JP2005182072A - Rubber member for electrophotographic use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber member for electrophotographic use, the member having resilience remaining satisfactorily stable over changes in environmental conditions. <P>SOLUTION: The rubber member is a rubber elastic material, comprising polyurethane which is obtained by using a long-chain polyol and comprising a polyester polyol having 500 to 5,000 number average molecular weight and 6 to 8 mmol/g ester concentration defined by Formula (1): concentration of ester(mmol/g)=(number of moles of ester group)/(weight of polyester polyol), polyisocyanate, and a short-chain polyol having <500 molecular weight, wherein the long-chain polyol essentially comprises polyester polyol prepared by condensation of at least either 1,9-nonanediol or methyl-1,8-octanediol with adipic acid. The material has ≤ 55% for ΔRb expressed by Formula (2): ΔRb(%)=Rb<SB>T50</SB>-Rb<SB>T10</SB>, wherein Rb<SB>T10</SB>and Rb<SB>T50</SB>represent the resilience of the rubber elastic material at 10°C and 50°C, respectively. The rubber elastic material has ≥15% resilience at 10°C, and ≤70% resilience at 50°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber member for electrophotography used in a cleaning unit, a charging unit, a developing unit, a transfer unit, a paper feeding unit, etc. in electrophotography, and in particular, a toner image such as a photoreceptor or a transfer belt in electrophotography. The present invention relates to an electrophotographic rubber member such as a cleaning member that removes toner on a toner image carrier that is formed and then transfers the toner image to a transfer material, a developing member that is used in a developing unit, and a charging member that charges a photoreceptor.

  In general, in an electrophotographic process, at least charging, exposure, development, transfer, and cleaning processes are performed on an electrophotographic photosensitive member. In such an electrophotographic process, a toner image is formed and then the toner image is transferred to a transfer material. The cleaning member removes the toner on the toner image carrier, the developing member used in the developing unit, and the charging member that charges the photosensitive member. For example, polyurethane is used.

  This is because polyurethane has good abrasion resistance, has sufficient mechanical strength without adding a reinforcing agent, and is non-staining.

  However, it is known that the physical properties of polyurethane have temperature dependence. The temperature dependence is particularly manifested in the resilience and is a problem in cleaning particularly when a cleaning blade is made of polyurethane. That is, when the impact resilience is lowered at a low temperature, a cleaning failure is caused.

  By the way, the recent improvement in image quality in electrophotographic technology has made it possible to reduce the particle size of the toner, and there is a demand for a blade with higher functionality.

  In view of such circumstances, an object of the present invention is to provide a rubber member for electrophotography that has sufficiently stable rebound resilience even when the environment changes, and can be a highly functional cleaning blade or the like. .

  The first aspect of the present invention that solves the above-mentioned problems is obtained by using, as a long-chain polyol, a polyester polyol having a number average molecular weight of 500 to 5000 and an ester concentration defined by the following formula in the range of 2 to 8 mmol / g. The rubber member for electrophotography is a rubber elastic body made of polyurethane.

  A second aspect of the present invention is the rubber member for electrophotography according to the first aspect, wherein the polyester polyol is obtained by dehydration condensation of a diol component and a dibasic acid.

  According to a third aspect of the present invention, in the first aspect, the polyester polyol is obtained by copolymerizing a lactone with a dehydration condensation of a diol component and a dibasic acid or by dehydration condensation with a lactone. An electrophotographic rubber member characterized by being added.

  According to a fourth aspect of the present invention, there is provided the electrophotographic rubber member according to any one of the first to third aspects, wherein the long-chain polyol in the polyurethane is 60 to 80% by weight.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the rubber elastic body has a rebound resilience minimum value in a temperature range of −20 ° C. to 60 ° C. of 0 ° C. or less. It is in the rubber member for electrophotography.

A sixth aspect of the present invention is represented by the following formula when the rebound resilience at 10 ° C. and 50 ° C. of the rubber elastic body is Rb _T10 and Rb _T50 , respectively, in any of the first to fifth aspects. ΔRb is an electrophotographic rubber member characterized in that it is 55% or less.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the rubber elastic body has a 10 ° C. rebound resilience of 15% or more and a 50 ° C. rebound resilience of 70% or less. The rubber member for electrophotography is a feature.

  An eighth aspect of the present invention is the rubber member for electrophotography according to any one of the first to seventh aspects, wherein the rubber elastic body has a hardness of 50 to 90 ° according to JIS A.

  According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the polyurethane uses a polyester polyol having an ester concentration in the range of 6 to 8 mmol / g. It is in a rubber member for electrophotography.

