JP2001253927A - Cleaning blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning blade having excellent durability, and made of a polyurethane elastomer having high productivity. SOLUTION: The cleaning blade contains a polyurethane elastomer produced by reacting (a) a polyisocyanate component with (b) a high-molecular polyol component and (c) a low-molecular polyol component. The low molecular polyol component (c) is composed of (c1) a >=3 functional low-molecular polyol and (c2) ethylene glycol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for cleaning and removing toner remaining on the surface of a photoreceptor or a surface of a transfer belt after an image is transferred in an image forming apparatus such as a copying machine, a printer, a facsimile or the like by an electrophotographic process. About the blade.

[0002]

2. Description of the Related Art Generally, in an electrophotographic copying machine, toner is adhered to an electrostatic latent image formed on the surface of a photoreceptor and developed, and the toner image is transferred to recording paper. Copying is performed by fixing the image on recording paper. In such a copying process, since the toner remains on the surface of the photoreceptor on which the toner image has been transferred to the recording paper, it is necessary to remove the toner from the surface of the photoreceptor in order to perform sequential copying. Is used as a cleaning blade.

Conventionally, as a material for forming a cleaning blade, a molded article made of a polyurethane elastomer has been awarded because of its excellent mechanical strength such as abrasion resistance. Such polyurethane elastomers are
Usually, a urethane prepolymer is prepared from a high molecular weight polyol component and a polyisocyanate component, and a 1,4-
After adding a dihydric alcohol such as butanediol and a low molecular polyol composed of a trihydric or higher polyhydric alcohol such as trimethylolpropane and pentaerythritol, crosslinking in a predetermined mold, and post-crosslinking in a furnace, It is manufactured by aging at room temperature. However, conventionally known cleaning blades made of a polyurethane elastomer have not been sufficiently durable due to large edge wear due to long-term use.

As a method for improving the durability of such a polyurethane elastomer, there is known a method for improving the modulus in a large deformation region of a cleaning blade. For example, in Japanese Patent Application Laid-Open No. H5-150697, an equivalent ratio (-OH) / (-NC) of a hydroxyl group (-OH) of a polyol component and an isocyanate group (-NCO) of a polyisocyanate component at the time of forming a polyurethane elastomer is disclosed.
A method has been proposed in which O) is adjusted to 0.8 to 0.9 to increase crosslinks due to allophanate bonds and improve the modulus in the large deformation region. However, since the allophanate bond has a low formation rate, when the formation of the polyurethane elastomer is performed within the above-mentioned equivalent ratio,
The curing time until the polyurethane elastomer reaches a strength at which it can be released from the mold becomes extremely long, and the productivity is poor. Also,
If a long curing time is required, it may cause clouding of the molded product.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning blade made of a polyurethane elastomer having good productivity and having excellent durability.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have focused on the constituent components of the polyurethane elastomer and made intensive studies. As a result, the present inventors have achieved the above object with a polyurethane elastomer having the following constituent components. This led to the completion of the present invention.

That is, the present invention provides (a) a polyisocyanate component, (b) a polymer polyol component, and (c)
A cleaning blade containing a polyurethane elastomer obtained by reacting a low molecular polyol component, wherein (c) the low molecular polyol component comprises (c1) a trifunctional or higher functional low molecular polyol and (c2) ethylene glycol. It relates to a cleaning blade characterized by the following.

Conventionally, it has been known to use (c1) a trifunctional or higher-functional low-molecular polyol and a bifunctional low-molecular polyol as (c) a low-molecular polyol component. As one of (c2)
Ethylene glycol is exemplified, but if (c2) ethylene glycol is used alone as a bifunctional low molecular polyol, turbidity occurs in the molded sheet, and therefore (c2) ethylene glycol alone is used as a bifunctional low molecular polyol. It was never used, and even if it was used, it was only an example in which it was used in combination with 1,4-butanediol or the like. The present invention is characterized in that (c2) ethylene glycol, which has never been used alone as a bifunctional low molecular polyol, is used in combination with (c1) a trifunctional or higher functional low molecular polyol, It has been found that by selecting a specific low-molecular polyol, the modulus in the large deformation region is improved, the abrasion resistance of the polyurethane elastomer is improved, and the durability is improved. Also,
The cleaning blade of the present invention has a small set, and the set of the cleaning blade is improved. Furthermore, the cleaning blade of the present invention is disclosed in
Both the molding time and temperature can be set lower than those described in JP-A-0697, and the productivity is good.

