JP5948466B2 - Polyurethane foam and sealing material using the same - Google Patents

Description

  The present invention relates to a toner seal material, and more particularly to a toner seal material used for preventing toner leakage in an image forming apparatus such as a copying machine or a printer.

  With recent advances in electrophotographic technology, in an image forming apparatus such as a dry electrophotographic apparatus, a member using polyurethane foam is used as a member for various purposes such as charging, development, transfer, toner supply, and cleaning. Attention has been paid. Such a member using polyurethane foam is used in the form of a member for an image forming apparatus having elasticity such as a charging roller, a developing roller, a transfer roller, a toner supply roller, and a cleaning roller.

  In addition to the above roller member, as an internal member of an image forming apparatus using polyurethane foam having excellent sealing properties, it can be attached to the periphery of a toner containing portion, an image forming body, etc. There is a toner sealing material that functions to prevent leakage and diffusion of toner. A polyurethane foam used for a toner seal material is required to have a low air permeability and a fine cell structure.

  In a developing section of an image forming apparatus, generally, an electrostatic latent image is formed by attaching an image forming body such as a photoconductor that holds an electrostatic latent image and a toner abutting on the image forming body to be carried on the surface. A developing roller that forms a visible image and a toner supply roller that supplies toner to the developing roller are provided. In the developing unit, image formation is performed by a series of processes for conveying toner from the toner storage unit to the image forming body via the toner supply roller and the developing roller.

  On the other hand, a polyurethane foam generally contains a polyol, an isocyanate and a catalyst, and a foam stabilizer is used to prepare foamed cells during foaming. Examples of the foam stabilizer include water-soluble polyether siloxane from polydimethylsiloxane and ethylene oxide / propylene oxide copolymer, sodium salt of sulfonated ricinoleic acid, and a mixture of these with a polysiloxane / polyoxyalkylene copolymer. .

  As the catalyst, an organometallic catalyst and a tertiary amine catalyst have been generally used, and among them, a tertiary amine catalyst is known as an excellent catalyst for producing polyurethane. Among these tertiary amine catalysts, industrially utilized polyurethane catalysts include triethylenediamine, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, N, N, N ′, N'-tetramethylhexamethylenediamine, N-methyl-N '-(2-dimethylaminoethyl) piperazine, triethylamine, N-methylmorpholine, N-ethylmorpholine and the like can be mentioned. Of these, relatively low molecular weight and highly volatile catalysts, such as N-methylmorpholine, N-ethylmorpholine, triethylamine, etc., may have an important effect that greatly affects the cure rate and foam physical properties of polyurethane. Known and widely used.

  As a technique relating to a member for an image forming apparatus using a polyurethane foam, for example, in Patent Document 1, as a technique for preventing transpiration or migration of an amine catalyst or silicone, (A) a polyol has a mass average molecular weight of 2000 to 10,000. And (B) polyisocyanate contains at least one of diphenylmethane diisocyanate or a derivative thereof, and (C) a catalyst is a polyisocyanate. There is disclosed a member for an image forming apparatus comprising a polyurethane foam containing at least one reactive amine catalyst having at least one OH group or amino group capable of reacting with.

  Patent Document 2 discloses a mass containing a polyether polyol having 5% by mass or more of ethylene oxide as a terminal, as a technique for obtaining a polymer member for an image forming apparatus that is less contaminated with other members and hardly deteriorates. A reaction between a polyol (A) having an average molecular weight of 2,000 or more and 10,000 or less, a polyisocyanate (B) containing at least one kind of diphenylmethane diisocyanate or a derivative thereof, a blowing agent, and an amine catalyst (C) having a boiling point of 130 ° C. or less. In order to obtain a polyurethane foam, a production method is disclosed in which the polyurethane foam is dried at a temperature not lower than the boiling point of the amine catalyst (C) and not higher than 140 ° C. Furthermore, Patent Document 3 discloses a water-resistant polyurethane foam obtained by foaming a polyurethane foam raw material containing a polyol mainly composed of dimer acid polyol and an isocyanate mainly composed of diphenylmethane diisocyanate as a technology related to polyurethane foams having different uses. Is disclosed.