  According to a tenth aspect of the present invention, in the ninth aspect, the polyurethane is composed of a long-chain polyol composed of the polyester polyol, a polyisocyanate, and a short-chain polyol having a molecular weight of less than 500. It is in a rubber member for electrophotography.

  An eleventh aspect of the present invention is the polyester polyol according to the tenth aspect, wherein the main component of the long-chain polyol is a condensation of at least one of 1,9-nonanediol and methyl-1,8-octanediol with adipic acid. The rubber member for electrophotography is characterized by the above.

  A twelfth aspect of the present invention is the rubber member for electrophotography according to the tenth or eleventh aspect, wherein the main component of the polyisocyanate is diphenylmethane diisocyanate.

  A thirteenth aspect of the present invention is the rubber member for electrophotography according to any one of the tenth to twelfth aspects, wherein the main component of the short-chain polyol is 1,3-propanediol.

  A fourteenth aspect of the present invention is the rubber member for electrophotography according to any one of the tenth to thirteenth aspects, wherein the short-chain polyol contains trimethylolethane.

  According to a fifteenth aspect of the present invention, in any one of the first to fourteenth aspects, there is an electrophotographic rubber member characterized by having a blade shape.

  In the present invention, polyurethane obtained by using a polyester polyol having a number average molecular weight of 500 to 5000 and an ester concentration defined in the above formula in the range of 2 to 8 mmol / g is used as a material for the rubber elastic body.

  That is, in the present invention, when the polyester concentration is 2 to 8 mmol / g and the polyurethane using the polyester polyol having a lower ester concentration than the conventionally used polyol is used, the temperature dependence of the resilience is reduced, and in a low temperature range. This is based on the knowledge that the rebound resilience of the resin is ensured to some extent, and the rise of the resilience resilience in the high temperature range can be suppressed to reduce edge chipping and the like. In particular, an ester concentration of 6 to 8 mmol / g is suitable for achieving both mechanical strength and temperature dependency such as rebound resilience.

  In addition, it is better to use a polyester polyol obtained by dehydration condensation of a diol component and a dibasic acid as a polyol having such a predetermined ester concentration than a caprolactone-based diol conventionally used as a standard. I found out. However, even when a polyol other than the polyester polyol obtained by dehydration condensation between the diol component and the dibasic acid is used, the above-described characteristics can be obtained if the ester concentration falls within the predetermined range described above.

  Examples of the predetermined polyester polyol used in the present invention include ethylene glycol, butanediol, hexanediol, nonanediol, decanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2,4-diethyl 1,5. -Diols such as pentanediol, butylethylpropanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, and two such as adipic acid, azelaic acid, sebacic acid, dimer acid, and hydrogenated dimer acid What has ester concentration which satisfies the conditions mentioned above in combination with a basic acid can be mentioned. Specifically, nonanediol adipate, 2-methyl-1,8-octanediol adipate, decanediol adipate, hexanediol azelate, nonanediol azelate, 2-methyl-1,8-octanediol azelate, decanediol Azelate, butanediol sebacate, hexanediol sebacate, nonanediol sebacate, 2-methyl-1,8-octanediol sebacate, decanediol sebacate, dimer acid ester and hydrogenated dimer acid ester of various glycols, etc. Can be mentioned. Several types of diols and dibasic acids can be combined.

  Also, lactones such as ε-caprolactone and δ-valerolactone can be polyadded or copolymerized within the above-mentioned conditions. That is, when a diol component and a dibasic acid are subjected to dehydration condensation, a lactone is copolymerized into a random copolymer, or a polyol obtained by polyaddition of a lactone to a dehydrated condensation product is used. It can also be used. By using lactones in this way, the resilience at low temperatures can be further improved.

  Particularly suitable in terms of performance and cost are polyester polyols obtained by dehydrating condensation of diols such as 1,9-nonanediol and methyl-1,8-octanediol with adipic acid. Of course, those having these as the main components and having some components substituted with other glycols or dibasic acids can also be suitably used. Here, methyl-1,8-octanediol is an octanediol having a methyl group at a position other than 1 or 8, and a typical one is 2-methyl-1,8-octanediol. It is not limited to.

  Examples of the polyisocyanate to be reacted with the polyester polyol include 2,6-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), Examples include 3,3-dimethyldiphenyl-4,4′-diisocyanate (TODI). In particular, MDI is preferable in terms of performance and cost.

  In order to produce polyurethane using the above-described polyester polyol, polyisocyanate is blended and reacted with the polyester polyol and the short-chain polyol as the chain extender. For the reaction, a general method for producing polyurethane such as a prepolymer method or a one-shot method can be used. The prepolymer method is suitable for the present invention because a polyurethane having excellent strength and abrasion resistance is obtained, but is not limited by the production method.