[0009] Further, the polyurethane elastomer includes:
(A) a polyisocyanate component or an isocyanate-terminated urethane prepolymer obtained from (a) a polyisocyanate component and (b) a polymer polyol component;
It is obtained by reacting (b) a high molecular weight polyol component and / or (c) a low molecular weight polyol component, and comprises an isocyanate group (-NCO) and a hydroxyl group (-OH) which can form a urethane bond in the reaction. Equivalent ratio (-NC
O / -OH) is preferably 1.00 to 1.15.

[0010] The polyurethane elastomer may be the above-mentioned (a)
It is obtained by reacting a polyisocyanate component, (b) a high molecular polyol component and (c) a low molecular polyol component by various methods. When a polyurethane elastomer is finally obtained, the equivalent ratio (-NCO / -OH) is used. Is adjusted to the above range, the physical properties such as the curing speed and the permanent elongation of the polyurethane elastomer are improved.

When the equivalent ratio is reduced, physical properties such as permanent elongation tend to be deteriorated.
More preferably, it is set to 05 or more. On the other hand, when the equivalent ratio increases, the curing rate tends to be slow, and the moldability tends to be poor. Therefore, the equivalent ratio is more preferably 1.10 or less.

Also, the molar ratio of (c1) a trifunctional or higher functional low molecular polyol to (c2) ethylene glycol is represented by the following formula:
It is preferable to adjust (c1) / (c2) = 1/2 to 12. By using (c1) a trifunctional or higher-functional low molecular weight polyol and (c2) ethylene glycol in such a molar ratio, a polyurethane elastomer having a practical range of hardness, generally a Shore A hardness of 65 to 77, is obtained. can get. If the value of (c2) in the above molar ratio is small, the hardness tends to be low and desired physical properties tend not to be obtained. Therefore, the value of (c2) is more preferably 4 or more. On the other hand, when the value of (c2) in the molar ratio is large, the permanent elongation is large, the curing time tends to be long, and the productivity tends to be poor. Therefore, the value of (c2) is more preferably 10 or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The (a) polyisocyanate component, (b) high-molecular polyol component and (c) low-molecular polyol component constituting the polyurethane elastomer which is the main component of the cleaning blade of the present invention will be described.

As the polyisocyanate component (a), one or more of various types used for forming a polyurethane elastomer can be appropriately selected and used. For example, tolylene diisocyanate, 3,3'-dimethyl diphenyl diisocyanate, 4,4'-diphenyl methane diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate and the like can be mentioned. Of these, 4,4'-diphenylmethane diisocyanate is preferred.

As the polymer polyol component (b), one or more of various kinds used in the formation of the polyurethane elastomer can be appropriately selected and used. For example, polyether polyol, polyester polyol and the like can be exemplified.

Examples of the polyether polyol include polyoxypropylene obtained by adding propylene oxide to one or more polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. Polyols, polyoxyethylene polyols obtained by adding ethylene oxide, polyols obtained by adding butylene oxide, styrene oxide, and the like, and obtained by adding tetrahydrofuran to the polyhydric alcohol by ring-opening polymerization. Examples thereof include polyoxytetramethylene polyols. Also,
Copolymers using two or more of the above cyclic ethers can also be exemplified.

Examples of the polyester polyol include one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, trimethylolpropane, pentaerythritol and other low molecular weight polyhydric alcohols. Condensation polycondensation with one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, hydrogenated dimer acid or other low molecular dicarboxylic acids or oligomeric acids Examples thereof include ring-opening polymers of cyclic esters such as propiolactone, caprolactone, and valerolactone using the above-mentioned polyhydric alcohol as an initiator. In addition to the above, (b) as the polymer polyol,
For example, polycarbonate diol and the like can be exemplified.

As the polymer polyol (b) of the present invention, polyester polyols are preferred, and adipic acid-based polyester polyols and polycaprolactone-based polyester polyols are particularly preferred.

