JP2004189830A - Method for producing microporous resin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method suitable for producing a microporous resin foam with stable density, especially a microporous polyurethane foam, using a resin feedstock curable on reaction. <P>SOLUTION: The method for producing the microporous resin foam comprises the step of preparing a foam dispersion by using the resin feedstock curable on reaction, using an agitating apparatus equipped with an agitator and a mixing vessel, adding a surfactant to the resin feedstock, and agitating the resultant mixture in the presence of an inert gas, and the step of curing the foam dispersion under reaction into the objective microporous resin foam, wherein the 1st step involves carrying out a density adjustment by sensing the liquid level height using a liquid level detector equipped in the agitating apparatus. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

上記の結果より、本発明の製造方法によれば、樹脂原料であるイソシアネート基末端プレポリマーのロットが変動して溶融粘度が変動した場合でも、密度（比重）、硬度のバラツキの小さな微細気泡ポリウレタン発泡体が安定して得られることが分かる。
【図面の簡単な説明】
【図１】微細気泡ポリウレタン発泡体の製造に好適な撹拌装置を例示した概略側面図
【図２】撹拌容器内の撹拌翼の位置の例を示した上面図
【図３】撹拌容器に設けた測定窓を通して液面高さを検出する例を示した側面図
【符号の説明】
１０ 撹拌装置
２０ 撹拌機
３２ 液面検出装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a resin foam having uniform fine cells, particularly a resin foam having closed cells.
[0002]
[Prior art]
As a method for producing a reaction-curable resin foam, a foaming agent that decomposes upon heating to generate a gas such as nitrogen is mixed with a resin raw material, and the resin raw material composition is heated and foamed and simultaneously cured. A method for producing a foam, a method of mixing a foaming agent that does not itself undergo a chemical reaction but gasifies by heating with a resin raw material, heats and foams the resin raw material composition, and simultaneously cures the foam to produce a foam. Methods and the like are known.
[0003]
As the reaction curable resin constituting the foam, a polyurethane resin, a phenol resin, and an epoxy resin are usually most frequently used.
[0004]
As a specific example, as a method for producing a polyurethane foam, a method is known in which a foaming agent is added to components such as a polyol compound and an isocyanate compound which constitute a polyurethane polymer, and the mixture is foamed and cured. Water and low-boiling halogenated hydrocarbons are known as such blowing agents (for example, Non-Patent Document 1).
[0005]
As another method for producing a polyurethane foam, a surfactant is added to one of the components forming a polyurethane by the reaction of the two liquids, and the mixture is mechanically stirred to form a foam dispersion, and the foam dispersion is left in the foam dispersion. A technique is known in which the above reaction components are mixed to form a polyurethane foam. According to this production method, a polyurethane foam having a finer and more uniform cell diameter than when a foaming agent is used can be obtained (Patent Document 1).
[0006]
[Non-patent document 1]
Keiji Iwata, "Polyurethane Resin Handbook", Nikkan Kogyo Shimbun, September 25, 1987, p125
[Patent Document 1]
JP 2000-178374 A [Problems to be Solved by the Invention]
According to the manufacturing method using a foaming agent disclosed in Non-Patent Document 1, the density of the foam can be adjusted by the amount of the foaming agent to be added. When a foam is formed and foamed and cured in its molding space using a mold to produce a polyurethane foam molded product, the so-called packing ratio (foaming can be performed freely) together with the amount of the foaming agent. The density can also be adjusted by adjusting the ratio between the case and the volume of the mold cavity). However, the cell diameter of the obtained foam exceeded 100 μm, and it was not possible to produce a foam having fine cells.
[0007]
On the other hand, according to the production method described in Patent Document 1, it is possible to produce a foam of fine cells having a cell diameter of less than 100 μm, but it is difficult to adjust the foam density, and the properties of the resin raw material, particularly the viscosity, There is a problem that it is easily affected by variations. Although the foam density can be adjusted to some extent by adjusting the stirring time, the foam density cannot be adjusted accurately, and a foam having a stable foam density cannot be produced.
