JP2006176550A - Polyorganosiloxane foam-forming material, method for producing the same, and foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam having a low shrinkage and other excellent properties. <P>SOLUTION: The polyorganosiloxane foam-forming material comprises 100 pts.wt. (A) specified addition-reaction-type polyorganosiloxane composition, 1 to 20 pts.wt. (B) polyoxyalkylene-based water-absorbing resin powder of a mean particle diameter of 1 to 500 μm, 0.1 to 5 pts.wt. (C) nonionic surfactant, 50 to 250 pts.wt. (D) water, and 1 to 50 wt.%, based on water (D), (E) filler having hydrophilic groups on the surface, wherein at least (E) is formulated after the specified polyorganosiloxane (A1) is uniformly mixed with reinforcing silica and/or carbon black (A4). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel polyorganosiloxane foam material, and more specifically, by heating and curing and dehydrating, a foam having an arbitrary shape can be easily formed without generating a high foaming pressure. The present invention relates to a polyorganosiloxane foam material obtained in the above; a production method thereof; and a foam obtained by molding from the foam material and a production method thereof. Furthermore, the present invention relates to a sponge roll formed of the foam, particularly a sponge roll used for a fixing portion of dry toner, and a conductive sponge roll for controlling the dry toner.

  Conventionally, polyorganosiloxane foams that cure to form foams have been known to have various foaming mechanisms, including methods that use organic foaming agents. There was a problem with each sex.

  In recent years, when a foam obtained from this type of polyorganosiloxane foam material is used for applications such as a fixing roll of OA equipment, it has been required to have a low compression set at a high temperature. Moreover, depending on the application, it is also required to increase the hardness of the foam without increasing the thermal conductivity of the foam.

In order to provide a polyorganosiloxane foaming material that satisfies such requirements, the applicant of the present application can easily and safely form a foam having uniform cells using a water-absorbing polymer and water. A siloxane foam material was proposed (Patent Documents 1 and 2).
JP 2002-114860 A JP 2003-226774 A

  The methods of Patent Documents 1 and 2 are those in which a water-absorbing resin that has absorbed water is blended in a liquid silicone rubber composition and cured, and then post-cured to evaporate water to obtain a foam. According to this method, it is possible to obtain a foam material that gives a foam having uniform bubbles and low compression set at high temperatures.

  However, after further research by the present inventors, the methods disclosed in Patent Documents 1 and 2 have a large shrinkage rate of the obtained foam, and there are cases where the foam as designed cannot be provided. found. When the cause was examined, if the amount of the water-absorbent resin and water was not completely controlled, the water that exudes from the water-absorbent resin and dispersed in the silicone rubber evaporates without forming cells during post-cure. It turns out that.

  When the shrinkage rate of the foam is large, the foam is distorted, and in order to obtain a foam of a predetermined size, a post-process such as polishing is necessary, which causes problems such as complicated processes and material loss due to the post-process. There is also a problem that a smooth surface cannot be obtained because the cell cross section is exposed on the surface of the molded product by a subsequent process such as polishing. Furthermore, if the shrinkage rate of the foam is large, wrinkles are generated due to shrinkage during roll processing and the like, and there is a problem that it cannot be integrally formed with other materials such as a plastic film.

  As a result of repeated investigations to solve the above problems and to provide a foam having a small shrinkage ratio and excellent other characteristics, the present inventors have filled a hydrophilic group on the surface together with a water absorbent resin and water. It has been found that a foam having a small shrinkage can be obtained by blending a specific amount of the agent by a predetermined process, and the present invention has been completed.

That is, the present invention
(A) (A1) General formula:
R ¹ _a R ² _b SiO _{(4- (a + b)) / 2} (I)
(Wherein R ¹ represents an alkenyl group; R ² may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; a represents an integer of 1 or 2, b represents an integer of 0 to 2, and a + b is an integer of 1 to 3). Organosiloxane;
(A2) General formula:
R ³ _c H _d SiO _{(4- (c + d)) / 2} (II)
Wherein R ³ may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; c represents an integer of 0 to 2 D represents an integer of 1 or 2, and c + d is an integer of 1 to 3), a polyorganohydrogensiloxane having at least 3 units in the molecule, and an alkenyl group of component (A) The amount of hydrogen atoms bonded to silicon atoms to 0.5 to 5 per one;
(A3) platinum compound, catalyst amount; and (A4) 100 parts by weight of an addition reaction type polyorganosiloxane composition containing reinforcing silica and / or carbon black;
(B) 1 to 20 parts by weight of a polyoxyalkylene water-absorbent resin powder having an average particle size of 1 to 500 μm;
(C) 0.1-5 parts by weight of a nonionic surfactant;
(D) 50 to 250 parts by weight of water; and (E) a filler having a hydrophilic group on the surface; (D) 1 to 50% by weight based on water.
Including
At least (E) is a polyorganosiloxane foam characterized by being blended after uniform mixing of (A1) and (A4).