The number average molecular weight of the high molecular weight polyol component (b) is usually preferably about 500 to 3000. The number of functional groups in the polymer polyol component (b) is not particularly limited, and bifunctional or trifunctional or higher functional groups can be appropriately selected and used depending on the number of functional groups such as glycol. Usually, it is preferable to use a bifunctional (b) polymer polyol component.

(C) As the low molecular polyol component,
(C1) Trifunctional or higher functional low molecular polyol and (c2) ethylene glycol are used. (C1) As the trifunctional or higher functional low molecular polyol, one or more of various types used for forming a polyurethane elastomer having a molecular weight of less than 500 can be appropriately selected and used.
(C1) Examples of the trifunctional or higher functional low molecular polyol include trifunctional ones such as 1,1-trimethylolpropane, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, Methylolethane, 1,1,1-tris (hydroxyethoxymethyl) propane and the like can be mentioned, and tetra- or more-functional diglycerin, pentaerythritol and the like can be mentioned.

(A) a polyisocyanate component,
The method for producing the polyurethane elastomer from the (b) high molecular polyol component and the (c) low molecular polyol component is not particularly limited, and various methods can be employed.

For example, a prepolymer method in which (a) an isocyanate-terminated urethane prepolymer obtained from a polyisocyanate component and (b) a high-molecular-weight polyol component is reacted with (c) a low-molecular-weight polyol component, A pseudo prepolymer method in which (b) a high-molecular polyol component and (c) a low-molecular polyol component are reacted, (a) a polyisocyanate component, (b) a high-molecular-weight polyol component and (c) a low-molecular polyol component which are simultaneously reacted. A shot method or the like can be adopted. Among these polyurethane elastomer production methods, the prepolymer method or the pseudo prepolymer method is
This is preferable because there is no problem such as air bubbles entering the sheet during molding.

The isocyanate-terminated urethane prepolymer in the prepolymer method and the pseudo prepolymer method is as follows:
It is preferable that the isocyanate group content is adjusted to 8 to 20%.

In the pseudo prepolymer method, (b) the high molecular polyol component used for producing the isocyanate-terminated urethane prepolymer and (b) the high molecular polyol component used for curing the urethane prepolymer may be the same, It may be different.

In the pseudo prepolymer method, the (b) high molecular polyol component used for curing is preferably 60 to 80% by weight of the entire (b) high molecular polyol component constituting the polyurethane elastomer. The ratio of the (b) high molecular polyol component to the (c) low molecular polyol component used for curing is preferably such that (c) the low molecular polyol component is 10% by weight or less.

As described above, when producing a polyurethane elastomer, (a) a polyisocyanate component or an isocyanate group (-NCO) of an isocyanate-terminated urethane prepolymer and (b) a high molecular polyol component and / or (c) a low The hydroxyl group of the molecular polyol component (-
OH) is equal to (-NCO / -OH) 1.00 to 1.
It is preferably set to 15.

Production (curing) of polyurethane elastomer
At that time, a curing catalyst may be used. For example, amine catalysts include triethylenediamine, dimethylaminohexanol and the like, imidazole catalysts such as 2-methylimidazole and 1,2-dimethylimidazole, and metal catalysts such as lead octylate and dibutyltin laurate. When a curing catalyst is used, the amount of the curing catalyst is usually 0.1 part by weight based on 100 parts by weight of the polyurethane elastomer {total of components (a), (b) and (c)}.
About 001 to 0.05 parts by weight, preferably 0.005 to 0.0 parts by weight.
The range is 3 parts by weight.

The method of forming the cleaning blade is not particularly limited, but when the polyurethane elastomer is produced by the pseudo-prepolymer method or the prepolymer method, the curing agent is mixed with the curing catalyst when reacting the prepolymer with the curing agent. After stirring, these are cast by a casting method of injecting them into a predetermined mold, or by a centrifugal molding method using a centrifugal molding machine.

In molding, it is also possible to insert a connector which has been subjected to an adhesive treatment in advance. The curing temperature is a predetermined temperature, usually about 120 to 160 ° C.