[0008]
An object of the present invention is to provide a method for producing a resin foam which can produce a microcellular resin foam having a stable density by using a resin material which reacts and cures. The method for producing a foam of the present invention is particularly suitable for a method for producing a microcellular polyurethane foam.
[0009]
[Means for Solving the Problems]
The present invention is a method for producing a fine cellular resin foam using a resin material that reacts and cures,
Using a stirrer with a stirrer and a mixing vessel,
Adding a surfactant to the resin raw material, stirring in the presence of an inert gas to produce a foam dispersion liquid, and curing the foam dispersion liquid into a fine foam by reacting and curing the foam dispersion liquid; Process
The bubble dispersion liquid production process is characterized in that the density is adjusted by detecting the liquid level with a liquid level detection device provided in a stirring device.
[0010]
With this configuration, it was possible to easily and easily produce a reaction-curable resin foam having fine cells having an average cell diameter of 100 μm or less, a small variation, and a stable density.
[0011]
That is, if the relationship between the amount of raw materials used, the liquid surface height of the foam dispersion obtained by mechanical stirring, and the density of the obtained foam is measured in advance according to the stirring vessel used, the amount of raw materials used can be specified. Then, by detecting the liquid surface height of the cell dispersion liquid, it is possible to easily produce a foam having a desired density and to reduce the variation in the density.
[0012]
In the above-mentioned invention, the size of the bubbles can be adjusted together by appropriately selecting the rotation speed and shape of the stirring blade in the stirrer, the type of the surfactant, and the like.
[0013]
The curing method in the curing step includes a method of adding, mixing and curing a reactive component that forms a polymer by reacting with a component constituting the foam dispersion, a method of adding a polymerization catalyst, mixing and curing, an electron beam. For example, a method of curing by irradiating energy rays such as ultraviolet rays or ultraviolet rays can be used.
[0014]
In the method for producing a microcellular resin foam, the microcellular resin foam is a microcellular polyurethane foam,
The resin raw material comprises a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound,
Using an isocyanate group-containing prepolymer as the first component,
In the bubble dispersion liquid production step, a silicon-based nonionic surfactant having no hydroxyl group is added to the isocyanate group-containing prepolymer, and the mixture is stirred with a non-reactive gas by the stirring device to disperse the non-reactive gas as fine bubbles. And forming a cell dispersion 1 by mixing the cell dispersion 1 with the second component to form a curable cell dispersion. The curing step comprises: Is cured to obtain a fine cell polyurethane foam.
[0015]
Further, in the method for producing the fine cell foam, the fine cell resin foam is a fine cell polyurethane foam,
The resin raw material comprises a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound,
A polyol composition containing a polyol compound is used as the second component, and in the foam dispersion manufacturing step, a silicon-based nonionic surfactant is added to the polyol composition, and a non-reactive gas is stirred with the stirring device. And dispersing the non-reactive gas as fine bubbles to form a bubble dispersion liquid 2, comprising a mixing step of mixing the first component with the bubble dispersion liquid 2 to form a curable bubble dispersion liquid. In the curing step, the curable cell dispersion is preferably cured to form a fine cell polyurethane foam.
[0016]
With such a constitution, in any of the inventions, a surfactant is added to one of the components forming the polyurethane by the reaction of the two liquids and mechanically stirred to form a foam dispersion, and the remaining reaction components are added to the foam dispersion. In the production of a polyurethane foam obtained by mixing a polyurethane foam, it is possible to more precisely adjust the density of the obtained polyurethane foam.
[0017]
It is preferable that the liquid level detecting device is a liquid level detecting device that measures a liquid level by reflection of electromagnetic waves or ultrasonic waves.