  Here, the short-chain polyol has a number average molecular weight of 500 or less, for example, a straight chain having 2 to 12 carbon atoms in the main chain such as ethylene glycol, 1,3-propanediol, 1,4-butanediol. Chain glycols; diols having a side chain of 12 or less carbon atoms such as neopentyl glycol and 3-methyl-1,5-pentanediol; unsaturated groups of 12 or less carbon atoms such as 3-allyloxy-1,2-propanediol Diols having a group; and diols having 20 or less carbon atoms including aromatic rings such as 1,4-bis (hydroxyethoxy) benzene and paraxylene glycol; cycloaliphatic diols such as cyclohexanediol and cyclohexanedimethanol Diols, triols such as trimethylolethane, trimethylolpropane, glycerin, and pentae It can be mentioned tetrafunctional or higher polyols such as Lithol or sorbitol. Of course, these short-chain polyols may be used in combination of two or more.

  Particularly suitable in terms of performance and cost are 1,4-butanediol and 1,3-propanediol. In particular, 1,3-propanediol exhibits a further effect when combined with a polyol having an ester concentration of 6 to 8 mmol / g. Further, it is preferable to use trimethylolethane in combination as a trifunctional or higher functional polyol added to improve characteristics such as creep and stress relaxation.

  In the polyurethane used in the present invention, the long-chain polyol in the polyurethane is preferably 60 to 80% by weight.

  In the present invention, in addition to the above-mentioned predetermined polyester polyol, other polyols can be used in combination as long as the effects of the present invention are not impaired. The content of the polyester polyol is 90 to 30 in the long-chain polyol. It is preferable that it is weight%.

  The rubber hardness of the rubber-like elastic body of the present invention is preferably 50 to 90 ° according to JIS A.

  When the polyurethane of the present invention is used, the temperature dependence of the rebound resilience is remarkably small while maintaining the mechanical properties required as a rubber member for electrophotography, and particularly as a rubber member for electrophotography such as a cleaning blade. It is suitable for use.

  As described above, according to the present invention, it is possible to provide an electrophotographic rubber member that has sufficiently stable rebound resilience even when the environment changes, and can be a highly functional cleaning blade or the like.

  Hereinafter, the present invention will be described based on examples.

(Example 1)
A polyester polyol having a molecular weight of 2000 was obtained from 1,9-nonanediol and adipic acid. The ester concentration in the polyester polyol is 6.8 mmol / g.

  A test sample and a cleaning blade were produced by using the polyester polyol, MDI, and 1,4-butanediol / trimethylolpropane mixed solution as a chain extender to form a thermosetting polyurethane. The polyester polyol in the polyurethane was about 65% by weight.

(Example 2)
A polyester polyol having a molecular weight of 2000 was obtained from hexanediol and hydrogenated dimer acid. The ester concentration in the polyester polyol is 3.0 mmol / g.

  A test sample and a cleaning blade were produced in the same manner as in Example 1 except that this polyester polyol was used. The polyester polyol in the polyurethane was about 65% by weight.

(Example 3)
A polyester polyol having a molecular weight of 2000 was obtained from 1,9-nonanediol / 2-methyl-1,8-octanediol (molar ratio 65/35) and adipic acid. The ester concentration in the polyester polyol is 6.8 mmol / g.

  A test sample and a cleaning blade were produced by using the polyester polyol, MDI, and 1,3-propanediol / trimethylolethane mixed liquid as a chain extender to form a thermosetting polyurethane. The polyester polyol in the polyurethane was about 65% by weight.

Example 4
In Example 3, 25 weight% of ε-caprolactone was copolymerized to obtain a polyester polyol having a molecular weight of 2000. The ester concentration in the polyester polyol is 7.3 mmol / g.

  A test sample and a cleaning blade were produced by using the polyester polyol, MDI, and 1,3-propanediol / trimethylolethane mixed liquid as a chain extender to form a thermosetting polyurethane. The polyester polyol in the polyurethane was about 65% by weight.

(Comparative Example 1)
A test sample and a cleaning blade were produced in the same manner as in Example 1 except that a polyester polyol having a molecular weight of 2000 (ester concentration: 11.3 mmol / g) composed of ethylene glycol and adipic acid was used. The polyester polyol in the polyurethane was about 65% by weight.

(Comparative Example 2)
Example 1 was used except that a polyester diol having a number average molecular weight of 2000 (caprolactone A: ester concentration 8.5 mmol / g) obtained by adding ε-caprolactone to ethylene glycol as an initiator was used. Test samples and cleaning blades were produced. The polyester polyol in the polyurethane was about 65% by weight.