JP 2006-145594 A (Claims etc.) JP 2007-182497 A (claims, etc.) JP 2009-173806 A (Claims etc.)

  However, when a polyurethane foam containing a silicone foam stabilizer is used as a member for an image forming apparatus, low molecular weight silicone vaporizes and adheres to contacts inside the apparatus, resulting in a decrease in conductivity, and reading / writing on hard disks and the like. There was a problem that caused an error. In addition, the silicone foam stabilizer contained in the polyurethane foam may be transferred to another member such as a roller that contacts in the apparatus, and further transferred to an image, causing problems such as discoloration. For these problems, it is conceivable to use a silicone foam stabilizer having a reactive group. However, when a reactive silicone is used, there is a problem that foaming of the polyurethane foam raw material becomes difficult.

  As for the amine catalyst, the remaining amine catalyst may ooze out from the polyurethane foam of the member, and the contacted member may be discolored or deteriorated. Further, the volatile amine catalyst is vaporized from the member. However, it has various problems such as formation of a salt with an acid component in the atmosphere, causing a problem at a site where the acid component is attached.

  As disclosed in Patent Documents 1 and 2 above, various studies have been made on the blending of polyurethane foam for roller members such as toner supply rollers. However, the polyurethane foam blending used in the toner sealant has not been sufficiently studied so far, and the occurrence of problems due to blending components can be suppressed while ensuring the required performance as a sealant. It has been desired to realize a polyurethane foam formulation for a sealing material.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, have a good toner sealing performance, and do not cause defects or malfunctions due to adhesion or migration of a silicone foam stabilizer or an amine catalyst in a polyurethane foam formulation. To provide materials.

  As a result of intensive studies, the present inventors have found that the above-described problems can be solved by adopting the following configuration, and have completed the present invention.

That is, the present invention is a polyurethane foam obtained by foaming a polyurethane foam raw material containing a polyol, an isocyanate, a catalyst and a foam stabilizer.
The polyol is a dimer acid polyol, the ratio of diphenylmethane diisocyanate in the isocyanate is 55 to 75% by mass, the catalyst is a reactive amine, and the polyurethane foam raw material is 100 parts by mass of the polyol. The reactive amine is contained at 0.2 to 0.5 parts by mass, the foam stabilizer is contained at 3 to 5 parts by mass, and the crosslinking agent is contained at 1 to 3 parts by mass. It is. In the present invention, the ratio of diphenylmethane diisocyanate in the isocyanate is preferably 65 to 70% by mass, and the air permeability of the polyurethane foam is 5 cc / cm ² / sec. The number of cells is preferably 65 / inch or more.

  According to the present invention, because of the above-described configuration, the toner seal material has good toner sealing performance and does not cause defects or defects due to adhesion or migration of a silicone foam stabilizer or an amine catalyst in the polyurethane foam compounding. It became possible to realize.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The toner sealing material of the present invention is used for preventing leakage of toner in an image forming apparatus, and is formed by foaming a polyurethane foam raw material containing a polyol, an isocyanate, a catalyst, and a foam stabilizer. .

In the toner seal material of the present invention, dimer acid polyol (dimer acid polyester polyol) is used as the polyol among the components of the polyurethane foam raw material. The dimer acid is a dibasic acid, and the molecular weight obtained by dividing two monobasic fatty chains (usually 18 carbon atoms) into two by a carbon-carbon covalent bond is doubled. Refers to a dibasic acid. Typical examples of the compound include those represented by the following structural formula obtained by heating linoleic acid and oleic acid.

  The dimer acid polyol is a reaction product of the dimer acid and a short-chain diol, triol or polyol, a dimer acid polyester; a reaction product of a dimer acid and a polyalkylene glycol, polyalkylene triol or a long-chain polyol; A reaction product obtained by reacting dimer acid with other polycarboxylic acid, for example, adipic acid, and the above-mentioned various diols, triols or polyols; a reaction product of dimer acid and alkylene oxide or a mixture thereof. Although it is mentioned, it is not limited to this.