  Component (A) used in the present invention includes (A1) alkenyl group-containing polyorganosiloxane, (A2) polyorganohydrogensiloxane, (A3) platinum compound, and (A4) reinforcing silica and / or carbon black, Depending on the purpose, (A5) a polyorganosiloxane that contains an inorganic hollow filler and cures by addition reaction.

The component (A1) used in the present invention has a general formula:
R ¹ _a R ² _b SiO _{(4- (a + b)) / 2} (I)
An alkenyl group-containing polyorganosiloxane having at least two units represented by the formula (wherein R ¹ , R ² , a and b are as described above). The component (A1) is a base polymer of the composition of the present invention, and the alkenyl group bonded to the silicon atom is crosslinked by a hydrosilylation reaction with a hydrogen atom bonded to the silicon atom in the component (A2). At the same time, it is a component that imparts strength to the foam in cooperation with other components.

  As the component (A1), there is no particular limitation on the molecular structure as long as it is a polyorganosiloxane having at least two units represented by the above formula (I) in the molecule, linear, cyclic, branched Those having a siloxane skeleton can be used, but they are either linear or linear and branched in terms of ease of synthesis and imparting excellent rubber elasticity and mechanical properties to the composition. The alkenyl group-containing polyorganosiloxane is preferably used in combination. In particular, in order to obtain a foam material that exhibits fluidity at normal temperature, is easy to handle, and is compatible with a molding method suitable for mass production such as injection molding, the foam material has an appropriate viscosity and is obtained by curing. Since the foam has excellent mechanical properties, the component (A1) is a liquid at room temperature having an average degree of polymerization of usually 30 to 3,000. The average degree of polymerization is preferably 50 to 2,000, and more preferably 200 to 1,000.

Examples of R ¹ include vinyl, allyl, butenyl and the like, and a vinyl group is preferable because synthesis is easy. R ² includes a linear or branched alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecyl; a cycloalkyl group such as cyclohexyl; 2-phenylethyl, 2 -Aralkyl groups such as phenylpropyl; aryl groups such as phenyl; and substituted monovalent hydrocarbon groups such as chloromethyl, 3,3,3-trifluoropropyl, chlorophenyl, etc. Is preferable, a methyl group is preferable. a and b are as described above, and a is preferably 1 because synthesis is easy.

Such a unit represented by the formula (I) may be present at either the molecular end or in the middle of the molecule, but at least in order to impart good mechanical properties to the foam obtained by curing. Some are preferably present at the molecular ends, for example in the form of R ¹ R ² ₂ SiO _1/2 units.

In the siloxane unit other than the unit represented by the formula (I) in the component (A1), the organic group bonded to the silicon atom may be the same as or different from each other, and is the same as those exemplified as R ² . Examples are monovalent substituted or unsubstituted hydrocarbon groups. As the organic group bonded to the silicon atom of the component (A1), it is preferable that 85 mol% or more is a methyl group, since R ¹ described above is easy to synthesize and handle, and substantially all More preferably, it is a methyl group.

The component (A2) used in the present invention has a general formula:
R ³ _c H _d SiO _{(4- (c + d)) / 2} (II)
(Wherein R ³ , c and d are as described above) are polyorganohydrogensiloxanes having at least three units in one molecule, and a hydrogen atom bonded to a silicon atom is (A ) It contributes as a cross-linking agent that performs an addition reaction with an alkenyl group in the component, that is, a hydrosilyl reaction.

The component (A2) is not particularly limited as long as it has at least three units having a hydrogen atom bonded directly to a silicon atom in one molecule, and the molecular structure is linear, cyclic. In addition, a material having a branched siloxane skeleton can be used, but a linear material is preferable from the viewpoint of easy synthesis, and in order to obtain a foam excellent in mechanical strength, at least one of the components (A2) As a part, it is preferable to use polyorganohydrogensiloxane composed of R ³ ₂ HSiO _1/2 units and SiO ₂ units.

R ³ may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond. Examples of such a group include methyl, ethyl, propyl, Linear or branched alkyl groups such as butyl, hexyl, octyl, decyl, dodecyl; cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl; and chloromethyl, 3,3,3-trifluoro Examples thereof include substituted monovalent hydrocarbon groups such as propyl and chlorophenyl, and a methyl group is preferable because of ease of synthesis. c and d are each as described above, and d is preferably 1 because synthesis is easy.