(Comparative Example 3)
Example 1 was repeated except that polyester diol (caprolactone B: ester concentration 7.6 mmol / g) having a number average molecular weight of 1500 obtained by adding ε-caprolactone to dodecane diol as an initiator was used. Test samples and cleaning blades were produced. The polyester polyol in the polyurethane was about 65% by weight.

(Test Example 1)
About the test sample of each Example and a comparative example, the impact resilience of 0 degreeC-50 degreeC was measured, and the temperature dependence was evaluated. The results are shown in Table 1 and FIG. The rebound resilience was determined by a Lüpke-type rebound resilience test apparatus based on JIS K6255. The rubber hardness was determined according to JIS K6253.

  From this result, the test samples of Examples 1 to 4 have remarkably small temperature dependence of rebound resilience as compared with those of Comparative Examples 1 to 3, ΔRb is 55% or less, and rebound resilience at 10 ° C. It was found that the resilience at 15 ° C. was 15% or more and 70% or less.

(Test Example 2)
Using the cleaning blades of the examples and comparative examples, the cleaning characteristics were evaluated under the conditions of LL (10 ° C., 15% RH), NN (23 ° C., 50% RH), and HH (35 ° C., 85% RH). The edge wear state was observed. The cleaning characteristics were performed using a spherical polymerization toner having an average particle diameter of 6 μm. The results are shown in Table 2. Moreover, the data of each impact resilience were shown together.

  From this result, it was found that the cleaning blades of Examples 1 to 4 showed stable cleaning characteristics against temperature changes, good cleaning characteristics at low temperatures, and good edge durability when used at high temperatures. . These samples had a value of ΔRb of 55% or less, a rebound resilience at 10 ° C. of 15% or more and a rebound resilience at 50 ° C. of 70% or less.

  On the other hand, in Comparative Example 1 having a high ester concentration, the edge wear state was good, but the cleaning at low temperature was poor. This sample had ΔRb of 55% or less, but the rebound resilience at 10 ° C. was less than 15%.

  In Comparative Example 2, it was found that cleaning at high temperatures was difficult. In this sample, ΔRb was 64% and the temperature dependence of the resilience was large, and the resilience at 50 ° C. exceeded 70%.

  Further, Comparative Example 3 was a polyurethane using a polyester polyol having an ester concentration of less than 8 mmol / g, but good cleaning could not be performed. In this sample, ΔRb was 38%, and the temperature dependence of the resilience was relatively small. The resilience at 50 ° C. was less than 70%, but the minimum value of the resilience was 20 ° C. and higher than 0 ° C.

  From these results, it was found that polyester-based urethanes made from polyethylene adipate or polycaprolactone had a small particle size and sphericity, which had a relatively large particle size and had good cleaning characteristics with conventional toners having a pulverized shape. Sufficient cleaning characteristics cannot be obtained for high toner, and it is better to use polyurethane that satisfies the conditions of the present invention for toner with such a small particle size and high sphericity. It turns out that it is obtained.

  The cleaning characteristics in the table are indicated by ◯ when the cleaning was good and by × when the cleaning was not possible. As for the edge wear state, the uniform wear that does not disturb the image is indicated as OK, and the non-uniform wear such as a defect causing a defect in the image is indicated as NG.

It is a graph which shows the result of a test example.

Claims (5)

Obtained by using a long-chain polyol composed of a polyester polyol having a number average molecular weight of 500-5000 and an ester concentration defined by the following formula in the range of 6-8 mmol / g, a polyisocyanate, and a short-chain polyol having a molecular weight of less than 500. And a rubber elastic body, wherein the main component of the long-chain polyol is a polyester polyol obtained by condensation of at least one of 1,9-nonanediol and methyl-1,8-octanediol with adipic acid, and When the rebound resilience at 10 ° C. and 50 ° C. of the rubber elastic body is Rb _T10 and Rb _T50 , respectively, ΔRb represented by the following formula is 55% or less and the rebound resilience at 10 ° C. of the rubber elastic body is 15 %, And the resilience at 50 ° C. is 70% or less, and the temperature range is −20 ° C. to 60 ° C. An electrophotographic rubber member having a minimum rebound resilience value of 0 ° C. or less.

2. The rubber member for electrophotography according to claim 1, wherein the main component of the polyisocyanate is diphenylmethane diisocyanate. 3. The rubber member for electrophotography according to claim 1, wherein the main component of the short-chain polyol is 1,3-propanediol. 4. The rubber member for electrophotography according to claim 1, wherein the short chain polyol contains trimethylolethane. 5. The rubber member for electrophotography according to claim 1, wherein the rubber member has a blade shape.

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