JP3558273B2 - Method for producing polyurethane foam and polishing sheet - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a polyurethane foam having uniform fine cells. The microcellular polyurethane foam of the present invention can be suitably used as a polishing material suitable for polishing resin, glass for manufacturing lenses such as lenses, quartz, semiconductors, electronic substrates, optical substrates, and the like. The present invention also relates to a polishing sheet suitable as a polishing material, which is obtained by appropriately cutting the polyurethane foam obtained by the above-mentioned production method.
[0002]
[Prior art]
Techniques for producing polyurethane foam include a method of adding and dispersing a low-boiling organic solvent such as chlorofluorocarbon and methylene chloride to a foam-forming raw material composition, foaming the polymer by vaporization by heat of polymerization, and a foam-forming raw material. A method of adding and dispersing water to a composition and foaming a polymer by carbon dioxide gas generated by a reaction between an isocyanate group and water is well known. The foam obtained by these methods has an average bubble diameter (cell diameter) of 100 μm as a lower limit, and it is difficult to obtain a foam having finer and uniform cells.
[0003]
The following method is known as a method for producing a polyurethane foam having fine cells.
(1) After dispersing solvent-soluble fine particles in a polyurethane polymer and molding into a predetermined shape, the molded article is immersed in a solvent in which the fine particles dissolve but the polyurethane polymer does not dissolve, and the fine particles are dissolved and removed to remove the porous polyurethane. A method of forming a resin, that is, a foam.
(2) A method of dispersing a minute hollow foam in a raw material composition for forming a polyurethane resin.
[0004]
[Problems to be solved by the invention]
However, according to the above method (1), a large amount of solvent is required, and a solvent containing a fine particle forming material needs to be treated, which is costly. Moreover, the obtained foam is only open cells, and cannot be used for applications requiring rigidity, and the applications are limited. In addition, an elution step and a step of drying the solvent are also required, and there is a problem that it takes a long time to produce a molded article having a large thickness.
[0005]
On the other hand, according to the technique (2), a void having a diameter larger than the diameter of a micro hollow foam called an air void having a diameter of 500 μm or more is formed in order to entrain air as bubbles when dispersing the micro hollow foam. appear. Silicon for manufacturing semiconductors and the like, and polishing sheets used for the production of electronic substrates are required to have high-precision polishing in accordance with the increase in the density of circuits to be formed. Required. Therefore, when using a micro hollow foam, a vacuum defoaming step is indispensable to prevent air voids, and because the micro hollow foam is expensive, it is required to be a foam required for an abrasive sheet. Requires the use of a large amount of fine hollow foams, which results in high material costs, complicated processes, and high production costs as a whole.
[0006]
An object of the present invention is to have uniform fine bubbles without using a chemically reactive foaming agent such as water or a vapor-expandable foaming agent such as chlorofluorocarbon, a solvent-soluble substance, etc., reduce air voids, and reduce manufacturing costs. An object of the present invention is to provide a method for producing a polyurethane foam.
[0007]
[Means for Solving the Problems]
The inventor of the present invention included a surfactant and a resin balloon in a first component containing an isocyanate prepolymer, which is a raw material liquid for producing polyurethane, and stirred these liquids vigorously in the presence of a non-reactive gas. It becomes a bubble / balloon dispersion containing fine non-reactive gas bubbles and resin balloons, and a chain extender is added and mixed with this to cause a polymerization reaction. It has been found that a polyurethane foam having a fine cell structure can be obtained, and the present invention has been completed.
[0008]
The present invention relates to a first component containing an isocyanate prepolymer, a resin balloon, and a silicon-based nonionic surfactant having no hydroxyl group so as to be 5 to 50% by weight in a microcellular polyurethane foam (hereinafter simply referred to as “surfactant”). ), And the first component is stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles to form a bubble / resin balloon dispersion. The present invention relates to a method for producing a microcellular polyurethane foam , comprising mixing a balloon dispersion with a chain extender having a molecular weight of 500 or less and curing the mixture.
[0009]
The use of a resin balloon stabilizes fine bubbles generated by the dispersion of non-reactive gas, forms a uniform foam, and increases the rigidity of the foam sheet while having the necessary flexibility. Suitable effects can be obtained. Further, the surfactant of the present invention has an action of miniaturizing bubbles generated by dispersion of a non-reactive gas. Further, the surfactant also has an action of preventing the occurrence of aggregates of resin balloons, so-called as-is. That is, by using these resin balloons and a surfactant in combination, a polyurethane foam which can be particularly suitably used for an abrasive sheet is obtained.
