increasing the cell ratio, the relative dielectric constants at frequencies of 10 kHz, 100 kHz, and 1 MHz are 1 to 2.0, respectively. This is because if the relative dielectric constant exceeds 2.0, the insulation performance of the foamed polyurethane sheet is inferior, whereby sufficient insulation cannot be exhibited. The density of the structure of the polyurethane foam constituting the foamed polyurethane sheet 12 can be basically expressed by the cell ratio. When the density of the foam is lowered, the bubble ratio can be increased. Specifically, the bubble ratio is increased by increasing the mixing ratio of a foaming gas mixed in the reactive composition M, for example, an inert gas such as nitrogen. The bubble rate is 76% by volume or more.

  In order to impart good mechanical properties to the foam, particularly good sealing properties to the foamed polyurethane sheet, the cell diameter of the foam is 20 to 500 μm, preferably 20 to 300 μm. When this value exceeds 500 μm, at least one of the dustproof performance and the light shielding effect of the foam deteriorates. Furthermore, the sealing property of a foam becomes high, so that the cell diameter of a foam becomes small. On the other hand, if the cell diameter of the foam is less than 20 μm, it is difficult to control the cell diameter, which is not practical.

The invention is further illustrated by the following non-limiting examples.
In the following examples, the following polyols were used.
Polyether polyol-A: trade name “GP-3000”; Sanyo Chemical Industries, Ltd. (average molecular weight is 3000, hydroxyl value is 56.0, EO content is 0%); and polyether polyol B: Trade name “FA-103”; Sanyo Chemical Industries, Ltd. (molecular weight is 3300, hydroxyl value is 50.0, EO content is 80%).

Furthermore, the measuring method and conditions are as follows.
Density: The weight of each sample was measured with an electronic balance, and then the density was calculated using the following formula.
Density (kg / m ³ ) = [Sample Weight (kg)] / [Sample Volume (m ³ )]
50% CLD: Using a compression tester, the sample was compressed to a thickness of 50% of the original thickness at a compression rate of 1 mm / min, and then the load was measured. And 50% CLD was calculated using the following formula.

50% CLD (MPa) = [50% compression load (N)] / [sample area (cm ² )]
75% CLD: Using a compression tester, the sample was compressed to 75% of its original thickness at a compression rate of 1 mm / min and then the load was measured. And 75% CLD was calculated using the following formula.

75% CLD (MPa) = [Load at 75% compression (N)] / [Sample area (cm ² )]
Relative permittivity: Product name “HP4192A”; The relative permittivity at a predetermined frequency was measured using a relative permittivity measuring instrument of Hewlett-Packard Development Company.

Example 1 Density, 50% CLD, and 75% CLD
100 parts by weight of polyether polyol A, 3 parts by weight of a crosslinking agent (1,4-butanol), 20 parts by weight of a thickener (aluminum hydroxide), 0.1 parts by weight of a metal catalyst (2-ethylhexane) Tin oxide) and 3 parts by weight of a foam stabilizer (silicone material; including a solvent for dilution) to obtain a mixture. In this mixture, nitrogen (foaming gas) and a polyisocyanate (trade name “C-”) were set so that the isocyanate index was 0.9 to 1.1 so that the ratio described in Table 1 was obtained. 1130 "; Nippon Polyurethane Industry Co., Ltd .; Crude MDI, NCO content: 31%) was mixed at a flow rate of 0.1 NL / min, and the mixture was sheared to produce a reactive composition (" foam reactive composition M " )). The foam reactive composition M is supplied from a discharge nozzle 34 onto a base film (made of PET) having a predetermined thickness that is continuously supplied from a supply roll 32a in a state where tension is applied to the roll mechanism 32. The foam reactive composition M was set to a predetermined thickness by the thickness control means 36. Thereafter, the reactive composition M is heated by the heating means 38 at a temperature of 150 ° C. to 200 ° C. for 1 to 3 minutes, thereby causing the reaction and curing of the reactive composition M to proceed to obtain the foamed polyurethane sheet 12, Was recovered by the product recovery roll 32b. The obtained polyurethane foam sheet 12 was punched into a predetermined shape and subjected to other processing treatments to obtain a polyurethane foam sheet.