In the siloxane unit other than the unit represented by the formula (II) in the component (A2), the organic group bonded to the silicon atom may be the same or different, and examples thereof are the same as R ^3. From the viewpoint of ease of synthesis, a methyl group is preferable.

  The blending amount of the component (A2) is an amount such that 0.5 to 5 hydrogen atoms bonded to the silicon atom are present per one alkenyl group of the component (A1). If this value is less than 0.5, there are few crosslinks and the mechanical strength becomes weak, and if it exceeds 5, the change in physical properties after curing increases.

  The component (A3) used in the present invention cures the foamed material of the present invention by an addition reaction between an alkenyl group in the component (A1) and a hydrogen atom bonded to a silicon atom in the component (A2). It is a catalyst used for. As the component (A3), platinum compounds such as chloroplatinic acid, complexes obtained from alcohol and chloroplatinic acid, platinum olefin complexes, platinum ketone complexes, and platinum vinylsiloxane complexes can be used. This (A3) component is used in a necessary amount as a catalyst, and this amount is usually 0.1 to 1,000 ppm in terms of platinum atom, preferably (A1) component, The amount is 0.5 to 200 ppm. If it is less than 0.1 ppm, the catalyst concentration is low and curing is insufficient. Further, even if it exceeds 1,000 ppm, there is no further effect, and the component (A3) contains a noble metal and is generally expensive, which is not economically preferable.

  The component (A4) used in the present invention is reinforcing silica and / or carbon black for obtaining excellent mechanical properties while maintaining the heat insulating property of the foam.

Examples of reinforcing silica include dry silica such as fumed silica and arc silica; wet silica such as precipitated silica and silica aerogel; and hexamethyldisilazane, trimethylchlorosilane, dimethyldichlorosilane, trimethylmethoxysilane, and octamethyl. Examples thereof include hydrophobic silica treated with an organosilicon compound such as cyclotetrasiloxane, and salt-mist silica and silica obtained by hydrophobizing the same are preferred. For good reinforcing effect, reinforcing silica has a specific surface area of usually 50 m ² / g or more, preferably 100~700m ² / g, more preferably those 130~500m ² / g is used.

Carbon black is mainly used for the purpose of imparting electrical conductivity to the foam as well as mechanical strength. Examples thereof include acetylene black and ketjen black, and the specific surface area is usually 30 m ² / g or more, preferably 50 to 1,000 m. ² / g is used.

  These reinforcing silica and / or carbon black may be used alone or in combination of two or more.

  (A4) Although the compounding quantity of a component changes also with the intended use of a foam, it is 0.5-50 weight% normally with respect to (A1) component, and in order to make outstanding heat insulation and mechanical strength compatible. The amount is preferably 2 to 40% by weight, more preferably 5 to 30% by weight. In particular, when carbon black is used as the component (A4) for the purpose of imparting conductivity to the foam, the amount thereof is preferably 5 to 30% by weight with respect to the component (A1).

  The component (A5) used in the present invention is an inorganic hollow filler for increasing the hardness of the foam without increasing the apparent specific gravity and thermal conductivity of the foam. Examples of inorganic hollow fillers include silica balloons; glass balloons such as borosilicate glass balloons, aluminoborosilicate glass balloons; shirasu balloons; and aluminosilicate balloons such as silicate balloons such as perlite balloons, fly ash balloons, and the like; In addition, non-silicic acid balloons such as carbon balloons are exemplified, and those with an arbitrarily controlled average particle size and particle size distribution are industrially easy to obtain, have good compatibility with base polymers, and are excellent in molded products Glass balloons are preferred because they give high mechanical properties and are chemically stable, and there is no adverse effect on curability, the appearance of the resulting foam is excellent, and the color tone can be arbitrarily selected. A glass balloon is particularly preferred. Moreover, a carbon balloon is preferable when a foam requires electroconductivity.

  As the component (A5), those having an average particle diameter of 0.1 to 500 μm are usually used, and since they are easily available, the excellent appearance of the foam is maintained, and the mechanical strength is not lowered. The particle diameter is preferably 1.0 to 200 μm, more preferably 10 to 150 μm.

  As the component (A5), those having an apparent specific gravity of 0.01 to 0.8 at 23 ° C. are usually used, have mechanical strength to withstand stress during processing, and increase the apparent specific gravity of the foam. The apparent specific gravity of the component (A5) is preferably 0.05 to 0.5 because the hardness can be increased without any problem and the thermal conductivity of the foam is suppressed.

  The blending amount of the component (A5) can be easily blended, a foam having high hardness is obtained, and the strength of the foam is not reduced. preferable.