[0018]
By using such a liquid level detecting device, it is possible to measure the liquid level without contact and with high accuracy. Examples of the electromagnetic wave include γ-ray, ultraviolet light, visible light, microwave, laser, and the like. A liquid level detection device that measures the liquid level by reflection of electromagnetic waves or ultrasonic waves generally includes a radiating section that emits electromagnetic waves or ultrasonic waves toward the measurement target and a reception section that receives reflection from the measurement target. Have been. When a resin raw material that reacts and cures with an energy beam is used, an energy beam that does not cause polymerization is used.
[0019]
The microcellular resin foam obtained by the production method of the present invention has a cell diameter of 20 to 100 μm and a density of 0.1 to 1.1 g / cm ³ , preferably 0.5 to 1.1 g / cm ³ .
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
As the resin material of the foam used in the present invention, the viscosity of the raw material before curing is relatively low, and a reaction-curable resin that entrains bubbles by mechanical stirring to form a bubble dispersion liquid can be used without particular limitation. The so-called thermosetting resin corresponds to this. Specifically, polyurethane resin, epoxy resin, phenol resin, acrylic resin, unsaturated polyester resin, polyimide resin and the like are exemplified.
[0021]
When a resin material that forms a hard resin, such as a phenol resin, an epoxy resin, a hard urethane resin, or a polyimide resin, is used, the resulting fine cell foam is also a hard, highly heat-resistant resin foam, and has an elasticity. When a raw material such as a resin having rubber elasticity, for example, a polyurethane resin having rubber elasticity is used, the obtained fine cell foam becomes an elastic foam. Further, the microcellular resin foam obtained by the production method of the present invention is a foam having a high closed cell ratio.
[0022]
For example, when a polyurethane resin is used as a raw material, a foam having a hardness of 60 to 95 at Shore A is preferable as various cushioning materials, and a foam having a hardness of 40 to 65 at Shore D is used in, for example, a semiconductor device manufacturing process. It can be suitably used as a polishing layer material or the like of a polishing pad in the above.
[0023]
Among the above-mentioned resin materials, it is preferable to use a polyurethane resin that can be arbitrarily manufactured by selecting a material from a soft foam having excellent elasticity to a foam having high hardness.
[0024]
Known polyurethane-forming raw materials can be used as the polyurethane foam raw material of the present invention. In the second aspect of the invention, the isocyanate group-terminated prepolymer is used as a cell dispersion forming material, and in the third aspect of the invention, the polyol composition is used as a cell dispersion forming material.
[0025]
The isocyanate group-terminated prepolymer (also referred to as an isocyanate prepolymer) is a polyisocyanate compound and a polyol compound having an equivalent ratio NCO / H ^* of isocyanate group (NCO) and active hydrogen group (H ^* ) of 1.6 to 2. 6, preferably an NCO-terminated oligomer produced by a heating reaction in the range of 1.8 to 2.2. The use of commercially available isocyanate prepolymers is also suitable.
[0026]
The polyol composition is a composition containing a polyol compound as a main component. As the polyol compound, in addition to a general polyol compound, a polyisocyanate compound and a polyol compound are heated at an H ^* / NCO equivalent ratio of 1.6 to 2.6, preferably 1.8 to 2.2. It is also possible to use an oligomer having an active hydrogen group terminal (also referred to as an OH prepolymer) produced by the reaction.
[0027]
As the polyurethane resin raw material, a compound known in the technical field of polyurethane can be used without limitation. Specifically, this is exemplified in Non-Patent Document 1.
[0028]
The active hydrogen group-containing compound is an organic compound having at least two or more active hydrogen atoms, and is a compound usually called a polyol compound or a chain extender in the technical field of polyurethane.
[0029]
Examples of the polyol compound include polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, polyester-polyether polyols, polymer polyols in which polymers such as acrylonitrile and styrene are vinyl-added or dispersed, urea-dispersed polyols, carbonates Polyols and the like can be used as the polyol of the present invention.