  The number average molecular weight of the dimer acid polyol is preferably 1000 to 10,000, and the hydroxyl value thereof is preferably 11.2 to 180 mg-KOH / g. These dimer acid polyols may be used alone or in combination of two or more.

  In the present invention, polyols such as polyether polyols, polyester polyols, and polyester polyether polyols other than the above-mentioned dimer acid polyols may be used in combination. In this case, the effect of the present invention by using dimer acid polyols Is effectively 80% by mass or more, particularly 90% by mass or more, more preferably 95% by mass or more, and most preferably only dimer acid polyol. Use.

  Moreover, in this invention, it is necessary to use diphenylmethane diisocyanate (MDI) as an isocyanate among the structural components of the said polyurethane foam raw material. The ratio of MDI in the isocyanate is required to be 55 to 75% by mass, and preferably 65 to 70% by mass. If the MDI ratio is too small, the foamed cells will not be sufficiently refined. If the MDI ratio is too large, the resulting polyurethane foam will be insufficiently stretched, and in either case, the required performance as a toner seal material cannot be satisfied. It will be a thing.

  The MDI is not particularly limited, and can be used regardless of the molecular weight distribution. For example, pure MDI (4,4'-MDI), polymeric MDI, crude MDI, etc. It can be used suitably. Examples of the isocyanate that can be used in combination with MDI include tolylene diisocyanate (TDI), and it is particularly preferable to use MDI and TDI in combination.

  In the toner seal material of the present invention, since the dimer acid polyol is used as the polyol and the ratio of MDI in the isocyanate is 55 to 75% by mass, the cell diameter of the obtained polyurethane foam can be made fine. Good sealing performance can be secured.

  Furthermore, in the present invention, among the constituent components of the polyurethane foam raw material, the catalyst contains a reactive amine, and the compounding amount of the reactive amine is 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the polyol. , Preferably, it is necessary to set it as 0.25-0.40 mass part. Since reactive amines react with isocyanates, the use of reactive amines as catalysts makes it difficult for amine catalysts to vaporize, bleed out, scatter, etc. even under wet heat conditions, etc. Since the occurrence of defects can be prevented, the printing performance can be improved. On the other hand, if a reactive amine is used, foaming of polyurethane becomes difficult and affects various physical properties such as compression residual strain of the resulting polyurethane foam, so the blending amount must be within the above range. If the amount of the reactive amine is too small or too large, the foamability of the polyurethane foam raw material deteriorates, and a polyurethane foam cannot be obtained substantially.

  Any reactive amine may be used as long as it has a functional group capable of reacting with an isocyanate group, and an amine compound having at least one hydroxyl group is preferably used. Examples of such amine compounds include N, N-dimethylaminoethoxyethanol (manufactured by Kao Corporation, trade name: Kao Riser No. 23NP), N, N-dimethylaminohexanol (manufactured by Kao Corporation, Product name: Cao Raiser No. 25), N, N-dimethylaminoethoxyethanol (DMAEE, manufactured by Kao Corporation, product name: Cao Raiser No. 26), monoethanolamine, diethanolamine, triethanolamine, dimethylaminoethanol (DMEA), N, N, N′-trimethylaminoethylethanolamine (TMAEEA), N-methyl-N ′-(2-hydroxyethyl) -piperazine (MHEP), N- (2-hydroxyethyl) morpholine (HEMO) And the like. These reactive amines may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the present invention, a catalyst other than the reactive amine may be used in combination. Examples of the catalyst that can be used in combination include an organometallic catalyst such as a tin catalyst, and the blending amount thereof can be 0.08 to 0.12 parts by mass with respect to 100 parts by mass of the polyol.