  As the component (A5), commercially available products may be used as they are, and silazanes such as hexamethyldisilazane; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris, in order to increase the affinity and adhesion to the base polymer. Carbon-functional silanes such as (2-methoxyethoxy) silane and 3-methacryloxypropyltrimethoxysilane; or those subjected to surface treatment with a partially hydrolyzed product thereof may be used. Further, in order to modify the surface, the surface of the hollow filler is provided with a different inorganic layer, for example, an oxide such as silicon dioxide, titanium oxide or aluminum oxide; a complex oxide such as talc; or magnesium carbonate, What formed the layer of carbonates like calcium carbonate can also be used.

  (A) In addition to the components (A1) to (A4) and the component (A5) blended as necessary, the acetylene alcohols such as, for example, acetylene alcohols, are added to the addition reaction type polyorganosiloxane composition. A reaction inhibitor for addition reaction such as 3-methyl-1-butyn-3-ol and 1-ethynyl-1-cyclohexanol can be blended.

  (A) The polyorganosiloxane composition is prepared by mixing the components (A1) to (A4) and the component (A5) and other components blended as necessary by a mixing means such as a kneader, a mixer, or a roll. Can be prepared. However, the composition (A) prepared in this way usually has poor storage stability at room temperature, so it is stored in a cool and dark place, or stored with the above reaction inhibitor. The (A) polyorganosiloxane composition thus prepared exhibits moderate fluidity in an uncured state, is easy to mold, and the foam obtained by heating has excellent mechanical strength. Therefore, the apparent viscosity at 23 ° C. is preferably 0.5 to 1,000 Pa · s, and more preferably 1 to 500 Pa · s.

  The component (B) used in the present invention is a polyoxyalkylene having a functional group containing an active hydrogen at its terminal, such as an isocyanate compound, a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid alkyl ester. It is a polyalkylene water-absorbent resin powder obtained by modification by reaction with a functional compound. When this water-absorbing resin powder is used, the tendency to form secondary agglomerates is much less than that of water-absorbing resin powders such as polyacrylic acid partial sodium salts which are generally known. Manufacturing time is reduced.

  The structural unit of polyoxyalkylene is composed of oxyethylene units, or is a mixture of oxyethylene units as a main component and oxypropylene units and / or oxybutylene units. Also, polyoxyethylene and polyoxypropylene can be used in combination. Polyoxyethylene is preferably used because of its high water absorption. Examples of the terminal functional group having active hydrogen include a hydroxyl group, a carboxyl group, and an amino group, and a hydroxyl group is preferable because it can be easily synthesized. Such polyoxyalkylene can be used for diol compounds such as ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, and tetramethylene glycol; or polyhydric alcohols having a valence of 3 or more such as glycerin, trimethylolpropane, and pentaerythritol. , Ethylene oxide alone, propylene oxide alone, or a mixture of ethylene oxide and propylene oxide and / or butylene oxide can be obtained by ring-opening addition.

  The isocyanate compounds used as modifiers of these polyoxyalkylenes include n-propyl isocyanate, n-butyl isocyanate, n-hexyl isocyanate, dodecyl isocyanate, cyclohexyl isocyanate, benzyl isocyanate and phenyl isocyanate. Monoisocyanate compounds such as: and hexamethylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, xylylene diisocyanate, 2,4-tolylene diene Polyols such as isocyanate, 2,6-tolylene diisocyanate, trimer of tolylene diisocyanate, polymethylene polyphenyl isocyanate, trimethylolpropane Examples of the polyisocyanate compounds such as urethane isocyanate compounds and polyisocyanate adducts obtained by reacting a diisocyanate compound in the number of moles corresponding to the number of active hydrogens of 4,4-diphenylmethane diisocyanate, hexa Methylene diisocyanate and 2,4-tolylene diisocyanate are preferred.

  Examples of the polyvalent carboxylic acid similarly used include carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, adipic acid, fumaric acid, malonic acid, maleic acid, sebacic acid, trimellitic acid, and pyromellitic acid. Moreover, those anhydrides or alkyl esters thereof can also be used. Examples of the alkyl ester include methyl ester, dimethyl ester, and diethyl ester. Dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, dimethyl sebacate and pyromellitic anhydride are preferred.

  For example, when a polyoxyalkylene having hydroxyl group functionality is modified with an isocyanate compound, for example, amines such as trimethylamine, triethanolamine, triethylenediamine; or dibutyltin diacetate, dibutyltin. An organotin compound such as dilaurate can be used as a catalyst and reacted at a temperature of 50 to 150 ° C. In this case, in order to lower the melting temperature of the resulting modified product, a compound having active hydrogen such as water, polyols, amines and carboxylic acids may be added. Moreover, when modifying | denaturing with polyhydric carboxylic acid or its derivative (s), it can be made to react at the temperature of 120-250 degreeC, for example.