In forming the cleaning blade, additives such as an antistatic agent and a lubricant can be contained in addition to the polyurethane elastomer, and these additives are mixed with the curing catalyst. After the primary curing as described above, it is usually possible to perform secondary curing by heating according to a conventional method.

The polyurethane elastomer thus obtained is cut to meet the specifications of the electrophotographic copying machine to be used, and used as a cleaning blade.

[0032]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. In each example, parts means parts by weight.

Example 1 133.3 parts of a bifunctional polylactone polyol (manufactured by Daicel Chemical Co., Ltd., trade name: Placcel 220N, number average molecular weight: 2,000, hydroxyl value: 56.1) was stirred and heated under reduced pressure at 70 ° C. for 3 hours. After dehydration, the reaction vessel was charged, and 100 parts of 4,4'-diphenylmethane diisocyanate was further added to the reaction vessel.
After stirring for an hour, an isocyanate-terminated urethane prepolymer having an isocyanate group content of 12% was prepared. The isocyanate group content was measured by the dibutylamine method.

Separately, 150.2 parts of the above-mentioned bifunctional polylactone polyol (manufactured by Daicel Chemical Co., Ltd., trade name: Placcel 220N, number average molecular weight: 2,000, hydroxyl value: 56.1)
In a separate container, 3.6 parts of trimethylolpropane and 11.7 parts of ethylene glycol were stirred and heated at 100 ° C. for 1 hour under reduced pressure, dehydrated, charged in a glass reaction container, and placed in a nitrogen atmosphere. The mixture was stirred and mixed at 100 ° C. until the mixture became colorless and transparent. Further, 0.005 part of triethylenediamine was further added as a curing catalyst to prepare a curing agent component (OH component). The equivalent ratio of the isocyanate group (-NCO) of the urethane prepolymer and the hydroxyl group (-OH) of the curing agent component (-NCO / -O
H) was adjusted to be 1.10.

The urethane prepolymer and the curing agent component are supplied to a mixing head while being heated to 60 ° C.
While mixing and stirring, the mixture was poured into a mold heated to 140 ° C. in advance to mold a polyurethane elastomer. Next, the molded product was taken out of the mold and heated at 110 ° C. for 24 hours to perform secondary curing.

Examples 2 to 3 and Comparative Examples 1 to 4 The same procedures as in Example 1 were carried out except that the amounts and proportions of the respective components of the polyurethane elastomer were changed as shown in Table 1.
A cleaning blade was manufactured in the same manner as described above. In addition,
In Comparative Example 3, the curing speed was slow, the polyurethane elastomer could not be molded, and no cleaning blade was obtained.

[Evaluation of Physical Properties]: The following physical properties of the obtained cleaning blade were evaluated. Table 1 shows the results.

The physical properties were measured in accordance with JIS K7312. However, the hardness (according to Shore A hardness) and the rebound resilience were measured for a sheet having a thickness of 1.5 to 2 mm with a thickness of 12 to 15 mm.
mm (the sample is 35 mm square). For the measurement of the rebound resilience (%), a measuring device of JIS K6301 (Lupke type measuring device) was used. The permanent elongation was measured by marking a mark (100 mm) on a sample (150 mm × 10 mm), extending 100% for 10 minutes, releasing the mark, measuring the mark 10 minutes after release, and measuring the residual strain rate for 100 mm. It was measured.

[Evaluation of durability]:
The blade was attached to a plain paper copier manufactured by Minolta Co., Ltd., and a black / white 7% character chart was used as an image to be copied at room temperature and normal humidity at a rate of 25 sheets / min. Every 20 hours, the time required for the amount of wear of the edge of the blade to reach 50 μm was checked. Table 1 shows the results. Note that Table 1 shows that
The estimated number of sheets that can be copied normally is also shown.

[0040]

[Table 1] In the table, a: MDI of the prepolymer indicates 4,4'-diphenylmethane diisocyanate.