  Furthermore, in the present invention, among the constituents of the polyurethane foam raw material, the blending amount of the foam stabilizer is 3 to 5 parts by mass, preferably 3.5 to 4.5 parts by mass with respect to 100 parts by mass of the polyol. Is necessary. By making the blend of the foam stabilizer within the above range, it is possible to prevent the occurrence of problems due to the adhesion or migration of conventional silicone and improve the printing performance, while ensuring the foamability of the polyurethane foam raw material, and to achieve the desired A processable polyurethane foam having continuous cells can be obtained. If the blending amount of the foam stabilizer is too small or too large, the foamability of the polyurethane foam raw material deteriorates, and a polyurethane foam cannot be obtained substantially. As the foam stabilizer, a general-purpose silicone foam stabilizer can be used, and is not particularly limited. In particular, a silicone foam stabilizer having a low siloxane content is suitable.

  As a constituent component of the polyurethane foam raw material according to the present invention, in addition to the polyol, isocyanate, catalyst and foam stabilizer, it is preferable to contain a crosslinking agent in an amount of 1 to 3 parts by mass with respect to 100 parts by mass of the polyol. By blending the cross-linking agent in the above blending range, it is possible to appropriately control the air permeability of the obtained polyurethane foam in a very low region in combination with the optimization of the mixing ratio of the MDI. It becomes possible to improve further. As such a crosslinking agent, a general-purpose one used in the production of polyurethane foam can be used, and is not particularly limited.

  The polyurethane foam raw material according to the present invention can further be blended with various additives usually used for the production of polyurethane foam. Specific examples include foaming agents, colorants such as pigments, fillers such as calcium carbonate, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, conductive materials such as carbon black, and antibacterial agents. It is done. Among these, as the blowing agent, conventionally known general blowing agents such as water and methylene chloride can be used, but water is preferably used. The blending amount of the foaming agent, particularly water, can be 1.0 to 5.0 parts by mass with respect to 100 parts by mass of the polyol.

  The toner seal material of the present invention can be produced according to a conventional method using the above polyurethane foam raw material. The mixing method of the polyurethane foam raw material may be either a commonly used one-shot method or prepolymer method. In addition, as a method for producing polyurethane foam by foaming, a slab stock method, a casting method such as spray coating or roll coating, a molding method for molding in a mold, a dispenser method for casting from a thin nozzle, or the like can be employed.

The air permeability of the toner seal material of the present invention is 5 cc / cm ² / sec. By adjusting the MDI ratio and the amount of the crosslinking agent. Hereinafter, in particular, 0.5 to 1 cc / cm ² / sec. Can be about. In addition, the toner seal material of the present invention has a fine cell structure in which the number of cells is 65 cells / inch or more, particularly about 70 to 80 cells / inch by miniaturizing cells by adjusting the MDI ratio. It is preferable to have. With such a low air permeability and a fine cell structure, excellent toner sealing performance can be obtained.

Further, the density of the toner seal material of the present invention can be usually about 28 to 32 kg / m ³ . Furthermore, the hardness (25% hardness) of the toner seal material of the present invention can be about 100 to 160 N in the above density range. The density and hardness of these toner seal materials can be evaluated according to JIS K 6400. In the present invention, a toner sealing material satisfying the above-mentioned various properties can be obtained by adjusting the blending ratio of the constituent components of the polyurethane foam raw material.

Hereinafter, the present invention will be described in more detail with reference to examples.
Polyurethane foam raw materials shown in the following table were mixed and foamed by a one-shot method to obtain polyurethane foam. The results of evaluating the obtained polyurethane foams according to the following are also shown in the following table.

<Breathability evaluation>
The air permeability of each of the obtained polyurethane foams was measured with a JIS L 1004 fragile type with a foam thickness of 10 mm. Breathability is 1 cc / cm ² / sec. The following cases are designated as と し, and 1 cc / cm ² / sec. The case of exceeding X was set as x.

<Print performance evaluation>
Using each of the obtained polyurethane foams, a toner sealing material having a thickness of 20 mm × 200 mm × 10 mm was prepared, and the printing performance was evaluated. As for the printing performance, the case where there was no printing omission at the time of printing was marked with ◎, and the case where it was marked with x.