  The polyoxyalkylene water-absorbing resin thus obtained is a solid having a weight average molecular weight of typically 10,000 or more, and is preferably crosslinked. For example, (1) a trifunctional or higher polyol is used as a starting material when synthesizing polyoxyalkylene, and a branching unit is introduced into the polyoxyalkylene. The above can be used by (3) a method such as irradiating the modified polyoxyalkylene with ultraviolet rays or electron beams.

  As an example of such a polyoxyalkylene type water-absorbing resin, Aqua Coke TWB-P (Sumitomo Seika Co., Ltd., trade name) can be mentioned.

  The polyoxyalkylene-based water-absorbing resin used as the component (B) is in the form of a powder, and the average particle size is finer, and the finer foam of the cell is obtained. Depending on the purpose, it is usually selected from 1 to 500 μm, preferably 5 to 200 μm, more preferably 10 to 150 μm. If the average particle diameter is less than 1 μm, poor dispersion tends to occur, and if it exceeds 500 μm, sufficient strength of the foam cannot be obtained.

  (B) The compounding quantity of a component is 1-20 weight part with respect to 100 weight part of (A) component, Preferably it is 2-15 weight part. If it is less than 1 part by weight, the amount of water absorption is small, and when a necessary amount of water is blended, the water separates and a good foam cannot be obtained. On the other hand, if the amount exceeds 20 parts by weight, not only the effect does not change, but also the coloration due to the decomposition product of the resin in the heating step is remarkable.

  Since the component (C) used in the present invention does not inhibit the catalytic activity of the component (A3), a nonionic surfactant is used, and (D) to help disperse water in the system described later, (D) Used by dispersing in component. As component (C), glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene / polyoxypropylene Examples include block copolymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers; and silicone surfactants such as polysiloxane / polyoxyethylene graft copolymers. More than one species may be used in combination. It is preferable that the surfactant used has an HLB value (when using two or more kinds in combination, the weight average HLB value) of 5 to 14.

  (C) The compounding quantity of a component is 0.1-5 weight part with respect to 100 weight part of (A) component, and 0.2-4 weight part is preferable. When the component (C) is not used or the amount of the component (C) is less than 1 part by weight, the effect of assisting the dispersion of the component (D) into the system is not sufficient, and when heated rapidly in the step of obtaining the foam, The foam is destroyed and a foam having uniform fine foam cannot be obtained, and if it exceeds 5 parts by weight, the mechanical strength of the foam is lowered.

  The component (D) is water, and either city water or pure water may be used. The component (D) is uniformly dispersed in the foamed material, is volatilized by heating during molding or after molding, and is blended to leave a homogeneously dispersed homogeneous cell. Hydrosilyl by the component (A3) It is not for generating hydrogen by reaction with the group. As the blending amount of the component (D) is higher, a higher foaming ratio is obtained, but it is selected from the range of 50 to 250 parts by weight with respect to 100 parts by weight of the component (A), and the balance between the foaming ratio and the mechanical strength, 70 to 200 parts by weight are preferred. If it is less than 50 parts by weight, a predetermined thermal conductivity cannot be obtained and a satisfactory foam may not be obtained. If it exceeds 250 parts by weight, it may be difficult to disperse the component (A), and the mechanical strength will decrease.

The component (E) is a filler having a hydrophilic group on the surface, and plays a role of capturing and adsorbing water that has exuded from the water-absorbent resin and dispersed in the silicone rubber. As the filler having a hydrophilic group on the surface, fumed silica having silanol groups on the surface, dry silica such as arc silica; wet silica such as precipitated silica and silica airgel is used. In order to obtain an excellent trapping / adsorption effect, those having a specific surface area of 50 m ² / g or more are preferable.

  (E) The compounding quantity of a component is 1 to 50 weight% with respect to (D) water. If it is less than 1% by weight, there is almost no effect of capturing and adsorbing water, and if it exceeds 50% by weight, the viscosity of the compound becomes high and handling becomes difficult, and a flexible foam cannot be obtained.

  In the polyorganosiloxane foam material of the present invention, as long as the object of the present invention is not impaired, a polyorganosiloxane that does not correspond to the component (A1) or (A2), for example, a triorgano is used as a diluent. A polyorganosiloxane blocked with a silyl group or silanol group can be blended. If necessary, a flame retardant such as titanium dioxide, zinc carbonate, or manganese carbonate; a heat resistance improver such as iron oxide, iron oxide ferrite, or cerium hydroxide can be blended.