[0010]
A feature of the present invention is that the specific gravity is reduced because the surrounding resin raw material liquid is in a foaming state, so that the resin balloon is prevented from rising and becoming an uneven foam.
[0011]
Here, the “non-reactive gas” refers to a gas composed of a normal-temperature gas component that does not react with an isocyanate group or an active hydrogen group. However, it may contain a small amount of water like air. Further, the gas may be positively sent into the liquid, or the gas may naturally be entrained during the stirring. Further, the fine bubbles refer to those having an average diameter of 80 μm or less. According to the method of the present invention, it is possible to manufacture an article having an average of about 10 μm. The bubble diameter can be set and controlled by appropriately selecting and adjusting conditions such as the type and amount of surfactant used, the amount of stirring, and the viscosity of the raw material used.
[0012]
The resin balloon used has a particle diameter of about 20 to 100 μm on average, which is almost the same as the bubble diameter. The amount of the resin balloon used is preferably 0.1 to 1.0% by weight based on the total amount of the polyurethane resin. When it is less than 0.1, the effect of addition cannot be obtained, and when it exceeds 1, the density of the foam decreases, which is not preferable.
[0013]
The density of the obtained foam is preferably about 0.6 to 0.9, and the hardness (ASKER C) of the foam is preferably 85 to 100. In particular, the polishing foam preferably has a hardness of 90 to 95.
[0014]
The stirring time varies depending on the performance of the stirrer, the viscosity of the reaction solution for forming the polyurethane foam, and the like, but is preferably at least 30 seconds , and more preferably about 1 minute to create a stable bubble / resin balloon dispersion. Stirring is possible as long as fluidity is ensured. This stirring time needs to be longer than the stirring time for producing a usual polyurethane foam. The diameter of the bubbles can be adjusted by the production conditions such as the surfactant to be added, the type of the resin balloon, the amount added, and the stirring time.
[0015]
In the present invention, by adding the surfactant and the resin balloon to the first component containing the isocyanate prepolymer , a polyurethane foam having excellent physical properties and having fine and uniform cells (cells) can be obtained.
[0016]
By using the isocyanate prepolymer, a foam having high rigidity and good abrasion resistance while having flexibility can be obtained, and a foam extremely suitable as a polishing sheet can be obtained.
[0017]
The isocyanate prepolymer having a molecular weight of about 800 to 5,000 is preferable because of its excellent workability and physical properties.
[0018]
The surfactant used in the present invention is a silicon-based nonionic surfactant having no hydroxyl group. By using such a surfactant, the physical properties of the polyurethane are not impaired, and the bubbles are fine and uniform. Stable polyurethane foam is obtained.
[0019]
The surfactant is added in an amount of 5 to 50% by weight in the microcellular polyurethane foam to be synthesized. If it is less than 5% by weight, a foam having fine cells can not be obtained, and if it exceeds 50% by weight, the physical properties of the polyurethane foam having fine cells deteriorate .
[0020]
The present invention also relates to a polishing sheet using the polyurethane foam obtained by the above-described production method, and has an action of releasing abrasive dust and abrasives to the surface of the sheet from the contact surface between the object to be polished and the polishing sheet outward. Characterized in that a groove is provided. The sheet may be manufactured by pouring the reaction components into a mold having a cavity having the same thickness as the thickness of the sheet intended for the polyurethane foam, or a thick block-shaped foam may be manufactured to a predetermined thickness. It may be manufactured by cutting.
[0021]
The polishing sheet has a thickness of 0.8 mm to 2.0 mm, and usually a sheet having a thickness of about 1.2 mm is used.
[0022]
Although the shape of the groove is not particularly limited, the cross section is exemplified by a rectangle, a triangle, a U-shape, a semicircle, or the like, and may have a cross-sectional area through which the fine powder passes. The grooves are arranged on the sheet surface in a concentric shape, a lattice shape, or the like. The depth of the groove depends on the thickness of the sheet and the like, but is about 1 to 2 mm.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, an isocyanate prepolymer known in the field of polyurethane can be used without limitation. The use of isocyanate prepolymers results in excellent physical properties of the resulting microcellular polyurethane foam.
[0024]
Specific examples of the organic diisocyanate that can be used as a raw material of the isocyanate prepolymer in the present invention include the following compounds.
[0025]
Aromatic diisocyanate compounds. Aliphatic diisocyanate compounds such as 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene diisocyanate, and 1,4-phenylene diisocyanate. Aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI) and hydrogenated 4,4'-diphenylmethane diisocyanate (HMDI, trade name Hylen-W, Hüls) Co., Ltd.), 1,4-cyclohexane diisocyanate (CHDI), isophorone diisocyanate (IPDI), hydrogenated m-xylylene diisocyanate ( XDI), alicyclic diisocyanates, xylylene diisocyanate over preparative such norbornane diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), etc. The above compounds may be used alone or in combination.