<Foam foam evaluation>
The foamability of each obtained polyurethane foam was evaluated. As for foamability, when foam is well formed and there is healthy foam, ◎, when foam is well formed but there is no healthy foam, ○, there is a defect in foam formation such as cracks in foam The case was marked with Δ, and the case where no foam was formed was marked with ×.

<Form elongation evaluation>
About each obtained polyurethane foam, elongation rate was evaluated based on JISK6400-5.3. The case where the elongation was 80% or more was rated as ◎, the case where it was 70% or more and less than 80%, and the case where it was less than 70%.

<Number of cells>
The test piece horizontally cut according to the growth direction of each obtained polyurethane foam block was observed with a stereomicroscope, the number of cells in the range of 1 inch in length was measured, and the average value of the three measured values was obtained. As for the foam appearance, the case where the number of cells is 65 / inch or more is indicated by ◎, the case of 60-64 / inch is indicated by ◯, and the case of 59 / inch or less is indicated by ×.

＊１）ダイマー酸ポリエステルポリオール，日立化成ポリマー（株）製，「ＴＥＳＬＡＣ２４５８」（数平均分子量：２５００，水酸基価：７５ｍｇ−ＫＯＨ／ｇ）
＊２）ＴＤＩ，三井化学ポリウレタン（株）製，「コスモネートＴ８０」
＊３）ＭＤＩ，住化バイエルウレタン（株）製，「４４Ｖ２０」（クルードＭＤＩ）
＊４）反応性アミン，エアープロダクツジャパン（株）製，「ＤＡＢＣＯ ＮＥ３００」
＊５）シリコーン，モメンティブ・パフォーマンス・マテリアルズ・ジャパン合同会社製，「ＮＩＡＸ ＳＩＬＩＣＯＮＥ Ｌ−５３４０」
＊６）架橋剤，三井化学（株）製，「アクトコールＴ８８０」

* 1) Dimer acid polyester polyol, manufactured by Hitachi Chemical Co., Ltd., “TESLAC2458” (number average molecular weight: 2500, hydroxyl value: 75 mg-KOH / g)
* 2) TDI, manufactured by Mitsui Chemicals Polyurethanes, Cosmonate T80
* 3) MDI, Sumika Bayer Urethane Co., Ltd., “44V20” (crude MDI)
* 4) Reactive amine, manufactured by Air Products Japan, "DABCO NE300"
* 5) “NIAX SILICON L-5340”, manufactured by Silicone, Momentive Performance Materials Japan GK.
* 6) Cross-linking agent, manufactured by Mitsui Chemicals, "Accor T880"

  As shown in the above table, in each example in which dimer acid polyol is used as a polyol, MDI in isocyanate is in a predetermined ratio, and a reactive amine and a foam stabilizer are used in a predetermined amount as a catalyst, It was confirmed that good toner sealing performance can be obtained without the occurrence of defects due to poor foaming.

  On the other hand, in Comparative Example 1, the ratio of MDI in the isocyanate is too high and the foam is not sufficiently stretched. In Comparative Example 2, the ratio of MDI in the isocyanate is too low and the number of cells is small. Appearance deteriorated.

Claims (3)

A polyurethane foam obtained by foaming a polyurethane foam raw material containing a polyol, an isocyanate, a catalyst and a foam stabilizer,
The polyol is a dimer acid polyol, the ratio of diphenylmethane diisocyanate in the isocyanate is 55 to 75% by mass, the catalyst is a reactive amine, and the polyurethane foam raw material is 100 parts by mass of the polyol. , polyurethanes the reactive amine at 0.2 to 0.5 parts by mass, the foam stabilizer at 3 to 5 parts by weight, a crosslinking agent at from 1 to 3 parts by weight, characterized in that it comprises respectively Form. The polyurethane foam according to claim 1, wherein the ratio of diphenylmethane diisocyanate in the isocyanate is 65 to 70 mass%. The polyurethane foam has an air permeability of 5 cc / cm ² / sec. The polyurethane foam according to claim 1 or 2 , wherein the number of cells is 65 / inch or more.