[0030]
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.
[0031]
As the non-reactive gas used to form the fine bubbles, a gas that does not react with the resin material can be used without any particular limitation. Specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, low-boiling hydrocarbons such as n-pentane and cyclopentane, HFC compounds, and mixtures thereof. In particular, use of air from which moisture has been removed by drying is most preferable in terms of cost.
[0032]
As the surfactant used in the present invention, a surfactant capable of forming a cell dispersion liquid of fine cells is selected according to each resin raw material. As the surfactant, a known surfactant, in particular, a commercially available surfactant is used. When polyurethane is used as the resin material, it is preferable to use a silicon-based nonionic surfactant. As the silicon-based nonionic surfactant, there is no limitation as to those which form fine bubbles stably when the above-mentioned first component, second component or a mixture thereof is stirred in the presence of a non-reactive gas. Can be used.
[0033]
In particular, a surfactant used as a foam stabilizer in the technical field of polyurethane is used because of its good compatibility with a polyol compound and an isocyanate prepolymer.
[0034]
When the isocyanate prepolymer is used as the foam dispersion 1, a surfactant having no active hydrogen group such as a hydroxyl group is used. Those having no active hydrogen group such as a hydroxyl group which reacts with an isocyanate group. Specifically, silicone foam stabilizers SH-190 and SH-192 (manufactured by Toray Dow Corning Silicon Co., Ltd.), L-5340 (Nihon Unicar Co., Ltd. )).
[0035]
The surfactant used when the polyol composition is used as the cell dispersion 2 may have a hydroxyl group or the like.
[0036]
The addition amount of the above-mentioned surfactant is appropriately set in consideration of the properties of the resin raw material and the surfactant to be used, the inert gas, and the like. It is preferably 0.5 to 10 parts by weight.
[0037]
Preferred examples of the device used in the present invention will be described with reference to the drawings.
FIG. 1 is a side view schematically showing a stirring device. The stirrer 10 has a stirrer 20 having a pair of stirring blades 14A and 14B driven and rotated by a motor 12, and a stirring vessel 16, and the stirrer 20 is controlled by an elevating device 24 provided on a column 18. Mounted up and down. FIG. 2 is a top view showing the arrangement of the stirring blades 14A and 14B arranged in the stirring vessel 16. Two stirring blades are provided orthogonal to the rotation axis, and the rotation blades 14A and 14B mounted on the two rotation shafts are configured to rotate in opposite directions (arrows) and not interfere with each other. ing.
[0038]
An arm 30 is provided on the column 18, and a liquid level detection device 32 is mounted on the arm 30.
[0039]
At the bottom of the stirring vessel 16, there is provided a valve 34 for discharging the foam dispersion or a curable foam dispersion obtained by mixing other components with the foam dispersion. In order to quickly discharge the curable foam dispersion liquid, it is a preferable embodiment that the stirring vessel is hermetically sealed and air pressurizable. In a preferred embodiment, the stirring container 16 is provided with a jacket or the like so that the temperature can be adjusted.
[0040]
Although the liquid level detecting device shown in FIG. 1 is installed at one place above the liquid level, it may be installed at two or more places, in which case, two or more liquid level detection signals are processed to process the liquid level. An arithmetic device for calculating the average value of the surface heights may be provided. Although the liquid level is undulated by the stirring, if the positional relationship between the installation position of the stirrer 20 and the installation position of the liquid level detection device 32 in the stirring vessel 16 is set to be constant, the liquid level is increased regardless of the presence of the undulation. By detecting the thickness, a foam having a predetermined density can be obtained.
[0041]
When a cylindrical container having a cylindrical upper portion as illustrated in FIG. 1 is used in combination with the stirring container 16, when the amount of the raw material used is determined, the liquid level and the foam density are fixed. It is also possible to produce foams of any density by selecting the liquid level to form the relationship.