[0026]
In addition to the above diisocyanate compounds, trifunctional or higher polyfunctional polyisocyanate compounds can also be used. As polyfunctional isocyanate compounds, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (Bayer) or trade name duranate (manufactured by Asahi Kasei Kogyo). It is preferable to use these tri- or more functional polyisocyanate compounds by adding them to the diisocyanate compound, since they are apt to gel during the synthesis of the prepolymer when used alone.
[0027]
The isocyanate prepolymer used as the first component in the present invention is a reaction product of the above-described isocyanate compound and a polyol compound described below , and is formed of an isocyanate group (NCO) of the isocyanate compound and an active hydrogen group (H ^* ) of the polyol compound. It is an oligomer at the terminal of the NCO group which is produced by a heating reaction with an equivalent ratio NCO / H ^* in the range of 1.6 to 2.6. Equivalent ratio NCO / H ^* Is preferably in the range of 1.8 to 2.2 . The use of commercially available isocyanate prepolymers is also suitable.
[0028]
The polyol compound used for the synthesis of the isocyanate prepolymer is an organic compound having at least two or more active hydrogen atoms.
[0029]
The active hydrogen group contained in the polyol compound is a functional group containing hydrogen that reacts with an isocyanate group, and examples thereof include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH).
[0030]
The polyol compound is an oligomer having a molecular weight of about 500 to 4000 as determined by a terminal group determination method, and specific examples thereof include the following.
[0031]
1) Polyether polyol Polyether polyol is obtained by adding propylene oxide to one or more polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. Oxypropylene polyols, polyoxyethylene polyols obtained by adding ethylene oxide, butylene oxide, polyols obtained by adding styrene oxide, and the like, and tetrahydrofuran is added to the polyhydric alcohol by ring-opening polymerization. The obtained polyoxytetramethylene polyols can be exemplified. Copolymers using two or more of the above-mentioned cyclic ethers can also be used.
[0032]
2) Polyester polyol As the polyester polyol, one or two of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, trimethylolpropane, pentaerythritol or other low molecular weight polyhydric alcohols are used. Condensation of the above with one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, hydrogenated dimer acid or other low molecular dicarboxylic acids or oligomeric acids Examples include polyols such as polymers, ring-opening polymers of cyclic esters such as propiolactone, caprolactone, and valerolactone.
[0033]
3) Acrylic polyol In an acrylic copolymer, β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, β-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, β-hydroxy acrylate Hydroxyalkyl esters of acrylic acid such as pentyl or similar hydroxyalkyl esters of methacrylic acid, further glycerin, acrylic acid monoesters of polyhydric alcohols such as trimethylolpropane or methacrylic acid monoesters similar thereto, N-methylolacrylamide or An acrylic polyl having two or more hydroxyl groups in one molecule such as a copolymerized monomer of a monoethylenically unsaturated monomer having a hydroxyl group such as N-methylol methacrylamide can be used.
[0034]
In addition, a telechelic acrylic polyol can be used as the acrylic polyol. Such a telechelic acrylic polyol is obtained by polymerizing an unsaturated monomer containing a (meth) acrylic ester with an organic peroxide-containing initiator in the presence of an alcohol compound in the presence of an organic sulfonic acid compound. It is a hydroxyl group-containing acrylic polymer. As the alcohol compound, an aliphatic or alicyclic alcohol such as methanol or ethanol is preferable. When a monofunctional alcohol is used as the alcohol compound, the active hydrogen group-containing acrylic polymer obtained is substantially bifunctional, and the alcohol compound When a diol is used, the active hydrogen group-containing acrylic polymer becomes substantially tetrafunctional.
[0035]
4) Other polyols In addition, phenolic resin polyols, epoxy polyols, polybutadiene polyols, polyisoprene polyols, polyester-polyether polyols, polymer polyols obtained by vinyl addition or dispersion of polymers such as acrylonitrile and styrene, urea-dispersed polyols, carbonate polyols And the like can be used as the polyol of the present invention.
[0036]
Further, a polyol compound obtained by condensing the above exemplified polyol compound with p-aminobenzoic acid and having an active hydrogen group as an aromatic amino group can also be used.