  The foam material of the present invention can be prepared by various procedures. However, in order to always obtain a stable bubble size, it is preferable to prepare as follows. That is, after (B) polyoxyalkylene water-absorbent resin powder is uniformly dispersed in (A) polyorganosiloxane composition in advance, (C) nonionic surfactant and (D) water are added to uniformly After being dispersed and uniformly dispersed as a whole, a foaming material can be obtained by mixing a filler having a hydrophilic group on the surface (E).

  As another method, (B) the polyoxyalkylene water-absorbing resin powder and (D) water are mixed, and (B) the polyoxyalkylene water-absorbing resin powder sufficiently absorbs water. Or (B) a polyoxyalkylene water-absorbent resin powder and (D) water, and (B) a polyoxyalkylene water-absorbent resin powder, or (B) a polyorganosiloxane composition and (C) a nonionic surfactant. (C) A nonionic surfactant is mixed, (B) a polyoxyalkylene water-absorbing resin powder sufficiently absorbs water, (E) a mixture in which a filler having a hydrophilic group is added to the surface, and (A) poly It can be obtained by a method of mixing with an organosiloxane composition.

  In addition, if (A2) is removed from (A2) instead of (A), a mixture is prepared using (A '), and (A2) and (A3) are added immediately before curing to preserve storage stability. Can be improved.

  The foam of the present invention is produced by curing and foaming by a production method including a step of molding the foam material of the present invention. As the molding, any method can be selected according to the properties of the foamed material and the shape of the object, such as injection molding, transfer molding, press molding, and molding such as casting. As a molding method, injection molding is preferable because mass production is easy.

  Molding is performed at room temperature or slightly heated, partially foamed to the extent that the foam becomes solid, or completely cured, and then dehydrated by the heating process, generating bubbles inside the solid. In addition, when only partial crosslinking is performed during molding, the crosslinking may be further advanced to complete the curing. Since the water-absorbing resin is decomposed by this heating, water is not absorbed again in the subsequent use stage. The molding temperature in the mold molding step can usually be arbitrarily selected in the range of room temperature to 200 ° C., preferably 60 to 100 ° C., depending on the type and amount of the component (A3). The heating temperature of a heating process can be arbitrarily set normally in the range of 100-350 degreeC, Preferably it is 150-300 degreeC.

  The advantage of such a two-stage method is that a more uniform foam can be obtained by separately setting the molding conditions and the foaming conditions.

When the foam is formed on a metal surface, for example, in a form bonded to a metal core, such as when the foam material of the present invention is used in the production of a sponge roll, a primer is applied to the metal surface in advance, as described above. Foaming material can be applied, filled or injected to form, cure and foam. When the roll requires heat resistance like a fixing roll, it is preferable to add a heat resistance improver such as iron sesquioxide to the foamed material. If necessary, particularly when used as a pressure roll in a fixing portion of a dry toner, a resin layer such as a fluororesin layer or a fluororubber layer is provided on the surface of the obtained roll as an outermost layer through an adhesive layer. Alternatively, it is preferable to provide a rubber layer. When the roll is a conductive roll, carbon black is used as the component (A4), and if necessary, a carbon balloon is used as the component (A5), and the volume resistivity of the foam is 10 ¹ to 10 ¹⁰ Ω. -Conductive rolls in the cm range can be obtained. These rolls may polish the surface or may be used as they are. Furthermore, when this conductive sponge roll is used for an application in contact with a photosensitive drum, in order to prevent contamination due to transfer of low molecular weight siloxane to a photosensitive drum, a film other than silicone, that is, a film other than silicone, It is preferable to form a rubbery film such as NBR or a resinous film such as a fluororesin.

  Hereinafter, the present invention will be further described by examples and comparative examples. In these examples, all parts represent parts by weight, and the viscosity and specific gravity represent values at 23 ° C. In addition, this invention is not limited by these Examples.

In the examples and comparative examples of the present invention, chain polysiloxanes having the following siloxane units and viscosities were used as the components (A1) and (A2).
a-1: polydiorganosiloxane having both ends blocked with dimethylvinyl groups and intermediate units consisting of dimethylsiloxane units, viscosity 10 Pa · s;
h-1: polymethylhydrogensiloxane having both ends blocked with trimethylsilyl groups, containing dimethylsiloxane units and methylhydrogensiloxane units as intermediate units, and 0.8% by weight of hydrogen atoms bonded to silicon atoms, viscosity 0.5 Pa · s;
As the component (A3), the following platinum compound was used.
p-1: Complex obtained from chloroplatinic acid and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, platinum atom content 2% by weight.