[0042]
FIG. 3 shows an example in which a transparent measurement window 42 is provided on the side surface of the stirring container 16 and the liquid level detection device 40 measures the liquid level L from the side.
[0043]
In the present invention, a known stirring device can be used without particular limitation as a stirring device for forming a bubble dispersion of a resin raw material by converting non-reactive gas into fine bubbles, and specifically, a homogenizer, a Hobart, and the like. A mixer, a dissolver, a twin-screw planetary mixer (planetary mixer) and the like are exemplified. However, a stirrer that causes a strong temperature rise by stirring is not preferable because the temperature of the foam 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 as shown in FIG. 1 is preferable because fine bubbles can be obtained.
[0044]
In the present invention, in the case of performing agitation for preparing a cell dispersion, and mixing and adding the remaining components to form a curable cell dispersion, the latter-stage stirring is not particularly agitation for forming bubbles. It is preferable to use the same stirring device by adjusting the stirring conditions such as adjusting the rotation speed of the stirring blade so as not to entrap large bubbles.
[0045]
Conditions for producing the foam 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 equal to or higher than the melting point of the resin raw material, and the curing reaction is rapidly performed. It must be below the temperature at which it does not proceed.
[0046]
When producing a polyurethane foam, the temperature is preferably from 0 ° C to 140 ° C, more preferably from 10 to 120 ° C. 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 compound and the active hydrogen compound selected. If the temperature rise of the system due to the heat of reaction is large, the bubbles in the bubble 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, sufficient It is preferable to perform temperature control.
[0047]
In the method for producing a microcellular resin foam of the present invention, heating and post-curing the foam that has been reacted until the foam dispersion is poured into the mold and no longer flows is an effect of improving the physical properties of the foam. And 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.
[0048]
In the present invention, other components may be added in addition to the resin raw material. Specific examples include a fine resin hollow sphere, a filler such as a resin fine powder or a fine powder of an inorganic substance, a retarder for adjusting a curing reaction rate, a coloring agent such as a dye or a pigment, and a plasticizer. .
[0049]
【Example】
Hereinafter, examples showing the structure and effects of the present invention will be described based on an example of producing a polyurethane foam.
(Example)
Using a stirring device shown in FIG. 1, coronate C-6912 (Nippon Polyurethane) using polyether polyol as a raw material as an isocyanate prepolymer, and 4,4′-methylenebis (o-chloroaniline) (Ihara) as a second component Microcellular polyurethane foam was produced using Chemical Co., Ltd. (Cureamine MT). The stirrer was equipped with a laser displacement meter (Keyence) as a liquid level detector. The positional relationship between the stirring device, the stirring vessel, and the laser displacement meter is fixed.
To 100 parts by weight of Coronate C-6912, 5 parts by weight of a silicone surfactant SH-192 (Toray Dow Corning Silicon) was added, and the temperature was adjusted to 80 ° C. 25.2 kg (about 50 vol% of the volume of the stirring vessel) of the first component is placed in a stirring vessel, and stirred at a rotation speed of a stirring blade of 900 rpm. Detected by a displacement meter, the rotational speed of the stirring blade was reduced to 600 rpm, and adjusted to 120 ° C., and the molten second component was added so as to be 22.6 parts by weight based on 100 parts by weight of the isocyanate prepolymer. After stirring to form a curable foam dispersion, the mixture was poured into a rectangular mold. When the fluidity of the curable cell dispersion liquid in the mold was lost, it was placed in an oven at 120 ° C., heated for 5 hours, and post-cured to obtain a foam block.
[0050]
The experiment was repeated 10 times while keeping the amount of the raw material used and the liquid level detected by the laser displacement meter constant, and the specific gravity and the hardness of the obtained microcellular polyurethane foam were measured. The average cell diameter of the foam was 50 to 55 μm in all cases.
[0051]
The experiment was carried out using lots of three different NCO group concentrations and different viscosities of Coronate C-6912, and the effects of variations in viscosity were also examined.