[0037]
The chain extender used in the present invention is a compound having a molecular weight of about 500 or less. Specific examples of the chain extender include aliphatic low molecular weight glycols represented by ethylene glycol, propylene glycol, 1,4-butanediol, and trimethylolpropane, triols, and methylenebis-o-chloroaniline (MOCA). , Aromatic diamines such as dicyclohexylmethane-4,4'-diamine, 1,4-bishydroxyethoxybenzene (Cureamine H (manufactured by Ihara Chemical Co.)), m-xylylene diol (manufactured by Mitsubishi Gas Chemical Company) and the like. aromatic diols, and the like.
[0038]
The non-reactive gas used to form the microbubbles is preferably a non-flammable gas, specifically, a rare gas such as nitrogen, oxygen, carbon dioxide, helium or argon, or a mixed gas thereof. The use of air from which water has been removed by drying is most preferable in terms of cost.
[0039]
As the silicon-based nonionic surfactant used in the present invention, those capable of stably forming fine bubbles when the above-mentioned first component is stirred in the presence of a non-reactive gas can be used without limitation. is there.
[0040]
In particular, a surfactant used as a foam stabilizer in the technical field of polyurethane in that the compatibility with the isocyanate prepolymer is good, and an active hydrogen group such as a hydroxyl group that reacts with an isocyanate group as described above. Those that do not have are used. Specific examples include silicone foam stabilizers SH-190 and SH-192 (manufactured by Toray Dow Corning Silicon Co., Ltd.) and L-5340 (Nihon Unicar Co., Ltd.).
[0041]
In the present invention, as a stirring device for dispersing the non-reactive gas into fine bubbles in the first component , a known stirring device can be used without particular limitation, and specifically, a homogenizer, a Hobart mixer, a dissolver, and the like. And a two-axis planetary mixer (planetary mixer). However, a stirrer that causes a strong temperature rise by stirring is not preferable because the temperature of the mixed dispersion increases. The shape of the stirring blade of the stirring device is not particularly limited, but the use of a whipper-type stirring blade is preferable because fine bubbles can be obtained.
[0042]
In the present invention, the stirring for preparing the bubble / resin balloon dispersion and the stirring for adding and mixing the chain extender are performed, but the stirring at the subsequent stage may not be the stirring for forming bubbles in particular. The use of a stirrer that does not entrap large bubbles is preferred. As such a stirring device, a planetary mixer is suitable. Further, there is no problem even if the same agitator is used for the former stage and the latter stage, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary and use the same. .
[0043]
The conditions for producing the bubble / resin balloon dispersion are not particularly limited as long as fine bubbles are formed and a cured product of a predetermined shape is obtained, but the temperature is not lower than the melting point of the first component, the chain extender. The temperature must be lower than the temperature at which the curing reaction between the isocyanate group and the active hydrogen group does not proceed rapidly. Preferably it is 0 to 140 degreeC, More preferably, it is 10 to 120 degreeC. The curing reaction between the isocyanate group and the active hydrogen group is an exothermic reaction, and the degree of heat generation differs depending on the type and combination of the isocyanate prepolymer and the chain extender selected. If the temperature rise of the system due to the heat of reaction is large, the bubbles in the bubble / resin balloon dispersion expand, which is not preferable.If a reaction system with a small reaction heat is used or a reaction system with a large reaction heat is used, It is preferable to perform sufficient temperature control.
[0044]
In the method for producing a polyurethane foam of the present invention, heating and post-curing the foam that has reacted until the foam dispersion is poured into the mold and no longer flows has the effect of improving the physical properties of the foam. Is very suitable. The conditions in which the foam dispersion is poured into a mold and immediately placed in a heating oven to perform post-curing may be employed. Even under such conditions, heat is not immediately transmitted to the reaction components, so that the bubble diameter does not increase. The curing reaction is preferably performed at normal pressure because the bubble shape is stabilized.
[0045]
In the present invention, a catalyst that promotes the polyurethane reaction may be used. However, it is necessary to secure a sufficient stirring time for the formation of fine bubbles and a flow time for pouring into a mold having a predetermined shape, and the type and amount of the catalyst are selected in consideration of these.
[0046]
The production of the microcellular polyurethane foam of the present invention is a batch method in which each component is weighed and charged into a container and stirred, or the components are continuously supplied with a non-reactive gas to a stirring device. A continuous production system in which a molded product is manufactured by stirring and sending out a bubble / resin balloon dispersion may be used.
[0047]
In the present invention, other components may be added in addition to the polyurethane-forming raw materials. Specific examples include fillers such as resin fine powder and inorganic fine powder, catalysts or retarders for adjusting the curing reaction rate, and coloring agents such as pigments and pigments.