As the component (A4), the following fillers were used.
f-1: fumed silica surface-treated with hexamethyldisilazane;
As the component (B), the following water absorbent resin powder was used.
b-1: Isocyanate-modified polyoxyethylene water-absorbent resin powder from which particles having an average particle size of 40 μm and a particle size of 75 μm or more have been removed.

As the component (C), the following surfactant was used.
c-1: Polyoxyethylene lauryl ether (HLB: 9.6).

As the component (E), the following fillers were used.
e-1: precipitated silica not subjected to surface treatment.
e′-1: Precipitated silica surface-treated with hexamethyldisilazane.
[Examples 1-2, Comparative Examples 1-3]
A foam material was prepared by the composition (unit: part) shown in Table 1 and the production method shown in Table 1. Specifically, it is as follows.
Example 1 (Production method A)
(1) Both ends vinyl oil (a-1) and surface-treated fumed silica (f-1) are mixed under heating and reduced pressure, and after cooling, water-absorbing resin powder (b-1) is mixed, and water is further added. A mixture 1 obtained by mixing the surfactant and the surfactant (c-1) was obtained.
(2) Precipitated silica (e-1) was mixed with the mixture 1, H oil (h-1) and a platinum catalyst (p-1) were added to prepare a foam material.
Example 2 (Production method B)
(1) Both end vinyl oils (a-1) and surface-treated fumed silica (f-1) were mixed under heating and reduced pressure to obtain a mixture 1.
(2) The water-absorbent resin powder (b-1) is mixed with the mixture of water and surfactant (c-1), and the precipitated silica (e-1 ) To obtain a mixture 2.
(3) The mixture 1 and the mixture 2 were mixed, H oil (h-1) and a platinum catalyst (p-1) were added, and the foaming material was prepared.
Comparative Example 1 (Production Method A)
A foam material was prepared in the same manner as in Example 1 (Production method A) except that the precipitated silica (e-1) was not used.
Comparative Example 2 (Production Method A)
A foam was prepared in the same manner as in Example 1 (Production method A) except that precipitated silica (e′-1) surface-treated with hexamethyldisilazane was used instead of precipitated silica (e-1). .
Comparative Example 3 (Production Method C)
(1) Both ends vinyl oil (a-1), surface-treated fumed silica (f-1) and precipitated silica (e-1) are mixed under heating and reduced pressure, and after cooling, water absorbent resin powder (b -1) was mixed and the mixture 1 was obtained.
(2) Water and the surfactant (c-1) were mixed to obtain a mixture 2.
(3) The mixture 1 and the mixture 2 were mixed, H oil (h-1) and a platinum catalyst (p-1) were added, and the foaming material was prepared.
[Sheet forming method]
The foamed material prepared as described above is poured into a 120 mm × 120 mm, 6 mm thick mold, hermetically sealed, pressurized, press-molded by heating at 90 ° C. for 20 minutes, and a rubber-like elastic body is obtained. Obtained. The mold was opened, the elastic body was taken out, and heated in a dryer at 250 ° C. for 4 hours to remove moisture and produce a foam cured in a sponge shape.
[Roller molding method]
In a pipe-shaped mold having an inner diameter of 25 mm and a length of 230 mm, a shaft with an outer diameter of 12 mm whose surface was subjected to primer treatment was disposed via flanges at both ends so as to be the center of the pipe. The flanges at both ends have φ4mm holes as material casting holes and air vents.

  A fluororesin tube with a thickness of 50μ and an outer diameter of φ24.5mm with the inner surface etched and a primer applied is placed along the inner surface of the mold, and the mold tube, flange, shaft, and fluorine film are set on the lower side. Cast the mixed material from the casting hole of the flange (until the material overflows from the air vent of the upper flange), close the casting hole and air vent, cure in an oven at 90 ° C for 1 hour, and then reach room temperature The roll formed by cooling with water is taken out. The removed roll was placed in an oven at 250 ° C. and heated for 4 hours.

The following evaluation was performed about the foam sheet and roll obtained by the Example and the comparative example.
(1) Hardness: The hardness of the center portion and the portion 2 cm from the end (hereinafter referred to as the end portion) of the cured sheet was measured with a type E durometer in JIS K 6249.
(2) Linear shrinkage rate:
According to the sheet method of JIS K 6249, the distance between the centers of the opposite sides of the sheet was measured, and the linear shrinkage rate was calculated. (3) Thermal conductivity:
Measurement was performed using a rapid thermal conductivity meter manufactured by Kyoto Electronics Co., Ltd.
(4) Roll formability:
The forming state of the roll after forming was visually confirmed.
(5) Roll diameter:
The average value was obtained by measuring the diameter of a 2 cm portion from the center and end of the roller using a laser measuring machine.

  These results are shown in Table 1.

