JP2005182072A5 - - Google Patents

Description

Rubber member for electrophotography

  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. .

A first aspect of the present invention that solves the above problems is a long-chain polyol comprising 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 6 to 8 mmol / g, and a polyisocyanate. And a polyurethane obtained by using a short-chain polyol having a molecular weight of less than 500, and the main component of the long-chain polyol is at least one of 1,9-nonanediol and methyl-1,8-octanediol and adipic acid A rubber elastic body which is a polyester polyol by condensation, 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 rubber elastic body has a rebound resilience of 10 ° C. of 15% or more and a rebound resilience of 50 ° C. of 70% or less. The electrophotographic rubber member is characterized in that the minimum resilience value in the temperature range of −20 ° C. to 60 ° C. is 0 ° C. or less .

A second aspect of the present invention is the rubber member for electrophotography according to the first aspect, wherein the main component of the polyisocyanate is diphenylmethane diisocyanate.

According to a third aspect of the present invention, there is provided the rubber member for electrophotography according to the first or second aspect, wherein the main component of the short-chain polyol is 1,3-propanediol.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the short-chain polyol contains trimethylolethane.

According to a fifth aspect of the present invention, there is provided the electrophotographic rubber member according to any one of the first to fourth aspects, wherein the rubber member has a blade shape.

  In the present invention, a 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 6 to 8 mmol / g is used as a material for the rubber elastic body.

That is, in the present invention, when a polyester polyol having an ester concentration of 6 to 8 mmol / g and a polyester polyol having an ester concentration lower than that of a conventionally used polyol is used, the temperature dependence of the resilience is reduced and the temperature is low. with rebound resilience is ensured to some extent while suppressing an increase in the impact resilience at high temperatures Ki out to reduce the chipping of the edge, in terms of achieving both the temperature dependence of such resilience and machine械的strength Is preferred.

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.

The polyester polyol used in the present invention is a polyester polyol obtained by dehydration condensation of diols such as 1,9-nonanediol and methyl-1,8-octanediol and adipic acid. 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. Specific examples of the polyester polyol obtained by dehydration condensation include nonanediol adipate and 2-methyl-1,8-octanediol adipate.

As the polyester polyol used in the present invention, a polyester polyol having the above-described polyester polyol as a main component and a part of which is substituted with another glycol or diacid group acid can be suitably used.

Other polyester polyols used in the present invention include ethylene glycol, butanediol, hexanediol, nonanediol, decanediol, 3-methyl-1,5-pentanediol, neopentylglycol, 2,4-diethyl-1, Diols such as 5-pentanediol, butylethylpropanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, and adipic acid, azelaic acid, sebacic acid, dimer acid, hydrogenated dimer acid, etc. What has the ester density | concentration which satisfies the conditions mentioned above in combination with a dibasic acid can be mentioned. Specifically , decanediol adipate, hexanediol azelate, nonanediol azelate, 2-methyl-1,8-octanediol azelate, decanediol azelate, butanediol sebacate, hexanediol sebacate, nonanediol seba Examples thereof include Kate, 2-methyl-1,8-octanediol sebacate, decanediol sebacate, dimer acid esters and hydrogenated dimer acid esters of various glycols. 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 to form 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.

  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 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.

(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 and 2 have remarkably low 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 rebound 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 and 2 showed stable cleaning characteristics against temperature change, good cleaning characteristics at low temperature, and good edge durability at high temperature use. . 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.