[0048]
【Example】
Hereinafter, examples of the present invention will be described.
(Example 1)
As a surfactant, 100 g of adiprene L-325 (isocyanate-terminated prepolymer, NCO = 9.25% manufactured by Uniroyal Corporation) melted and adjusted to 80 ° C. as a surfactant, a silicone foam stabilizer SH-192 (Toray Dow Corning Silicon Co., Ltd.) )) And 0.3 g of EXPANCEL 551DE (manufactured by Nippon Philite Co., Ltd.) as a resin balloon (first component) , and the mixture was stirred for about 5 minutes by a whipping mixer (stirring blade rotation speed = 3500 rpm). The mixture was stirred until it became a cream (meringue state) to obtain a bubble / resin balloon dispersion 1. 26.6 g of Curamine MT (methylene bis-o-chloroaniline, manufactured by Ihara Chemical Co., Ltd.) (chain extender) melted and kept at 120 ° C. while using the same whipping mixer for the bubble / resin balloon dispersion 1. Charged and mixed for about 2 minutes. The mixture was cast into an open mold within a usable life having fluidity, cured, and post-cured in an oven controlled at 110 ° C. ± 10 ° C. for 6 hours to produce a microcellular polyurethane foam. The surfactant used was 13.6 % by weight based on the total amount of the first component and the chain extender , and the resin balloon was 0.2 % by weight.
[0049]
The resulting microcellular polyurethane foam had uniform cells having a density of 0.75 g / cm ³ , a hardness (ASKER C) of 94, and an average cell diameter of 50 μm.
[0050]
(Example 2)
A microcellular polyurethane foam was prepared in the same manner as in Example 1 except that adiprene L-315 (NCO = 9.25% manufactured by Uniroyal) was used as the isocyanate-terminated prepolymer. The surfactant used was 13.6 % by weight based on the total amount of the first component and the chain extender , and the resin balloon was 0.2 % by weight.
[0051]
The obtained microcellular polyurethane foam had uniform cells having a density of 0.75 g / cm ³ , a hardness (ASKER C) of 95, and an average cell diameter of 40 μm.
[0052]
(Example 3)
A microcellular polyurethane foam was prepared in the same manner as in Example 1 except that adiprene LF-751D (NCO = 9.25% manufactured by Uniroyal) was used as the isocyanate-terminated prepolymer. The surfactant used was 13.6 % by weight based on the total amount of the first component and the chain extender , and the resin balloon was 0.2 % by weight.
[0053]
The resulting microcellular polyurethane foam had uniform cells having a density of 0.75 g / cm ³ , a hardness (ASKER C) of 97, and an average cell diameter of 40 μm.
[0054]
(Example 4)
A microcellular polyurethane foam was prepared in the same manner as in Example 1 except that the amount of EXPANCEL 551DE (manufactured by Nippon Philite) was changed to 0.9 g. The surfactant used was 13.6 % by weight based on the total amount of the first component and the chain extender , and the resin balloon was 0.6 % by weight.
[0055]
The resulting microcellular polyurethane foam had uniform cells with a density of 0.60 g / cm ³ , a hardness (ASKER C) of 94, and an average cell diameter of 50 μm.
[0056]
(Example 5)
A microcellular polyurethane foam was prepared in the same manner as in Example 1 except that the amount of the silicone foam stabilizer SH-192 was changed to 15 g. The surfactant used was 10.6 % by weight based on the total amount of the first component and the chain extender , and the resin balloon was 0.2 % by weight.

[0057]
The resulting microcellular polyurethane foam had uniform cells having a density of 0.75 g / cm ³ , a hardness (ASKER C) of 94, and an average cell diameter of 50 μm.

Claims (5)

To a first component containing an isocyanate prepolymer, a resin balloon and a silicon-based nonionic surfactant having no hydroxyl group are added so as to be 5 to 50% by weight in the fine cell polyurethane foam, and the first component is added . Stirring with the non-reactive gas to disperse the non-reactive gas as fine bubbles to form a bubble / resin balloon dispersion , and mixing and curing a chain extender having a molecular weight of 500 or less with the bubble / resin balloon dispersion. A method for producing a microcellular polyurethane foam, comprising: The method for producing a microcellular polyurethane foam according to claim 1, wherein the amount of the resin balloon added is 0.1 to 1.0% by weight based on the total amount of the first component and the chain extender . A microcellular polyurethane foam obtained by the production method according to claim 1. A polishing sheet comprising the microcellular polyurethane foam according to claim 3. The polishing sheet according to claim 4, wherein a groove is provided on the sheet surface.