Claims (22)

(A) (A1) General formula:
R ¹ _a R ² _b SiO _{(4- (a + b)) / 2} (I)
(Wherein R ¹ represents an alkenyl group; R ² may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; a represents an integer of 1 or 2, b represents an integer of 0 to 2, and a + b is an integer of 1 to 3). Organosiloxane;
(A2) General formula:
R ³ _c H _d SiO _{(4- (c + d)) / 2} (II)
Wherein R ³ may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; c represents an integer of 0 to 2 D represents an integer of 1 or 2, and c + d is an integer of 1 to 3), a polyorganohydrogensiloxane having at least 3 units in the molecule, and an alkenyl group of component (A) The amount of hydrogen atoms bonded to silicon atoms to 0.5 to 5 per one;
(A3) platinum compound, catalyst amount; and (A4) 100 parts by weight of an addition reaction type polyorganosiloxane composition containing reinforcing silica and / or carbon black;
(B) 1 to 20 parts by weight of a polyoxyalkylene water-absorbent resin powder having an average particle size of 1 to 500 μm;
(C) 0.1-5 parts by weight of a nonionic surfactant;
(D) 50 to 250 parts by weight of water; and (E) a filler having a hydrophilic group on the surface; (D) 1 to 50% by weight based on water.
Including
A polyorganosiloxane foaming material, wherein at least (E) is blended after uniform mixing of (A1) and (A4). The foaming material according to claim 1, wherein the apparent viscosity at 23 ° C. of (A) is 0.5 to 1,000 Pa · s. The foamed material according to claim 1 or 2, wherein the average degree of polymerization of (A1) is 50 to 2,000. The foam material of any one of Claims 1-3 whose quantity of (A4) is 0.5 to 50 weight% of (A1). The polyorganosiloxane foam material according to any one of claims 1 to 4, wherein (A) further comprises (A5) an inorganic hollow filler. The polyorganosiloxane foam material according to claim 5, wherein (A5) is a borosilicate glass balloon. The polyorganosiloxane foam material according to claim 5 or 6, wherein the apparent specific gravity of (A5) is 0.01 to 0.8. The polyorganosiloxane foam material according to any one of claims 5 to 7, wherein an average particle diameter of (A5) is 0.1 to 500 µm. The polyorganosiloxane foam material according to any one of claims 5 to 8, wherein the amount of (A5) is 0.5 to 10% by weight of (A1). The foaming material according to any one of claims 1 to 9, wherein (B) is a polymer obtained by a reaction between a terminal reactive polyoxyalkylene and a polyisocyanate. (B) Polyoxyalkylene water-absorbing resin powder and (C) nonionic surfactant mixed in advance (D) water are mixed, and (B) polyoxyalkylene water-absorbing resin powder sufficiently absorbs water (E The foam material according to any one of claims 1 to 10, wherein a filler having a hydrophilic group on the surface is mixed, and (A) an addition reaction type polyorganosiloxane composition is blended therein. how to. (B) Polyoxyalkylene water-absorbent resin powder and (D) water are mixed in advance, (B) Polyoxyalkylene water-absorbent resin powder absorbs water sufficiently, and (E) A filler having a hydrophilic group on the surface is mixed. The foamed material according to any one of claims 1 to 10, wherein (A) an addition reaction type polyorganosiloxane composition and (C) a nonionic surfactant are blended therein. Method.
(A) In the addition reaction type polyorganosiloxane composition, (B) polyoxyalkylene-based water-absorbing resin powder is dispersed, and (C) a nonionic surfactant and (D) water are blended therein. The method for producing a foam material according to any one of claims 1 to 10, wherein a filler having a hydrophilic group on the surface is blended. A foam obtained by molding and curing the foam material according to any one of claims 1 to 10, and then evaporating water by heating. The foam according to claim 14, wherein the foam is obtained by the production method according to claim 11. The foam according to claim 14 or 15, which is a polishing-less sponge roll. The polishing-less sponge roll according to claim 16, wherein the surface is coated with a fluororesin. The polishing-less sponge roll according to claim 16, wherein the fluororesin film is integrally formed. A pressure roll used for a fixing part of dry toner, wherein a fluororubber layer or a fluororesin layer is provided as an outer layer of the polishingless sponge roll according to claim 16. The sponge roll according to claim 15, which contains carbon black and is used as a charging roll, a transfer roll, a developing roll or an electrostatic removal roll in contact with a photosensitive drum. A foam production method according to any one of claims 1 to 10, wherein the foam material is molded and cured at a temperature of 60 to 100 ° C, and then heated to a temperature of 150 to 300 ° C. The manufacturing method according to claim 20, wherein the molding is injection molding.