  Then, the base film is peeled off from the sealing members of Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2, and the thickness required for measuring the dielectric constant × 150 mm × 50 mm Rectangular specimens, as well as circular samples of thickness x 150 mm required to measure 50% CLD and 75% CLD. Using these samples, the relative dielectric constant at each frequency of 10 kHz, 100 kHz, and 1 MHz, and 50% CLD (MPa) and 75% CLD (MPa) were measured. Based on the measured results, the seal of the present invention was measured. The applicability as a member was evaluated.

  All the results of Example 1 are shown in Table 1. From Table 1, it was confirmed that by setting the density within the range set in the present invention, the values of 50% CLD and 75% CLD sufficiently satisfy the sealing properties. Furthermore, by setting the EO content rate within the range set in the present invention, it was confirmed that the relative dielectric constant at each frequency of 10 kHz, 100 kHz, and 1 MHz was a low value in the range of 1 to 2.0.

（実施例２）比誘電率に対するＥＯ含有率の効果の測定
表２に記載される割合のポリエーテルポリオールＡ及びポリエーテルポリオールＢの１００重量部を、３重量部の架橋剤（１，４−ブタノール）、２０重量部の増粘剤（水酸化アルミニウム）、０．１重量部の金属触媒（２−エチルヘキサン酸スズ）、及び３重量部の整泡剤（シリコーン材料；希釈用の溶媒を含む）と混合して混合物を得た。この混合物に、表２に記載される割合となるように、窒素（造泡用気体）、及びイソシアネートインデックスが０．９〜１．１となるようにに設定されたポリイソシアネート（クルードＭＤＩ、ＮＣＯ含有率：３１％）を０．１ＮＬ／分の流速で混合し、その混合物を剪断して反応性組成物Ｍを得た。その後、実施例１に従って、実施例２−１及び比較例２−１〜２−３の試験片を製造し、比誘電率、５０％ＣＬＤ及び７５％ＣＬＤを測定した。

Example 2 Measurement of Effect of EO Content Ratio on Dielectric Constant 100 parts by weight of polyether polyol A and polyether polyol B in the proportions shown in Table 2 were added to 3 parts by weight of a crosslinking agent (1,4- Butanol), 20 parts by weight thickener (aluminum hydroxide), 0.1 parts by weight metal catalyst (tin 2-ethylhexanoate), and 3 parts by weight foam stabilizer (silicone material; solvent for dilution). To obtain a mixture. In this mixture, nitrogen (foaming gas) and polyisocyanate (crude MDI, NCO) set so that the isocyanate index is 0.9 to 1.1 so as to have the ratio described in Table 2 Content: 31%) was mixed at a flow rate of 0.1 NL / min, and the mixture was sheared to obtain a reactive composition M. Then, according to Example 1, the test piece of Example 2-1 and Comparative Examples 2-1 to 2-3 was manufactured, and the relative dielectric constant, 50% CLD, and 75% CLD were measured.

  All the results of Example 2 are shown in Table 2. From Table 2, it was confirmed that the relative dielectric constant at each frequency of 10 kHz, 100 kHz, and 1 MHz is a low value in the range of 1 to 2.0 by setting the EO content in the range set in the present invention.

^＊Ａ／Ｂは、ポリエーテルポリオールＡとポリエーテルポリオールＢとの重量比を表す。

^* A / B represents the weight ratio of polyether polyol A and polyether polyol B.

As described above, in the sealing member and the manufacturing method thereof according to the present invention, a polyurethane foam raw material prepared by mixing a predetermined amount of resin raw material and foaming gas is used, and the density of the foamed polyurethane sheet is reduced. The range of 100 to 250 kg / m ³ is set, whereby the compression load at the 50% deflection point of the polyurethane foam sheet is in the range of 0.003 to 0.025 MPa, and the compression load at the 75% deflection point is 0.02 It will be in the range of ~ 0.40 MPa. Therefore, a sealing member having sufficient sealing performance in the case of a high compression ratio can be manufactured. Furthermore, when the density is set in the above range, there is an advantageous effect that the relative permittivity of the seal member can be reduced. Therefore, this seal member can be appropriately used even for a housing that has high conductivity and easily flows current, and thus may cause defects such as generation of electromagnetic waves.