The prepolymer b: 2PCL is a bifunctional polylactone polyol (Placcel 220N, trade name, manufactured by Daicel Chemical Industries, Ltd., number average molecular weight 2,000, hydroxyl value 56.
1) is shown. However, 2PCL of Comparative Example 4 was a bifunctional polylactone polyol (manufactured by Daicel Chemical Co., Ltd., trade name: Placcel 220N, number average molecular weight 2000, hydroxyl value 56.
1) and a bifunctional polylactone polyol (Placcel 210N, manufactured by Daicel Chemical Co., Ltd., number average molecular weight 100)
0, a hydroxyl value of 112.2), the number average molecular weight of which is adjusted to 1900.

The polymer polyol b: 2PCL is a bifunctional polylactone polyol (Placcel 220N, manufactured by Daicel Chemical Co., Ltd., number average molecular weight 2,000, hydroxyl value 5)
6.1) is shown. However, 2PCL of Comparative Example 4 is a bifunctional polylactone polyol (Placcel 220N, trade name, manufactured by Daicel Chemical Industries, Ltd., number average molecular weight 2,000, hydroxyl value 5).
6.1) and a bifunctional polylactone polyol (manufactured by Daicel Chemical Co., Ltd., trade name: Placcel 210N, number average molecular weight: 100)
0, a hydroxyl value of 112.2), the number average molecular weight of which is adjusted to 1450.

The polymer polyol b: 3PCL is a trifunctional polylactone polyol (Placcel 320, trade name, manufactured by Daicel Chemical Industries, Ltd., number average molecular weight 2000, hydroxyl value 84.
2) and trifunctional polylactone polyol (Daicel Chemical Co., trade name: Placcel 312, number average molecular weight 1250,
This is a blend having a hydroxyl value of 134.6), the number average molecular weight of which is adjusted to 1900.

TMP: trimethylolpropane, EG:
Ethylene glycol, BD: represents 1,4-butanediol.

As is clear from Table 1, the cleaning blades of the present invention shown in Examples have excellent physical properties.
It can be seen that the abrasion time of the edge is longer than that of the comparative example and the durability is excellent. In addition, the equivalent ratio (-NCO / -O
Since H) is within the predetermined range, the curing speed is also good.
In Comparative Example 3, the equivalent ratio was out of the predetermined range, and curing could not be performed in the same time as the other examples.

The durability and the predicted number tend to decrease as the hardness decreases, and the predicted number tends to decrease. Example 1 has a hardness of 65, Comparative Example 2 has a hardness of 77, and Example 1 has the same or higher durability and predicted number of sheets although it is lower than Comparative Example 2. In comparison between the example having the same hardness and the comparative example, the durability and the predicted number of sheets are about twice as good as those of the comparative example.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H032 BA05 BA09 BA18 BA30 2H034 BF03 BF05 4J034 BA07 BA08 CA01 CA04 CA05 CB03 CB04 CB05 CB07 CC01 CC02 CC03 DA01 DB01 DB03 DB04 DB05 DC01 DC02 DC03 DC12 DC37 DC42 DF01 DF02 DF02 DF02 DF17 DF21 DF22 DG01 DG02 DG03 DG04 DG05 DG06 DG14 DG15 DG16 HA01 HA06 HA07 HC11 HC12 HC13 HC52 HC61 HC63 HC64 HC66 HC67 HC71 JA41 JA42 KA01 QA03 QA07 QB15 RA11 RA14

Claims (3)

[Claims] (1) a polyisocyanate component, (b)
In a cleaning blade comprising a polyurethane elastomer obtained by reacting a high molecular polyol component and (c) a low molecular polyol component, the (c) low molecular polyol component comprises (c1) a trifunctional or higher functional low molecular polyol and ( c2) A cleaning blade comprising ethylene glycol. 2. A polyurethane elastomer comprising: (a) a polyisocyanate component or an isocyanate-terminated urethane prepolymer obtained from (a) a polyisocyanate component and (b) a polymer polyol component; and (b) a polymer polyol component and / or Or (c) an isocyanate group (-N) which is obtained by reacting a low molecular weight polyol component and can form a urethane bond in the reaction.
CO) and hydroxyl group (-OH) equivalent ratio (-NCO / -O
The cleaning blade according to claim 1, wherein H) is 1.00 to 1.15. 3. The molar ratio of (c1) a trifunctional or higher functional low molecular weight polyol to (c2) ethylene glycol is as follows:
1) / (c2) = 1/2 to 12
The cleaning blade as described.