[0052]
(Comparative example)
Three kinds of lots having different NCO group concentrations and different viscosities were used in the same manner as in the example except that the stirring time was fixed so that the foam density was 0.9. Was repeated ten times, and the density (specific gravity as data) and hardness variation of the obtained microcellular polyurethane foam were measured. Each of the obtained foams was fine bubbles having an average cell diameter of 50 to 55 μm.
[0053]
<Evaluation method>
(Measurement of foam specific gravity)
Specific gravity was measured instead of density according to JIS Z 8807-1976. A strip-shaped sample having a width of 4 cm and a length of 8.5 cm (arbitrary thickness) was cut out from the foam block, allowed to stand for 16 hours in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and then a hydrometer ( (Manufactured by Sartorius).
[0054]
(Hardness measurement method)
It measured based on JISK6253-1997. The sample cut out from the foam block was allowed to stand in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% for 16 hours, and then the Shore A hardness was measured using an Asker A hardness meter (Kobunshi Keiki Co., Ltd.). did.
[0055]
Table 1 shows the evaluation results.
[Table 1]

From the above results, according to the production method of the present invention, even when the lot of the isocyanate group-terminated prepolymer as the resin raw material fluctuates and the melt viscosity fluctuates, the fine cell polyurethane having a small variation in density (specific gravity) and hardness is obtained. It can be seen that the foam can be obtained stably.
[Brief description of the drawings]
FIG. 1 is a schematic side view illustrating a stirrer suitable for producing a microcellular polyurethane foam. FIG. 2 is a top view showing an example of positions of stirring blades in a stirring vessel. FIG. 3 is provided in a stirring vessel. Side view showing an example of detecting the liquid level through a measurement window.
10 stirrer 20 stirrer 32 liquid level detector

Claims (4)

A method for producing a fine cellular resin foam using a resin material that reacts and cures,
Using a stirrer with a stirrer and a mixing vessel,
Adding a surfactant to the resin raw material, stirring in the presence of an inert gas to produce a foam dispersion liquid, and curing the foam dispersion liquid into a fine foam by reacting and curing the foam dispersion liquid; Process
The method for producing a fine cellular resin foam, wherein in the step of producing a cell dispersion liquid, the density is adjusted by detecting the liquid level with a liquid level detector provided in a stirring device. The fine cell resin foam is a fine cell polyurethane foam,
The resin raw material comprises a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound,
Using an isocyanate group-containing prepolymer as the first component,
In the bubble dispersion liquid production step, a silicon-based nonionic surfactant having no hydroxyl group is added to the isocyanate group-containing prepolymer, and the mixture is stirred with a non-reactive gas by the stirring device to disperse the non-reactive gas as fine bubbles. And forming a cell dispersion 1 by mixing the cell dispersion 1 with the second component to form a curable cell dispersion. The curing step comprises: The method for producing a microcellular resin foam according to claim 1, wherein the resin is cured to obtain a microcellular polyurethane foam. The fine cell resin foam is a fine cell polyurethane foam,
The resin raw material comprises a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound,
Using a polyol composition containing a polyol compound as the second component,
The bubble dispersion manufacturing step includes adding a silicon-based nonionic surfactant to the polyol composition, stirring the non-reactive gas with the non-reactive gas by the stirring device, and dispersing the non-reactive gas as fine bubbles. A mixing step of mixing the first component with the bubble dispersion liquid to form a curable bubble dispersion liquid; and the curing step includes curing the curable bubble dispersion liquid to obtain fine particles. The method for producing a fine cellular resin foam according to claim 1, which is a cellular polyurethane foam. The method for producing a fine cellular resin foam according to any one of claims 1 to 3, wherein the liquid level detecting device is a liquid level detecting device that measures a liquid level by reflection of electromagnetic waves or ultrasonic waves.

Images