(Example 3)
The following examples show polyurethane foams made from foamed compositions with or without water. For each foam, the polyol, catalyst, and water (if used) were mixed and stored in dry nitrogen with stirring in a storage tank. The mixture was then pumped into an Oaks type high shear mixing head at a controlled flow rate. The isocyanate component, surfactant and pigment mixture were also separately pumped into the mixing head at a controlled flow rate and a flow rate ratio appropriate for the polyol mixture flow rate. A flow meter was used to measure and adjust the flow rates of the various raw materials. Dry air is introduced into the mixing head using a gas flow controller and the foam density before curing is 160, 320, 481, 641, 801 and 961 kg / m ³ (10, 20, 30, 40, 50 and 60 pcf) The air flow rate was adjusted so that each was obtained.

  Each raw material was mixed with a high shear mixer to prepare a foamed composition before curing, and then pumped from a rigid nozzle via a flexible hose. Next, the foamed composition before curing was cast on a release paper provided with a coating dried by an infrared dryer immediately before the foamed composition was introduced. By doing this, water that might have been present on the paper was not involved in the reaction. The release paper is 30.5 cm (12 inches) wide and is controlled by the machine, two controlled speeds of 152 cm / min (5 ft / min (FPM)) and 457 cm / min (15 FPM) the other Pulled out. The paper lower layer, cast foam and upper layer were then passed under a plate knife (KOP) coater. KOP was used to control the initial thickness of the final product to 2.54 mm (100 mils). The width of the cast foam layer was 20 to 25.4 cm (8 to 10 inches).

  The release paper with this coating was then passed through a curing section consisting of a heated plate maintained at 120 ° C. to 190 ° C. by a series of thermocouples, controller and heating element. A series of top plates were maintained at 220 ° C. The cured product was then passed through an air-cooled section and a series of drive rolls and taken up with a take-up roll.

FIG. 7 shows the density of cured foams made from various blended raw materials with or without water. It can be clearly seen that the foam produced from the raw material containing no water has almost the same density as the raw material used for its production. For example, the density of water free from the mixed material of 320kg ^/ m 3 (20pcf), foam density 320kg ^/ m 3 (20pcf) was produced. On the other hand, from the blended raw material containing water, a foam having a significantly lower density than the blended raw material used for the production was obtained. For example, the density is from mixed material containing water of 320kg ^/ m 3 (20pcf), the density of the cured polyurethane foam 192kg ^/ m 3 (12pcf) was obtained. Thus, it can be clearly seen that when water in the blended raw material is used, a foam is produced that has a significantly lower density than that produced from the blended raw material that does not contain water.

Example 4
The data shown in FIG. 8 shows the change in foam density before curing for a 2.5 mm thick polyurethane foam made from a blended raw material containing 0.25 parts water as described or a blended raw material not containing water. The change of the foam density with respect to is represented. In addition, some foams were made using a top support (TC), and some foams were made without a top support (no TC). Each foam was made substantially as described above.

From FIG. 8, it can be seen that the foam produced from the raw material containing no water has almost the same density as the foam used for the production. For example, the foam density prior to curing with no water from mixed material of 320kg ^/ m 3 (20pcf), to produce a foam of density 320kg ^/ m 3 (20pcf). If no water is used for the foam, there appears to be no difference regardless of the presence of the upper support. On the other hand, from the blended raw material containing water, a foam having a significantly lower density than the blended raw material used for the production was obtained. Foams made from blended raw materials containing water using the upper support have the greatest density reduction. For example, a polyurethane foam having a density after curing of 160 kg / m ³ (10 pcf) was obtained from a blended raw material containing water having a foam density before curing of 320 kg / m ³ (20 pcf) using the upper support. . Accordingly, when water is used in the foaming mixture and the upper support is used, a foam is produced that is substantially lower in density than that produced from a blended raw material that does not contain water and does not use the upper support.

(Example 5)
Tables 3 and 4 below show the effect of using a combination of chemical blowing agent (water) and mechanical floss, and cure in the presence of the upper support. The formulations and procedures described above can be used. Table 3 shows the effect of using a combination of chemical blowing agent (water) and mechanical floss, and curing in the presence of the upper support. Table 4 shows the curing in the presence of mechanical floss only and the upper support.

  In Tables 3 and 4, “O” indicates that the foam is acceptable for use as a gasket material, that is, the foam can be formed with a uniform thickness, and the cell structure is an electronic device such as a mobile phone. Means acceptable for use in equipment. “V” means that the foam thickness may be controlled to an acceptable level, but one or more voids are formed in the foam. The presence of voids is undesirable from a customer perspective. “X” means that the thickness of the foam varies and one or more voids are formed in the foam.

本願では、同じ特性又は同じ成分の量を示す全ての範囲の両端はそれぞれ独立して、記述された端点自体を含む。

In this application, both ends of all ranges exhibiting the same property or amount of the same component each independently include the described endpoint itself.

The graph which shows the relationship between foaming density and foaming viscosity. The schematic perspective view which notches and shows a part of sealing member which concerns on suitable embodiment of this invention. The flowchart which shows the manufacturing method of the sealing member of embodiment. Schematic which shows an example of the manufacturing apparatus which manufactures the sealing member of embodiment. Schematic which shows an example of the manufacturing apparatus which manufactures the sealing member in the example of a change. Schematic which shows an example of the manufacturing apparatus which manufactures the sealing member in another modification. The graph which shows the effect of the addition of water with respect to the relationship between a foam density and the foam density before hardening. The graph which shows the effect of the addition of water and use of an upper support body with respect to the relationship between a foam density and the foam density before hardening.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Seal member as goods, 12 ... Foam polyurethane layer as low density polyurethane foam, 14 ... Base film as 1st support body, 16 ... Surface protection film as 2nd support body, 36 ... Thickness adjustment Thickness control means as means.

Claims (13)

A method for producing a low-density polyurethane foam used for a sealing member,
Reactive polyurethane-forming composition comprising an isocyanate-containing component, an active hydrogen-containing component that reacts with the isocyanate-containing component, a water-containing foaming agent, a surfactant, and a catalyst system that delays curing of the foam according to a mechanical froth method A step of mixing and stirring the foam-forming gas to adjust the foam composition;
Casting the foamed composition on a first support;
Disposing a second support on the surface of the cast foam composition opposite the first support;
After expanding and curing the foamed composition, the second support is peeled off from the surface, and a polyurethane foam layer having a density of 50 to 250 kg / m ³ and a thickness of 0.5 to 13 mm. A process for producing a low-density polyurethane foam comprising the step of: The method according to claim 1, wherein the polyurethane foam layer is a polyurethane foam layer having a 50% CLD of 0.025 MPa or less and a 75% CLD of 0.40 MPa or less. The method of claim 1, wherein the second support imparts a smooth surface finish to the polyurethane foam. The method according to claim 1, further comprising a release layer on at least one surface of the first support, wherein the foamed reactive polyurethane-forming composition contacts the release layer of the first support. The method of claim 1, further comprising passing the first support, the foam composition and the second support through a thickness adjusting means. The method of claim 1, wherein the first support is bonded to a polyurethane foam layer cured in contact. The method according to claim 1, wherein the active hydrogen-containing component contains a polyether polyol, and the ethylene oxide content of the polyether polyol is 20% by weight or less based on the weight of the polyol. The method of claim 1, wherein the blowing agent comprises a chemical blowing agent. The method of claim 1, wherein the blowing agent comprises a physical blowing agent. The physical blowing agent is 1,1-dichloro-1-fluoroethane, 1,1-dichloro-2,2,2-trifluoro-ethane, monochlorodifluoromethane, 1-chloro-1,1-difluoroethane; 1,1,3,3,3-hexafluoropropane, 2,2,4,4-tetrafluorobutane, 1,1,1,3,3,3-hexafluoro-2-methylpropane, 1,1, 1,3,3-pentafluoropropane, 1,1,1,2,2-pentafluoropropane, 1,1,1,2,3-pentafluoropropane, 1,1,2,3,3-pentafluoro Propane, 1,1,2,2,3-pentafluoropropane, 1,1,1,3,3,4-hexafluorobutane, 1,1,1,3,3-pentafluorobutane, 1,1, 1,4,4,4-hexafluoro 1,1,1,4,4-pentafluorobutane, 1,1,2,2,3,3-hexafluoropropane, 1,1,1,2,3,3-hexafluoropropane, 1, 1-difluoroethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, methyl-1,1,1-trifluoroethyl ether, difluoromethyl-1,1,1-trifluoroethyl ether; n-pentane The method according to claim 9, which is a combination comprising at least one of the above-mentioned blowing agents. The method of claim 1, wherein the catalyst comprises a metal acetylacetonate. The method according to claim 1, wherein the polyurethane foam layer includes cells having an average cell diameter of 20 to 500 μm. The method according to claim 1, wherein the polyurethane foam layer has a relative dielectric constant of 1 to 2.0 at each frequency of 10 kHz, 100 kHz, and 1 MHz .

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